Tech Drawing Project

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FEDERAL GOVERNMENT ACADEMY

NIGER STATE

TECHNICAL DRAWING PROJECT

STAGES INVOLVED IN BUILDINGA HOUSE FROM

FOUNDATION TO ROOF LEVEL

BY

ANYAOKU NKEM

OF

SS3B


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SEPTEMBER 2010

TABLEOF CONTENTS

ACKNOWLEDGEMENT

INTRODUCTION

STEPS TO BUILDING A HOUSE

SITE PREPARATION

FOUNDATION

BASEMENT

CRAWL SPACE

FLOOR


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WALLS

ROOFING

THE ARCHITECT WORK

ACKNOLEDGEMENTThis project required a lot of research and continuous

work which was made possible by the assistance of my

family and friends from various works of life and God

Almighty.

These group of people where there for me in my

academic, financial and moral needs and most of all sawto the completion of this project, to them all I owe my

gratitude. Thank you all.


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INTRODUCTION

This project concerns the various steps in the buildingand construction of a house from foundation to roof level.

It portrays the numerous ideas and facts considered by

those involved in house building, how a building plan of a

house should look like, the various steps in each stage of

construction and how a finished house should look using

a 3 bedroom flat as a case study.

The relevance of all this is to show that not only a good

foundation makes a house but also the walls, doors etc.

Non professional site engineers do not abide by this

leading to the collapse of their houses.


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Steps to Building a HouseOne of the amazing things about Western homes is thatthe huge majority of them are built using completelystandardized building practices. One reason for thisconsistency is a set of uniform building codes that applyacross the country. Another reason is cost -- thetechniques used to build homes produce reliable housingquickly at a low cost (relatively speaking). If you ever

watch any house being built, you will find that it goesthrough the following steps:

Grading and site preparation Foundation construction Framing Installation of windows and doors Roofing Siding Rough electrical Rough plumbing Rough HVAC Insulation Drywall Underlayment
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Trim Painting Finish electrical Bathroom and kitchen counters and

cabinets Finish plumbing Carpet and flooring Finish HVAC Hookup to water main, or well drilling Hookup to sewer or installation of aseptic system Punch list

Many of these steps are performed by independent crewsknown as subcontractors. For example, the framing isgenerally done by one subcontractor specializing inframing, while the roofing is done by a completelydifferent subcontractor specializing in roofing. Eachsubcontractor is an independent business. All of thesubcontractors are coordinated by a contractor whooversees the job and is responsible for completing the

house on time and on budget.We will walk through these different stages so that youcan see what is involved, understand all the steps andlearn about the different materials used in theconstruction process. We will use a typical three-bedroomhome as our example.

Site PreparationThe first crew on the site handles site preparation. Often,this crew and the foundation crew are the same people,but sometimes not (especially if there are a lotoftrees on the lot). Houses are generally built on a
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foundation that is either a basement, a crawl space ora slab. The site-preparation crew typically arrives on thesite with a backhoe and/or bulldozer. The crew's job is toclear the site of any trees, rocks and debris, level the site

if necessary and dig as necessary for the foundationbeing built.

For a crawl space, the site preparation crew digs a set oftrenches and holes. Concrete is poured into thesetrenches and holes and will act as the interface betweenthe foundation wall and the ground. Once the concrete is

poured, the house looks like this:

(In these pictures, the bricks for the crawl space havealready been moved into position while the concretecures.) The concrete in the trench is generally about 18to 24 inches wide (45.72 to 60.96 cm) and 18 to 24inches deep. Once it hardens, it forms a massive concrete"beam" on which the house rests. The width of
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this concrete beam is controlled by the compressibilityof the soil. In light soils, the beam will be wider to try tospread out the load, while in heavy clay soils it can benarrower.

If the site slopes, the concrete beam is stepped, like this:

Concrete takes approximately four weeks to cure to full

strength (depending on the weather), so once theconcrete is poured nothing will happen for some period oftime while the initial curing takes place.

If this house had been built on a basement, the site-prepcrew would have dug a square hole about 8 feet deep. Ifthis house had been built on a slab, the site-prep crewwould have trenched around the outside approximately 2feet deep and then completely leveled the area for the

pad.

Foundation


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Slabs, basements and crawl spaces are the three mainfoundation systems used on houses. In wet and coastalareas, it is sometimes common to put houses up on postsas well.

Slab

The slab is probably the easiest foundation to build. It is

a flatconcrete pad poured directly on the ground. It takesvery little site preparation, very little formwork for theconcrete and very little labor to create. It works well onlevel sites in warmer climates -- it has problems up northbecause the ground freezes in the winter and thisfreezing can shift the slab at worst and at least lead tocold floors in the winter. A cross-section of a typical slablooks like this.Around the edge of the slab, the concrete forms a beamthat is perhaps 2 feet deep. The rest of the slab is 4 or 6inches thick. A 4- or 6-inch layer of gravel lies beneaththe slab. A 4-millimeter sheet of plastic lies between theconcrete and the gravel to keep moisture out. Embeddedin the concrete is 6-inch by 6-inch wire mesh (shown by
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the dotted line in the slab) and steel reinforcing bars(shown by the white circles at the bottom of the beams).

