CONSTRUCTION TECHNOLOGY

By:

Indrie Maulina Utami

Lutfi Miyanti

Sinta Larasati

Construction Management 2010

STATE POLYTECHNIC OF JAKARTA

INTRODUCTION

There are two general method which is used construction of buildings:

1. Conventional or traditional method2. Modern or industrialized method

Conventional or traditional method are studied with intention of forming a sound knowledge base before proceeding to studies of advanced techniques. Initial studies of building construction concentrate on the smaller type of structure, we should know conventional or traditional method before we know about modern or industrialized method. These industrialized methods are usually a rationalized manufacturing process used to produce complete elements.

THE BUILDING TEAM

Building need team work in which each member has an important role.

Building ownerThe client; An owner-builder is defined as a person who constructs or renovates a domestic building on his or her own land, who is not in the business of building, the person or organization who finances and commission the work. The directly or indirectly employ all the personnel, with particular responsibility for appointing the planning supervisor (usually the architect) and nominating the principal contractor-see construction (design and management) regulation 1994. It is important to consult your building surveyor at the outset to determine if a certificate of consent is required.  This may be a private building surveyor or a municipal building surveyor.

ArchitectEngaged by building owner as agent to design, advise, and ensure that the project is kept within cost and complies with the design. An architect is a person trained in the planning, design and oversight of the construction of buildings, and is licensed to practice architecture. To practice architecture means to offer or render services in connection with the design and construction of a building, or group of buildings and the space within the site surrounding the buildings, that have as their principal purpose human occupancy or use. Etymologically, architect derives from the Latin architectus, itself derived from the Greek arkhitekton (arkhi-, chief + tekton, builder), i.e. chief builder.

Clerk of worksIs a person employed by the architect or client on a construction site. The role is primarily to represent the interests of the client in regard to ensuring the quality of both materials and workmanship are in accordance with the design information such as specification and engineering drawings, in addition to recognized quality standards. The role is defined in standard forms of contract such as those published by the Joint Contracts Tribunal. Historically the Clerk of Work was employed by the architect on behalf of a client, or by Local Authorities to oversee public works.

Employed on large contract as a architect on site representative. The main function is to liaise between architect and main contractor and to ensure that construction proceed in accordance with the design. They can offer advice but directives must be through the architect.

Quantity surveyorEngaged to prepare cost evaluation and bills of quantities, check tenders, prepare interim valuation, effect cost controls, and advice the architect on the cost of variations.in the world of construction especially or in a project in general consist of several big jobs process, that is: planning process, execution process, supervision process. in this planning stage is quantity surveyor works. in planning stage there are a lot of team that impersonate, begin from; architect, civil engineer, geo tech engineer, water sanitation engineer, mechanical & electrical engineer and quantity surveyor. Job description from quantity surveyor among others:

1. in earliest stage quantity surveyor will have to do market survey to get building material materials price that he will use with will threaten technical specification and beefsteak document. a expert quantity surveyor can determine ingredient price turn ever he use previous.

2. in stage furthermore quantity surveyor have a duty to do calculation towards unit price analysis next job unit price appropriate project management wisdom. Sometimes in projects from government require use standard analysis appropriate. in private project are used analysis as according to wisdom and experience self belong labor coefficient and ingredient also very big the influence in determine job unit price.

3. after all has calculation process price is continued with put into job item in form bill of quantity standards every corporation. All job items must include in columns job description and mention materials specification or special things that must have required. Job item subdividing based on sequence or sequence job execution is of vital importance to prevent confusion that stump the interested parties.

4. important stage next that is has done calculation quantity each job from work pictures that prepared by each part has begun from architect, civil, geo tech, watsan, mechanical electrical. Calculation quantity must be done with tall accuracy and not include interest from several the interested parties.

5. as stage ends after got unit price, job item, and quantity next that is do multiplication between quantity and unit price in every job item. then add up each sub total in each lot job and add up sub be grand total most under table boq.

profession quantity surveyor frequently demanded loyalty existence and integrity towards company or where does he shelter body. in determine analysis, job item and quantity very make possible to do mark up that can harm one of the parties. This matter is of course is easy for quantity surveyor firm in hold commitment towards the job.

Consulting engineersEngaged to advise and design on a variety of specialist installations, e.g. structural, services security, etc. They are employed to develop that particular aspect of the design within the cost and physical parameters of the architect brief.

Principal or main contractorEmployed by the client on the advice of the architect, by nomination or competitive tendering they are required to administer the construction project within the architect’s direction. Chief contractor who has a contract with the owner of a project or job, and has the full responsibility for its completion. A prime contractor undertakes to perform a complete contract, and may employ (and manage) one or more subcontractors to carry out specific parts of the contract. Also called main contractor.

Contract’s manager or site agentOn large projects the main contractor’s representative on site, with overall responsibility for ensuring that work proceeds effectively and efficiently, i.e. in accordance with they design classification and to time. Sometimes known as general foreman, but this title is more appropriate on small to modest size contracts. A site manager is the person in charge of all on site operations, working with contractors and subcontractors and ensuring the building contract runs to schedule. A site manager controls all aspects of the site including planning work, arranging delivery of materials and managing a range of subcontractors, and is ultimately responsible for ensuring a contract is delivered on time. Site managers are employed mainly by building and construction companies, civil engineering firms and contractors. Many local authorities also employ site managers for the refurbishment of council homes and other council owned buildings..Typical work activities include:

ensuring the project runs to schedule and to budget, managing programmers of work, and finding solutions to problems that may cause delays, such as the late arrival of materials;

playing a major role in pre-site and on-site meetings with a range of professionals who work to ensure a building contract is successful, including quantity surveyors, contract administrators, site foremen, subcontractors, and the client who has commissioned the work;

maintaining strict quality control procedures - this necessitates regular testing of materials, visual inspections of work, and frequent tours of the site;

conducting regular site safety checks.Recent graduates are highly unlikely to be appointed in a full site manager role until they have the necessary site experience. However there are plenty of opportunities for assistant site managers or for other roles in the building project team, such as site engineer, that will allow graduates to gain the necessary skills and experience.

SurveyorEmployed by the main contractor to check work progress and assist the quantity surveyor in the preparation of interim valuation for stage payments and final accounts. May also be required to measure work done for bonus and subcontractor payments.

EstimatorPrepares unit rates for the pricing of tenders carries out pretender investigations into the cost aspects of the proposed contract. In statistics, an estimator is a rule for calculating an estimate of a given quantity based on observed data: thus the rule and its result (the estimate) are distinguished. This article discusses estimators and estimates that are point estimators; that is, they yield single-valued results, although this includes the possibility of single vector-valued results and results that can be expressed as a single function. This is in contrast to an interval estimator, where the result would be a range of plausible values (or vectors or functions). Statistical theory is concerned with the properties of estimators; that is, with defining properties that can be used to compare different estimators (different rules for creating estimates) for the same quantity, based on the same data. Such properties can be used to determine the best rules to use under given circumstances. However, in robust statistics, statistical theory goes on to consider the balance between having good properties, if tightly defined assumptions hold, and having less good properties that hold under wider conditions.

BuyerOrders materials, obtains quotation for the supply of materials and services.

AccountantAn accountant is a practitioner of accountancy which is the measurement, disclosure or provision of assurance about financial information that helps managers, investors, tax authorities and other decision makers make resource allocation decisions.Prepares and submits accounts to clients and makes payments to suppliers and subcontractor. May also have a costing the department which would allocate the labour and material costs to each contract to assist with the preparation of accounts.

AdministratorOrganizes the general clerical duties of the contractor’s office for the preparation of contract documents and payment of salaries, subcontractor and suppliers invoices, insurances and all necessary correspondence.

Assistant contract managerOften a trainee in the process of completing professional examinations. Assist with the general responsibility for administering site proceedings.

Nominated subcontractor Engaged by the client or architect for specialist construction or installation work, e.g. lifts, air conditioning, etc.

Domestic subcontractorEmployed by the principal contractor to assist with the general construction, e.g. ground workers, bricklayers, etc.

Operatives

The main work force on site, includes craftsmen, apprentices, and labourers. A specialist class for Engineers and Infiltrators. Operatives are masters at manipulating their environment to maximum advantage. Bonuses include reduced recharge on all tech attacks, and improvements to overload and sabotage. Operatives are often responsible for keeping the site tidy and looking after tools and equipment. Following instruction from skilled workers is an important part of the work.

SITE AND TEMPORARY WORKS

CHAPTER 1.1

SITE WORKS AND SETTING OUT

CLEARING THE SITE

This may involve the demolition of existing building the grubbing out of bushes or trees or the removal of soil to reduce levels. When the site is located in a wooded area, the first operation is to clear all timber, standing or fallen. If camouflage is necessary, trees or bush outside the designated cleared area should not be removed.

Demolition is a skilled occupation and should only be taken by an experience contractor. Construction equipment operations are usually the most rapid and efficient means of clearing a site. Use of the equipment is limited only by unusually large trees and stumps–terrain which hinders their maneuverability and   maintenance requirements. The construction equipment used includes bulldozers, winches, power saws, rippers, motor graders, and scrapers.

In addition, hand tools are used in certain clearing operations. Bush may be disposed of by burning on the site; however, check to see if a burn permit is required. This timber should be saved for possible use in construction of loading ramps.  All stumps, roots, boulders, vegetation, and rubbish must be excavated and moved clear of the site. The site must be clear from vegetable matter; this is effect to sterilize the ground or so will contain plant life and decaying vegetation. The side easily compressed and would be unsuitable for foundation.

SETTING OUT THE SITE

The first task is to establish a base line from which the whole of the building can be set out. The line must be clearly marked on-site, and can be re-establishing at any time. Setting out is the process by which is taken from the construction design drawings, and pegs, profiles or other marks are then set to control the construction works and ensure that each element of the works is constructed in the right position and to the correct level with a stout peg.

Learners will work with traditional methods to achieve an understanding of the essential mathematical and practical skills required for the Setting out process, including the application of basic principles of techniques to ensure appropriate levels of accuracy.

Construction projects are normally designed on a coordinate grid and calculations are carried out to convert these into a form useful for setting out. Learners must attain a reasonable standard of arithmetic and trigonometry in order to successfully complete this unit.

This is essentially a practical unit, through which learners will come to understand setting out as a key part of the construction process, and be able to carry out the standard tasks and calculations involved.

After the setting out the main building lines has been completed and checked, profile boards are set up. These are set up clear of the foundation trench and wall intersections.

ESTABLISHING A DATUM LEVELS

All levels in a building are taken from a fixed point called a datum. This point should now be establish, must be clearly marked on-site; wherever possible this should be related to an ordnance benchmark. Benchmarks are found cut or let into the sides of walls and buildings. Where there are no benchmark could be a post set in concrete or a concrete plinth set up onsite.

SLOPING SITES

Cut and fill in earthmoving is the process of constructing whereby the amount of material from cuts roughly equal or matches the amount of fill, so minimizing the amount of construction labor. This is the usual method and the most economical because the amount of cut can be replaced in the fill side, and not through away to useless.

Cut The advantage of this method is giving undisturbed soil in the whole of the side. But have the disadvantage; we must be pay more for removing the cut’s soil from the side. Cut sections are characterized by the roadway being lower in elevation than the surrounding terrain. From an operational standpoint there are unique environmental effects associated with cut sections. For example, air pollutants can concentrate in the valleys created by the cut section. Conversely, noise pollution is mitigated by cut sections since an effective blockage of line of sight sound propagation.

Fill Environmental effects of fill sections are typically favorable with respect to air pollution dispersal, but in the matter of sound propagation, exposure of nearby residents is generally increased, since sound walls and other forms of sound path blockage are less effective in this geometry.

There are a variety of reasons for creating fills, among them reduction of grade along a route or elevation of the route above water, swampy ground, or areas where snow drifts frequently collect. If the building sited on the filled area, either deep foundation would be needed or the risk of settlement at a later stage would have to be accepted.

CHAPTER 1.2

ACCOMMODATION, STORAGE AND SECURITY

The builder have to provide the best facilities which are economically possible for any particular contract, this should make good relationships between management and staff, should also reduce the loss of materials due to theft, accidental damage. This offers the client a competitive advantage with regards to creating parity amongst the various sub-contractors' labour and ex-pat work forces. This interaction with all stakeholders is important. The better accommodation, storage and security on a building site will make staff feel comfort so that the client will get better productivity.

ACCOMMODATION

Requirements will vary with regard to the number personnel on site and in some cases the anticipated duration of the contract.

Unit of staff accommodation usually come in one of two forms. It’s usually called camp construction:

Sectional timber hutsSectional timber huts are prefabricated to allow for ease of dismantling and assembly to facilitate the re-use on other sites. Huts should be designed, constructed and maintained with the same care as permanent buildings to ensure their use for many years. The anticipated use of each hut will govern the construction and facilities. Main work necessary like in the permanent building must be filled up.

Mobile caravans or cabinsCaravans and cabins are fully equipped with all necessary furniture. Transportation of caravans or cabins can be suitable vehicle, so it may move from place to another place. Whichever method is used the time taken to load, offload and position on site is considerably shorter than the time required to dismantle, transport and reassemble a sectional timber hut, but the initial capital outlay is higher.

Supply and build camps in accordance with each client's unique or specific requirements. Various camp options are offered, ranging from soft-walled tents to hard-walled permanent structures. Services that have an overriding goal of creating a 'home away from home' environment for all camp residents. Services include all aspects of cleaning and maintenance and HR administration.

Health, Safety and Welfare

General safety principles can help reduce workplace accidents. These include work practices, ergonomic principles, and training and education. Whether moving materials manually or mechanically, employees should be aware of the potential hazards associated with the task at hand and know how to exercise control over their workplaces to minimize the danger. When manually moving materials, employees should seek help when a load is so bulky it cannot be properly grasped or lifted, when they cannot see around or over it, or when a load cannot be safely handled. When an employee is placing blocks under raised loads, the employee should ensure that the load is not released until his or her hands are clearly removed from the load. Blocking materials and timbers should be large and strong enough to

support the load safely. Materials with evidence of cracks, rounded corners, splintered pieces, or dry rot should not be used for blocking. Handles and holders should be attached to loads to reduce the chances of getting fingers pinched or smashed. Workers also should use appropriate protective equipment. For loads with sharp or rough edges, wear gloves or other hand and forearm protection. To avoid injuries to the hands and eyes, use gloves and eye protection. When the loads are heavy or bulky, the mover should also wear steel-toed safety shoes or boots to prevent foot injuries if the worker slips or accidentally drops a load.

STORAGE

The efficient handling and storing of materials is vital to industry. These operations provide a continuous flow of raw materials, parts, and assemblies through the workplace, and ensure that materials are available when needed. Yet, the improper handling and storing of materials can cause costly injuries.

The type of storage facilities required of any particular material will depend upon the following factors:

Durability – will it need protection from the elements? Vulnerability to damage Vulnerability to theft

Cement, plaster, and lime supplied in bag form require a dry store free from draughts which can bring in most air and may cause an air set of material. These materials should not be stored for long periods on site. Aggregates such as sand and ballast require a clean firm base to ensure that foreign matter is not included when extracting materials from the base of stock pile. Different materials and grades must be kept separated so that the ultimate mix batches are consistent in quality and texture. Bricks and blocks should be stacked in stable piles on a level and well-drained surface in a position where double handling is introduced to a minimum. Roof tiles have a greater resistance to load when it is imposed on the edge, for this reason tiles should be stacked on edge and in pairs, head to tail, to give protection to the nibs. Drainage goods, like tiles maybe stored in an open compound: they should be stackled with their barrels horizontal and laid with spigot and socket alternately reversed or placed in layers with the spigots and sockets reversed in alternate layers. Timber is hygroscopic material and therefore to prevent undue moisture movement it should be stored in such a manner that is moisture content remains fairly constant. Ironmongery, hand tools and paint are some of the most vulnerable items on a building site.

When mechanically moving materials, avoid overloading the equipment by letting the weight, size, and shape of the material being moved dictate the type of equipment used for transporting it. All materials handling equipment has rated capacities that determine the maximum weight the equipment can safely handle and the conditions under which it can handle those weights. The equipment-rated capacities must be displayed on each piece of equipment and must not be exceeded except for load testing. When picking up items with a

powered industrial truck, the load must be centered on the forks and as close to the mast as possible to minimize the potential for the truck tipping or the load falling. A lift truck must never be overloaded because it would be hard to control and could easily tip over. Extra weight must not be placed on the rear of a counterbalanced forklift to offset an overload. The load must be at the lowest position for traveling, and the truck manufacturer's operational requirements must be followed. All stacked loads must be correctly piled and cross-tiered, where possible. Precautions also should be taken when stacking and storing material. Stored materials must not create a hazard. Storage areas must be kept free from accumulated materials that may cause tripping, fires, or explosions, or that may contribute to the harboring of rats and other pests. When stacking and piling materials, it is important to be aware of such factors as the materials' height and weight, how accessible the stored materials are to the user, and the condition of the containers where the materials are being stored. All bound material should be stacked, placed on racks, blocked, interlocked, or otherwise secured to prevent it from sliding, falling, or collapsing. A load greater than that approved by a building official may not be placed on any floor of a building or other structure. Where applicable, load limits approved by the building inspector should be conspicuously posted in all storage areas. When stacking materials, height limitations should be observed. For example, lumber must be stacked no more than 16 feet high if it is handled manually; 20 feet is the maximum stacking height if a forklift is used. For quick reference, walls or posts may be painted with stripes to indicate maximum stacking heights. Used lumber must have all nails removed before stacking. Lumber must be stacked and leveled on solidly supported bracing. The stacks must be stable and self-supporting. Stacks of loose bricks should not be more than 7 feet in height. When these stacks reach a height of 4 feet, they should be tapered back 2 inches for every foot of height above the 4-foot level. When masonry blocks are stacked higher than 6 feet, the stacks should be tapered back one-half block for each tier above the 6-foot level.Bags and bundles must be stacked in interlocking rows to remain secure. Bagged material must be stacked by stepping back the layers and cross-keying the bags at least every ten layers. To remove bags from the stack, start from the top row first. Baled paper and rags stored inside a building must not be closer than 18 inches to the walls, partitions, or sprinkler heads. Boxed materials must be banded or held in place using cross-ties or shrink plastic fiber. Drums, barrels, and kegs must be stacked symmetrically. If stored on their sides, the bottom tiers must be blocked to keep them from rolling. When stacked on end, put planks, sheets of plywood damage, or pallets between each tier to make a firm, flat, stacking surface. When stacking materials two or more tiers high, the bottom tier must be chocked on each side to prevent shifting in either direction. When stacking, consider the need for availability of the material. Material that cannot be stacked due to size, shape, or fragility can be safety stored on shelves or in bins. Structural steel, bar stock, poles, and other cylindrical materials, unless in racks, must be stacked and blocked to prevent spreading or tilting. Pipes and bars should not be stored in racks that face main aisles; this could create a hazard to passers-by when supplies are being removed.

SECURITY AND PROTECTION

Fencing

Builders, including Owner Builders and Contractors, have a duty of care under the Occupational Health and Safety Act 1989 (the Act) to protect the public as well as workers from hazards associated with the building work. (Maximum penalty $1,000,000 or 7 years jail, or both.)

The builder or person responsible for the worksite must ensure that all hazards are identified, and risks are assessed and controlled during each stage of building work. A fence should be erected before building activities start, particularly if the site is located near a school or in a residential area, and is unattended outside work hours. A fence should be erected before building activities start, particularly if the site is located near a school or in a residential area, and is unattended outside work hours.The fence fulfils two functions:

1. Defines the limit of the site or compound2. Acts as a different to the would-be trespasser or thief

A perimeter fence can prevent unauthorised persons gaining access to the site, where they could be exposed to hazards such as building debris, exposed steel reinforcing, trenching and excavations. The main group of people exposed to hazards on building sites during non-work hours are children and adolescents.

A fence will not always stop those who are determined to gain access to a site, i.e.vandals or thieves, however it will discourage most people and may demonstrate that youhave taken reasonably practicable steps to meet your responsibilities under the Act.

HoardingsThese are closed boarded fences or barriers erevted adjacent to a high way or public

footpath to prevent unauthorized persons obtaining access to the site and to provide a degree of protection for the public from the dust and noise associated with building operations.

Two forms of hoarding are in common used:1. Vertical hoardings2. Fan hoardings

a. Hoarding of 2 meters height and continuous down to the ground, made of 12 mm sheet ply or sheet metal 0.5 mm thick, with timber or steel vertical and horizontal structural members, and including hinged lockable gates that open inwards.

b. Hoarding/fencing of 1.8 meters height and continuous down to the ground made of 50mm chain wire mesh 2.5 mm thick and including hinged lockable gates that open inwards. The support structures should enable it to withstand any foreseeable loads or impacts that could be imposed.

c. Hoarding/fencing of 1.5 meters height consisting of chain wire mesh panels, or fencing with top and bottom strainer wires, and supported by star pickets at maximum 3 meters centers. Maximum 150mm clearance from ground if materials cannot protrude. Provision to secure the site with material providing the same security as the fence at all access points.

d. Hoarding/fencing of 1.5 meters height. Maximum 150mm clearance from ground if no protruding materials risk. Must be able to withstand reasonable side forces and remain upright. For example, chain wire mesh supported by star pickets at a

maximum spacing of meters, or panel fencing with star pickets at a spacing consistent with panel width.

e. Barricades of 900mm height with horizontal guardrails from the ground, which can withstand reasonable side forces and remain upright. A plastic safety mesh barrier attached to star pickets is an acceptable alternative.

f. Visual barricade, such as orange plastic mesh, of greater than 900mm height with bottom of barricade no more than 150mm from ground. Should be installed at least 1 meters from excavations up to 2 meters deep, or from potentially unstable ground for deeper excavations. Where a person is likely to fall 1.8metres or more, edge protection must consist of a handrail at 900mm height, a mid rail, a toe board and stanchions.

CHAPTER 1.3

SUBSOIL DRAINAGE

Subsoil drainage systems are used in architectural, sewage and irrigation applications to remove excessive water from the soil surrounding a building, provide water to crops or drain sewage away from a building. Subsoil drainage systems are governed by necessary restrictions dependent on the intended purpose of the system.

The ideal site will not require any treatment but sites with a high level water table will require some from of subsoil drainage. The water table is the level at which water occurs naturally below the ground and this level will vary with the seasonal. So, as according to climate in Indonesia that tropical, in building that has a high water table must made drainage system. So, when rain, superlative water can be throw away or kept for plants irrigation

The object of subsoil drainage is to lower the water table to a level such that it will comply with the above building regulation, i.e. not rise to within 0,25m of the lowest floor of the building. So, it also has the advantage of improving its horticultural properties.

MATERIALS

The pipe used in subsoil drainage are usually dry jointed and are either porous or perforated pipes. The pipe used in subsoil drainage are usually dry jointed and are either porous or perforated pipes. Because, the porous pipes can absorb the water through walls and thus keep out the fine of soil or silt, whereas perforated pipes, which are laid with the perforations at the base, allow the water to rise into the pipe leaving any silt behind.

Size, Shape and Material Specifications

In most applications, the specifications on size and shape of subsoil drainage systems are similar. Most applications, such as simple water drainage for home placement and sewage uses, require shaped drainage pipes circular pipes. Also, to prevent excessive clogging, the drainage pipes are required to be 3 inches or more in diameter. The pipes can be made of clay, cement or plastic; this is dependent upon the intended use.

Geographical Placement

Placement of the drainage system is dependent upon many factors including: use, delivery of drained substance and surrounding subsoil features. For many applications, regulations specify that the drainage system must have a specific surrounding zone in which there may not be any other types of piping. For example, in the sewage application, the subsoil drainage system, also known as a leach bed system, must have an 8-foot bunker where no other piping, such as a water line or electrical line, may pass.

Options and Variations

Specifications on placement and types of subsoil drainage systems vary from place to place. Although suburban drainage systems must empty into a sewer or larger city-owner

drainage system, rural residents may drain their sewage subsoil system into the ground and their water waste and groundwater into nearby streams. In rural areas, drainage systems for water do not have to be constructed of pipes but may also be in the form of trenches filled with gravel.

Warnings and Preventions

Problems with subsoil drainage systems can arise--and are usually costly to repair--so proper installation is a necessity. Having drainage system technicians install the piping may be expensive, but their expertise will prevent you from spending extra money later to repair your system. Before attempting the project yourself, consult a drainage specialist to give you the specifications and advice on installing your drainage system properly.

DRAINAGE LAYOUTS

The pipes are arranged in pattern to cover as much of the site as is necessary. Water will naturally flow towards the easy passage provided by the drainage runs. The system is terminated at a suitable outfall such as a river. The banks of streams and river will need protection against the turbulence set up by the discharge and if the stream is narrow the opposite bank may also protection. One large schemes sediment chambers or catch pits are sometimes included to trap some of the silt which is the chief cause of blockages in subsoil drainage work. The collected silt in the catch pit must be removed at regular intervals.

CHAPTER 1.4

EXCAVATIONS AND TIMBERING

Excavation is removal of earth to form a cavity in the ground. Before the foundation can be laid it is necessary to excavate a trench of the required depth and width. On small project like build a house better done by hand, but on large project it will be more economic and must be done with mechanical excavator.

When earth has been excavated to a considerable depth the vertical faces of the excavations need supporting by timber, to prevent the soil from falling in the injuring the workmen or the work upon which there are engaged.

The strength of the timbering used for this purpose necessarily depends upon the nature of the soil, the depth of the excavation, and the length of time it is likely to be kept open.

When excavated as deep as possible without the earth falling in. Vertical sheeting from 9 by 1 inch to 9 by 2 1/2 inches, according to the nature of the soil, is temporally strutted against the faces of the excavation.

TYPES OF EXCAVATION:

1. Over siteo the removal of top soilo depth varies from site to site (usually in a 150 to 300 mm range)o required since top soil often contains plant life, animal life and decaying matters making

soil compressible and thus unstable for supporting building

2. Reduce Level (R. L.)o required in irregular sites to form a level surfaceo consists of both cutting and filling operationso the level to which the ground is reduced is called the formation level

3. Trench Excavationo excavation of trench of required depth and width before laying out foundationo done both manually (with use of spade, pick axe, rammer, etc. and for small buildings)

and mechanically (with use of bulldozers, trench diggers, etc. and for large buildings)

Typical examples of trench excavation

i. Battered / Sloped face excavationAdvantage: no temporary support required to the sides of excavation

Disadvantage: extra cost and time required for over excavation and back filling

ii. Vertical / Straight face excavationAdvantage: only required amount of soil is removed and thus min. amount of back filling

Disadvantage: side of excavation require some degree of temporary support

Problems in deep excavation (excavation beyond 1.5m deep is deep excavation):

collapsing of the sides of trenches water coming out of the sides or bottom of the excavation

Dewatering

o ground water can cause problem by its natural tendency to flow into the voids created by excavation

o water in excavation should be removed since it can : o undermine sides of excavationo make it impossible to adequately compact the bottom of excavation to receive

foundationo bearing capacity of the soil is reduced with water stored in voids of the bottom of

excavation

FAILURE OF TIMBERING

Serious accidents happen from time to time owing to the failure of timbering in excavations. This failure is usually due to one of the following two reasons:

1. The struts fail under the pressure of the earth; or,

2. The struts drop out by the shrinkage of the soil.

This is perhaps the most frequent cause of failure, as the pressure from soils is often underestimated, particularly that of clay soils, which sometimes swell when exposed to the atmosphere. When excavations are made in soft soil in around of heavy buildings the lateral pressure of the soil is usually very great.

To prevent such failures the timber should be of ample size, and should be examined before being inserted in the excavations, while in very deep trenches the struts in the lower parts of the trenches should be larger than those near the surface.

To prevent struts dropping out of place they should be examined from time to time and tightened when necessary; but a better plan is to spike them to the walings. The struts supporting stages should always be spiked or fixed in some way, as they are very likely to become loosened by the weight and motion of the excavator, who stands upon them to work.

TIMBERING

This is a term used to cover temporary supports to the side of excavations and is sometimes called planking and strutting. The sides of some excavations will need support to:

Protect the operatives while working in the excavation. Keep the excavation open by acting as a retaining wall to the side of the trench.

The type and amount of timbering required will depend upon the depth and nature of the subsoil. Over a short period many soils may not required any timbering but weather conditions, depth, type of soil and duration of the operations must all be taken into account and each excavation must be assessed separately.

METHODS OF TIMBERING

o methods depend upon the nature of the soilo timbering is defined as providing temporary timber supports to stop the sides of trenches

from falling

1. Stay Bracing o open timberingo for firm / stiff / rocky hard soilo for excavation not exceeding about 2m in deptho consists of placing vertical sheets called polling boards, opposite to each other against the

walls and holding them in position by one or two rows of strutso polling boards are placed at an interval of 2 – 4m and extend to full height of trencho polling board : 200 x 40 – 50 mm., struts : 100 x 100 mm for up to 2m wide excavation

and 200 x 200 mm for up to 4m wide excavation

2. Box Sheeting o closed timbering, box like structureo two types of box sheeting : Vertical Sheeting and Horizontal SheetingVertical Sheeting

o for loose / loamy / dry sandy soilo for depth of excavation not exceeding 4mo consists of vertical sheets placed very near to each other / touching each other

and keeping them in position by longitudinal rows (usually two) of waleso struts are then provided across the wales

Vertical sheeting for deep trencheso for up to 10m deep trencheso for soft groundo excavation is carried out in stages and at the end of each stage offset is

provided so that the width of the trench goes on decreasing as the depth increases

o each stage is 3m in deptho offset : 25 – 30 cm per stageo separate vertical sheeting for each stage supported by horizontal wales and

struts

Horizontal Sheeting

o for loose soilo horizontal sheets are provided longitudinally and supported by vertical waling

and horizontal strutso if height is more, braces are also provided along with struts

3. Runner System o closed timberingo for extremely loose, soft and wet soilo for soil needing immediate support after excavationo similar to vertical system except for, runners are provided in place of vertical sheetso runners with iron shoes at the endo runners are driven 30 cm in advance by hammeringo wales and struts are provided as in vertical sheeting

CHAPTER 1.5

SCAFFOLDING

Scaffolding is a temporary platform constructed for reaching heights above arms' reach for the purpose of building construction, maintenance, or repair. Scaffolding is generally made of lumber and steel and can range from simple to complex in design, depending on its use and purpose. Scaffold planking must be able to support, without failure, its own weight and at least four times the intended load. Solid sawn wood, fabricated planks, and fabricated platforms may be used as scaffold planks following the recommendations by the manufacturer or a lumber grading association or inspection agency. The platform must not deflect more than 1/60 of the span when loaded.

Basically there are two forms of scaffolding:

1. Putlog scaffolds.

2. Independent scaffolds.

Putlog Scaffolds

This forms of scaffolding consist of a single row of uprights or standards set away from the wall at a distance which will accommodate the required width of the working platform. The standards are joined together with horizontal members called ledgers and are tied to the building with cross called putlogs.

Independent Scaffolds

An independent scaffold has two rows of standards which are tied by cross members called transoms. Every scaffold should be securely tied to the building at intervals of approximately 3.600 m vertically and 6.000 m horizontally. This can be achieved by using a horizontal tube called a bridle bearing on the inside of the wall and across a window opening with cross members connected to it; alternatively a tube with a reveal pin in the opening can provide a connection point for the cost members. If suitable openings are not available then the scaffold should be strutted from the ground using raking tubes inclined towards of building

MATERIALS

Tubular steel

Steel tubes are nearly three times heavier than comparable aluminium alloy tubes but are far stronger and since their deflection is approximately one-third of aluminium alloy tubes, longer span can be used.

Tubular alluminium alloy

No protective treatment is required unless they are to be used in contact with materials such as damp lime, wet cement, and sea water, which can cause corrosion of the aluminium alloy tubes. A suitable protective treatment would be to coat the tubes with bitumastic paint before use.

Timber

The timber used is structural quality softwood in either putlog or independent format. The members are lashed together with wire or rope instead of the coupling fitting used with metal scaffolds.

SCAFFOLD BOARDS

They should be formed out of specified softwoods of 225 x 38 section and not exceeding 4.800 m in length. To prevent the ends from splitting they should be end bound with not less than 25 mm wide x 0.9 mm galvanized hoop iron extending at least 150 mm along each edge and fixed with a minimum of two fixings to each end. The strength of the boards should be such that they can support a uniformly distributed load of 6.7 kN/m2 when supported at 1.200 m centers.

Each scaffold platform and walkway must be at least 18 inches (46 centimeters) wide. When the work area is less than 18 inches (46 centimeters) wide, guardrails and/or personal fall arrest systems must be used.

SCAFFOLD FITTINGS

Fittings of either steel or aluminium alloy are covered by the same British Standard as quoted above for the tubes. They can usually be used in conjunction with either tubular metal unless specified differently by the manufacturer. The major fittings used in metal scaffolding are:

Double coupler: the only real load bearing fitting used in scaffolding and is used to join ledgers to standards.

Swivel coupler: composed of two single couplers riveted together so that it is possible to rotate them for connecting two scaffold tubes at any angle.

Putlog coupler: used softly for fixing putlogs or transoms to the horizontal ledgers.

Base plate: a square plate with a central locating spigot used to distribute the load from the foot of a standard on to a sole plate or firm ground. Base plates can also be obtained with a threaded spigot and nut for use on sloping to make up variations in levels.

Split joint pin: a connection fitting used to joint scaffold tubes end to end. A centre bold expands the two segments which grip on the bore of the tubes.

Reveal pin: fits into the end of a tube to form and adjustable strut.

Putlog end: a flat plate which fits on the end of a scaffold tube to convert it into a putlog

Millions of construction workers, painters, and building maintenance crews work on scaffolding every day, and due to the nature of its use, scaffolding must be properly constructed and used to ensure the safety of those who use it. The US Department of Labor Occupational Safety and Health Organization (OSHA) has very specific standards for the construction and use of scaffolding in the workplace, and many large commercial and government construction projects require all workers to have scaffold training and OSHA certification. Some of OSHA's regulations regarding construction of scaffolding include using specific types of lumber when not using steel, weight limitations based on the design of the scaffolding, and regular checks for weakened or broken sections. OSHA places stringent safety regulations on the construction and use of scaffolding not only to reduce serious workplace injury or death, but also to save employers millions in lost time and workers' compensation OSHA can issue fines to any company, large or small, that they find to be in violation of scaffolding regulations. Commercial construction accounts for the largest use of scaffolding, but even residential construction and home improvement projects can sometimes require scaffolding. Professional painters are equipped to quickly and properly construct scaffolding on the job, as are other professionals such as bricklayers and carpenters. Unfortunately, many homeowners attempt to construct scaffolding for personal use without the proper knowledge, which often results in injury. To avoid personal injury when attempting to repair, paint, or maintain your home, be sure you know how to properly and safely erect a scaffolding platform that will provide a stable work surface and will bear the weight you place on it. If you are unsure how to construct or use scaffolding, consult a professional contractor.

OSHA's scaffolding standard has several key provisions:

Fall protection or fall arrest systems -- Each employee more than 10 feet above a lower level shall be protected from falls by guardrails or a fall arrest system, except those on single-point and two-point adjustable suspension scaffolds. Each employee on a single-point and two-point adjustable suspended scaffold shall be protected by both a personal fall arrest system and a guardrail.

Guardrail height -- The height of the top rail for scaffolds manufactured and placed in service after January 1, 2000 must be between 38 inches (0.9 meters) and 45 inches (1.2 meters). The height of the top rail for scaffolds manufactured and placed in service before January 1, 2000 can be between 36 inches (0.9 meters) and 45 inches (1.2 meters).

Cross bracing -- When the cross point of cross bracing is used as a top rail, it must be between 38 inches (0.97 m) and 48 inches (1.3 meters) above the work platform.

Mid rails – Mid rails must be installed approximately halfway between the top rail and the platform surface. When a cross point of cross bracing is used as a mid rail, it must be between 20 inches (0.5 meters) and 30 inches (0.8 m) above the work platform.

Footings -- Support scaffold footings shall be level and capable of supporting the loaded scaffold. The legs, poles, frames, and uprights shall bear on base plates and mud sills.

Platforms -- Supported scaffold platforms shall be fully planked or decked.

Guying ties, and braces -- Supported scaffolds with a height-to-base of more than 4:1 shall be restained from tipping by guying, tying, bracing, or the equivalent.

Capacity -- Scaffolds and scaffold compponents must support at least 4 times the maximum intended load. Suspension scaffold rigging must at least 6 times the intended load.

Training -- Employers must train each employee who works on a scaffold on the hazards and the procedures to control the hazards.

Inspections -- Before each work shift and after any occurrence that could affect the structural integrity, a competent person must inspect the scaffold and scaffold components for visible defects.

Erecting and Dismantling -- When erecting and dismantling supported scaffolds, a competent person must determine the feasibility of providing a safe means of access and fall protection for these operations.

Kind of fall protection to provide for a specific-type of scaffold

The chart on the next page illustrates the type of fall protection required for specific scaffolds.

Type of Scaffold Fall Protection Required

Aerial lifts Personal fall arrest system

Boatswains' chair Personal fall arrest system

Catenary scaffold Personal fall arrest system

Crawling board (chicken ladder) Personal fall arrest system, or a guardrail system, or by a 3/4 inch (1.9 cm) diameter grab line or equivalent handhold securely fastened beside each crawling board

Float scaffold Personal fall arrest system

Ladder jack scaffold Personal fall arrest system

Needle beam scaffold Personal fall arrest system

Self-contained scaffold Both a personal adjustable scaffold arrest system and a guardrail system

Single-point and two-point suspension scaffolds

Both a personal fall arrest system and a guardrail system

Supported scaffold Personal fall arrest system or guardrail system

All other scaffolds not specified above

Personal fall arrest system or guardrail systems that meet the required criteria

SUBSTRUCTURE

CHAPTER 2.1

TRENCH AND BESEMENT EXCAVATION

TRENCING AND EXCAVATION SAFETY

Safety requirements in subsurface excavation, including basement, are strictly enforced through the construction. Material must not be placed near the edge of any excavation, so that persons working in the excavation are endangered.

Excavation and trenching are among the most hazardous construction operations. OSHA defines an excavation as any man-made cut, cavity, trench, or depression in the earth’s surface formed by earth removal. A trench is defined as a narrow underground excavation that is deeper than it is wide, and is no wider than 15 feet (4.5 meters).

Dangers of Trenching and ExcavationCave-ins pose the greatest risk and are much more likely than other excavation related accidents to result in worker fatalities. Other potential hazards include falls, falling loads, hazardous atmospheres, and incidents involving mobile equipment. Trench collapses cause dozens of fatalities and hundreds of injuries each year. Protect YourselfDo not enter an unprotected trench! Trenches 5 feet (1.5 meters) deep or greater require a protective system unless the excavation is made entirely in stable rock. Trenches 20 feet (6.1 meters) deep or greater require that the protective system be de-signed by a registered professional engineer or be based on tabulated data prepared and/ or approved by a registered professional engineer.Protective SystemsThere are different types of protective systems. Sloping involves cutting back the trench wall at an angle inclined away from the excavation. Shoring requires installing aluminum hydraulic or other types of supports to prevent soil movement and caveins. Shielding protects workers by using trench boxes or other types of supports to prevent soil cave-ins. Designing a protective system can be complex because you must consider many factors: soil classification, depth of cut, water content of soil, changes due to weather or climate, surcharge loads (eg, spoil, other materials to be used in the trench) and other operations in the vicinity.

Competent PersonOSHA standards require that trenches be inspected daily and as conditions change by a competent person prior to worker entry to ensure elimination of excavation hazards. A competent person is an individual who is capable of identifying existing and predictable hazards or working conditions that are hazardous, unsanitary, or dangerous to employees and who is authorized to take prompt corrective measures to eliminate or control these hazards and conditions.

Access and EgressOSHA requires safe access and egress to all excavations, including ladders, steps, ramps, or other safe means of exit for employees working in trench excavations 4 feet (1.22 meters) or deeper. These devices must be located within 25 feet (7.6 meters) of all workers.

1. General Trenching and Excavation Rules

2. Keep heavy equipment away from trench edges.

3. Keep surcharge loads at least 2 feet (0.6 meters) from trench edges.

4. Know where underground utilities are located.

5. Test for low oxygen, hazardous fumes and toxic gases.

6. Inspect trenches at the start of each shift.

7. Inspect trenches following a rainstorm.

8. Do not work under raised loads.

TRENCH EXCAVATION

Long narrow trenches in firm soil may be excavated to the full depth by mechanical excavator. In the latter method the runners can be driven to a reasonable depth of approximately 1.500 m followed by an excavation cut of 1.200 m and then the operation easier and enable a smaller driving appliance to be used.

In medium depth trenches different soil conditions are very often encountered trough out the depth of the excavation and therefore the method of timbering must be changed to suit the new soil conditions.

Hand trimming is usually required in the trench bottom to form an accurate line and level; this process is called bottoming of trenches. Approximately 5 mm should be allowed for trimming by hand and it is advisable to cover the trimmed surface with hard core to protect the soil.

Trench excavation shall consist of the removal and satisfactory disposal of all materials, the removal of which is necessary for the proper completion of the work, to the dimensions shown on the plans or as ordered, and backfilling, all in accordance with these specifications for the following:

1. The construction of pipe culverts, end walls, catch basins, drop inlets, manholes, under drains and outlets, sewers, service pipes,

2. The removal of drainage structures and appurtenances beyond the limits of roadway and structure excavation,

3. The removal of miscellaneous items such as abandoned underground tanks, pipelines, etc.

Trench excavation will be allowed only for the construction of the structures and the removals definitely specified above; and no compensation will be made for any other class of excavation, as specified elsewhere herein, that may be necessary for construction or removal.

Trench excavation shall be made in conformity with the requirements of the plans or as ordered. The Contractor shall furnish and employ such shores, braces, pumps, etc., as may be necessary for the protection of property, proper completion of the work and the safety of the public and employees of the Contractor and the Department. All bracing, etc., shall be removed when no longer required for the construction or safety of the work.

For minor ditches or trenches, simply using a shovel and setting about digging is sufficient, but for excavating a deep trench, often needed for sanitary sewer installation or other projects, special consideration should be made.

Choose a route that will not damage valuable plants or appurtenances on the property. Trees, shrubs and other plants may suffer injury or die if their roots are damaged in excavation. Driveways, sidewalks, and structures can collapse if they are undermined.

Determine the type of soil which will be digging in. Sandy soils, loose stony soils, and wet, mucky material will make excavating a straight, deep ditch difficult and dangerous.

Shoring. This process uses a support structure for ditch sides so they do not cave in and injure anyone, or undo the digging that have done before the project is complete. Examples may be sheets of plywood with posts to support them for small excavations, or steel trench boxes or sheet piling for very large ones.

Dewatering. This will remove the excess water from the soil to help stabilize it while working. This can be accomplished either with a well point system pipe to remove the water as it seeps into the excavation.

Benching the excavation. This is the technique for dealing with loose soils illustrated in this article. As the trench is excavated, the sides step down so the banks do not have to support more material than they are capable of.

Determine the depth the utility or other function of trench will require. Some plumbing systems are gravity operated, and require a slope so the waste or water will flow unaided to the discharge location in this situation.

Call the local or government utility location service so that underground gas, electric, water, and communications pipes and cables can be spotted, to protect worker from injury or liability in the event they are damaged.

Remove any vegetation will want to save and replace when the project is finished. Small plants, even turf grasses, can be removed and stored for replanting with proper care.

Remove the topsoil to a depth of 10-20cm, depending on depth of the topsoil layer. Store the topsoil away from other spoil material to avoid contamination. Ensure that the topsoil heap does not exceed 1 - 1.5m in height to avoid compaction. For the same reason the topsoil heap should either be demarcated or placed away from frequent foot or vehicular traffic if the topsoil is going to be stored for prolonged periods of time over-seed with non-invasive grass species to reduce erosion.

BASEMENT EXCAVATION

A basement excavation is a construction dig performed for the purpose of roughing out a basement. There are several settings in which basement excavation may be performed. This procedure is usually supervised by an experienced contractor or a basement excavation company, because it can be complicated in addition to labor intensive. While it is possible to excavate by hand, there are some serious risks which must be carefully evaluated before taking the plunge.

The best time to do a basement excavation is when a home site is being prepared. In this case, the site is already being excavated in preparation for laying the foundations. If people want a basement, the depth of the excavation can be deepened to rough out the basement so that the basement and foundations can be established at the same time. This can be a way to add room to a structure without adding height, and some people leave the basement unfinished to cut costs while ensuring that they will have that space available at a later time if they need it.

Once a home is already built, basement excavation can be done for a number of reasons. If a home needs foundation work, it may be necessary to excavate under the home or in the basement in order to get the work done. As long as excavation is being done, some people may opt to rough in a basement at the same time, or to make improvements to an existing basement. Another reason for a basement excavation is the desire to add a basement to an existing structure.

Excavating under a building can be tricky. The structure needs to be supported during the excavation to avoid compromise to the structural integrity which could make it unsafe. People also need to provide an area to store excavated materials, usually with the goal of

eventually hauling them away. It is also possible to encounter unexpected hazards such as mold or mildew. In older homes, people sometimes find materials of historical interest during a basement excavation because it was not uncommon to build directly on top of debris.

Specialty companies focus entirely on doing basement excavation and they can be a good choice for this type of construction project. These companies have a great deal of experience in making excavations go smoothly and they can coordinate with other companies who may be involved to make the process as efficient as possible. People should be aware that permits are generally required for a basement excavation and that a building inspector will want to visit the site to confirm that safety procedures are being followed.

There are three methods which can be used for excavating a large pit or basement:

1. Complete excavation with sloping sides

2. Complete excavation with timbered sides

3. Perimeter trench method

Excavation of a basement on an open site can be carried out by cutting the perimeter back to the natural angle of repose of the soil. This method requires sufficient site space around the intended structure for the over-excavation.

In firm soils where poling boards can be placed after excavation an economic method is to excavate the bulk of the pit and then trim the perimeter, placing the poling boards with their raking struts in position as the work proceeds.

The perimeter trench method is used where weak soils are encountered; a trench wide enough to enable the retaining walls to be constructed is excavated around the perimeter of the site and timbered according to the soil conditions. This method could be also be used in firm soil when the mechanical excavation required for bulk excavation are not available.

Chapter 2.2

FOUNDATION

Whenever construction workers begin work on a new building, they must first assess where and how they will build the foundation. The foundation is a structure, commonly made of concrete for home that transfers the weight of the building onto the earth below. There are different types of foundation designs and each serves a different specific purpose, but generally, every foundation works to transfer the weight load of a structure to the soil beneath.

Most small and medium homes are built upon a shallow foundation. These are usually comprised of concrete strips that are laid about a meter beneath the soil, or of a single large concrete slab that is also set about a meter under the soil. When applicable, the foundation will extend beneath the frost line. When engineers design the foundation of a building, they must keep in mind how much the soil will settle beneath the foundation, as well as how much weight will go on top of the foundation. If calculated incorrectly, the foundation may fail and place the entire structure in peril.

Larger buildings use a deep foundation rather than a shallow foundation. A deep foundation uses long pylons of steel or concrete to penetrate deep beyond the weaker surface soils into the deeper and more stable soils or bedrock beneath. The loads from walls above are transferred deep into the earth, thereby providing support for the intense weight above. Much like the considerations for a shallow foundation, engineers must consider weight and settlement, as well as scour -- or, water eroding soil beneath the structure.

For structures being built in colder climates, engineers must consider frost heaves as well. Frost heaves occur when moisture in the soil freezes, thereby changing the density of the foundation's support. A frost heave can cause damage to the foundation, thereby compromising the structural integrity of the entire building. Drier, warmer climates are not entirely exempt from such worries, however: certain soils will expand and contract when moisture is added or taken away, and engineers must factor in such movement when considering where and how to lay a foundation.

TYPES OF FOUNDATION

Deep Foundation

A type of foundation distinguished from shallow foundations by the depth they are embedded into the ground. There are many reasons a geotechnical engineer would recommend a deep foundation over a shallow foundation, but some of the common reasons are very large design loads, a poor soil at shallow depth, or site constraints (like property lines). There are different terms used to describe different types of deep foundations including piles, drilled shafts, caissons and piers. The naming conventions may vary between engineering disciplines and firms. Deep foundations can be made out of timber, steel,

reinforced concrete and pre-tensioned concrete. Deep foundations can be installed by either driving them into the ground or drilling a shaft and filling it with concrete, mass or reinforced.

Driven Foundations

Prefabricated piles are driven into the ground using a pile driver. Driven piles are either wood, reinforced concrete, or steel. Wooden piles are made from trunks of tall trees. Concrete piles are available in square, octagonal, and round cross-sections. They are reinforced with rebar and are often pretressed. Steel piles are either pipe piles or some sort of beam section (like an H-pile). Historically, wood piles were spliced together when the design length was too large for a single pile; today, splicing is common with steel piles, though concrete piles can be spliced with difficulty. Driving piles, as opposed to drilling shafts, is advantageous because the soil displaced by driving the piles compresses the surrounding soil, causing greater friction against the sides of the piles, thus increasing their load-bearing capacity.

Shallow Foundation

A type of foundation which transfers building loads to the earth very near the surface, rather than to a subsurface layer or a range of depths as does a deep foundation. Shallow foundations include spread footing foundations, mat-slab foundations, slab-on-grade foundations, rubble trench foundations, and earth bag foundations.

Spread Footing Foundation

In ground reinforced concrete foundation in cyclonic area, Northern Spread footing foundations consists of strips or pads of concrete (or other materials) which transfer the loads from walls and columns to the soil or bedrock. Embedment of spread footings is controlled by several factors, including development of lateral capacity, penetration of soft near-surface layers, and penetration through near-surface layers likely to change volume due to frost heave or shrink-swell.

These foundations are common in residential construction that includes a basement, and in many commercial structures.

Mat-slab foundations

Mat-slab foundations are used to distribute heavy column and wall loads across the entire building area, to lower the contact pressure compared to conventional spread footings. Mat-slab foundations can be constructed near the ground surface, or at the bottom of basements. In high-rise buildings, mat-slab foundations can be several meters thick, with extensive reinforcing to ensure relatively uniform load transfer.

Slab-on-grade foundation

Slab-on-grade foundations are a structural engineering practice whereby the concrete slab that is to serve as the foundation for the structure is formed from a mold set into the ground. The concrete is then placed into the mold, leaving no space between the ground and the structure. This type of construction is most often seen in warmer climates, where ground freezing and thawing is less of a concern and where there is no need for heat ducting underneath the floor.

The advantages of the slab technique are that it is cheap and sturdy, and is considered less vulnerable to termite infestation because there are no hollow spaces or wood channels leading from the ground to the structure (assuming wood siding, etc., is not carried all the way to the ground on the outer walls).

The disadvantages are the lack of access from below for utility lines, the potential for large heat losses where ground temperatures fall significantly below the interior temperature, and a very low elevation that exposes the building to flood damage in even moderate rains. Remodeling or extending such a structure may also be more difficult. Over the long term, ground settling (or subsidence) may be a problem, as a slab foundation cannot be readily jacked up to compensate; proper soil compaction prior to pour can minimize this. The slab can be decoupled from ground temperatures by insulation, with the concrete poured directly over insulation (for example, Styrofoam panels), or heating provisions (such as hydronic heating) can be built into the slab (an expensive installation, with associated running expenses).

Slab-on-grade foundations are commonly used in areas with expansive clay soil, particularly in California and Texas. While elevated structural slabs actually perform better on expansive clays, it is generally accepted by the engineering community that slab-on-grade foundations offer the greatest cost-to-performance ratio for tract homes. Elevated structural slabs are generally only found on custom homes or homes with basements.

Care must be taken with the provision of services through the slab. Copper piping, commonly used to carry natural gas and water, reacts with concrete over a long period, slowly degrading until the pipe fails. Copper pipes must be lagged (that is, insulated) or run through a conduit or plumbed into the building above the slab. Electrical conduits through the slab need to be water-tight, as they extend below ground level and can potentially expose the wiring to groundwater.

Rubble Trench foundation

The rubble trench foundation, a construction approach popularized by architect Frank Lloyd Wright, is a type of foundation that uses loose stone or rubble to minimize the use of concrete and improve drainage. It is considered more environmentally friendly than other types of foundation because cement manufacturing requires the use of enormous amounts of energy. However, some soil environments (such as particularly expansive or poor load-bearing (< 1 ton/sf) soils) are not suitable for this kind of foundation.

A foundation must bear the structural loads imposed upon it and allow proper drainage of ground water to prevent expansion or weakening of soils and frost heaving.

While the far more common concrete foundation requires separate measures to ensure good soil drainage, the rubble trench foundation serves both foundation functions at once.

To construct a rubble trench foundation a narrow trench is dug down below the frost line. The bottom of the trench would ideally be gently sloped to an outlet. Drainage tile, graded 1":8' to daylight, is then placed at the bottom of the trench in a bed of washed stone protected by filter fabric. The trench is then filled with either screened stone (typically 1-1/2") or recycled rubble. A steel-reinforced concrete grade beam is poured at the surface to provide ground clearance for the structure.

aIf an insulated slab is to be poured inside the grade beam, then the outer surface of the grade beam and the rubble trench should be insulated with rigid XPS foam board, which must be protected above grade from mechanical and UV degradation.

The rubble-trench foundation is a relatively simple, low-cost, and environmentally-friendly alternative to a conventional foundation, but may require an engineer's approval if building officials is not familiar with it. Frank Lloyd Wright used them successfully for more than 50 years in the first half of the 20th century, and there is a revival of this style of foundation with the increased interest in green building.

Earth bag foundation

The basic construction method begins by digging a trench down to undisturbed mineral subsoil. Rows of woven bags (or tubes) are filled with available material, placed into this trench, compacted with a pounder to around 1/3 thickness of pre-pounded thickness, and form a foundation. Each successive layer will have one or more strands of barbed wire placed on top. This digs into the bags weave and prevents slippage of subsequent layers, and also resists any tendency for the outward expansion of walls. The next row of bags is offset by half a bag's width to form a staggered pattern. These are either pre-filled with material and delivered, or filled in place (often the case with Super adobe). The weight of this earth-filled bag pushes down on the barbed wire strands, locking the bag in place on the row below. The same process continues layer upon layer, forming walls. A roof can be formed by gradually slope the walls inward to construct a dome. Traditional types of roof can also be made.

By far the most common structural foundation in today's construction industry is the shallow foundation. Other types of foundations, such as piles, piers, caissons, and similar deep foundations, are used primarily for major structures, not for ordinary building that constitute the overwhelming majority of all constructions.

1. ADVANTAGES OF USING SHALLOW FOUNDATION Cost (affordable)

Construction Procedure (simple)

Materials (mostly concrete)

Labor (does not need expertise)

2. DISADVANTAGES OF USING SHALLOW FOUNDATION

Settlement

Limit Capacity * Soil * Structure

Irregular ground surface (slope, retaining wall)

Foundation subjected to pullout, torsion, moment.