You will often hear this sort of foundation referred to as a"floating slab" -- it "floats" on the soil, with the deeper

concrete around the edge holding it in place. In northernclimates, the concrete around the edge has to extenddeep enough to remain below the frost line in winter.One thing about a slab is that the sewer pipe, andsometimes much of the electrical conduit, has to be putin place before the concrete is poured. The sewer pipesare actually embedded in the slab.

Basement

A house with a basement starts with a hole about 8 feetdeep. At the bottom of the hole is a concrete slab, andthen concrete or cinder-block walls form the outer wallsof the basement. Actually, a basement is poured in threepieces in most cases: the "beams," then the walls, andthen the slab inside the walls, like this.
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This approach helps keep the basement waterproof. TheL-shaped piece is a steel reinforcing bar to bind the beamand the wall together.

Crawl Space

A crawl space has several advantages over basementsand slabs:

It gets the house up off the ground (especiallyimportant in damp ortermite-prone areas). It is a lot less expensive than a basement andcomparable in price to a slab. Duct work and plumbing can run in the crawlspace, meaning that they are easy to service andmove over the lifetime of the house.

Most of the time, a crawl space is made ofcinder blockwith a brick facing.

This is exactly how our sample house is put together.You might have noticed in the previous pictures that the

concrete work for the crawl space was not done withmuch precision at all. One of the neat things thatthe mason (bricklayer) does is carefully adjust the heightof the cinder blocks and bricks with mortar thickness sothat the crawl-space walls end up exactly level all theway around.
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One problem that arises in crawl spaces and basementsis dampness. In order to keep water out, perforated pipeand gravel are used in a trench around the crawl space toroute water away. Thedrainage system looks like this:

In a house with a basement, this same sort of drainagesystem is added along the bottom of the walls. Thebasement walls are then generally insulated with rigidfoam board and then heavily waterproofed before dirt isbackfilled against the walls.

Floor

The framing crew is the next group of people on the site.They start by building the floor (unless the house uses aslab foundation, in which case the slab is the floor).

The floor framing looks like this:

The floor starts with a sill-plate made ofpressure-treatedlumber in direct contact with the bricks of the crawl spacewall. One interesting thing to note is that this houseliterally "sits" on the foundation -- it is not held on or
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bolted on in any way. Then the floor is constructed on thesill with 2x10 lumber:

You may have noticed the brick posts when you saw thepicture of the foundation. They hold a beam that runsdown the center of the house. The beam is also built from

2x10 lumber (three pieces thick):
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All of the "joists" (as the 2x10s in the floor are called)meet on this center beam:

(In many houses the meeting of the joists is somewhatbetter organized!)

This funny little cantilevered section of the frame willeventually hold the fireplace:


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Once the floor framing is complete, it is covered with 1/2-inch or 5/8-inch plywood or OSB (oriented strand board).

And the floor is finished.

Walls

The framing crew next starts on the walls. Walls areassembled on the floor

and then raised into place. Here's what the first wall lookslike once it is up:
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You can see that this wall is made of 2x4 lumber andcovered on the outside with an OSB sheathing.Using plywood or OSB as the sheathing gives the wallrigidity -- you may have seen diagonal pieces used at thecorners of older homes (homes built before plywood was

widely available). The plywood does the same thing, butit provides much more strength.

The 2x4s are placed on "16-inch centers," meaning thatthe center of one 2x4 is 16 inches away from the centerof the next. In this wall, two things interrupt theconsistent 16-inch pattern:
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Windows Special framing that will accommodate internalwalls once they are built

Here's a shot that shows these two features in better

detail:

The plywood will be cut out of the window openings as

construction proceeds. Above the window is a2x10header, which is actually two 2x10s with a piece of1/2-inch-thick plywood sandwiched in between and a 2x4along the bottom.

A cross section of a header is shown at theright. The reason why the header has plywoodin the middle is simply to make the header aswide as the rest of the wall. A 2x4 is really 1-1/2inches by 3-1/2 inches, and a 2x10 is really 1-1/2 inches by 9-1/2 inches. When you sandwich


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two 2x10s together they are only 3 inches wide. Addingthe piece of plywood in between makes the sandwich 3-1/2 inches wide.

A 2x10 header is a beam. You see these headers over allwindows and doors -- they give the wall enough strengthover the window or door to support the roof. When aheader spans more than 5 feet, you find double full-length studs on either side of the header instead of thesingle studs seen here.All of the exterior walls go up following this same basicpattern. In the corners, the top plate on one wall overlapsthe top plate of the next, and the walls are nailedtogether to bind the corner. Then the interior walls go up,fitting into the top plates of the exterior walls as shownabove.

This house has a garage and a breezeway connecting thegarage to the house.
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The walls of the garage are built slightly differently(because the garage will have a slab floor). The walls arebolted directly to the brick foundation walls:

Here's how the house looks right before the roof framingstarts.


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You can see that the framers have covered the outside

walls in pink house wrap.

Roof

This house uses trusses for the roof framing. Trusses arepre-fabricated, triangulated wooden structures used tosupport the roof. The alternative is to build up the roof'sframe with 2x8s and 2x10s. Trusses are quite commonthese days because they have five big advantages fromthe builder's standpoint:

Trusses are incredibly strong.


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Because they are built strictly from shorterlengths of 2x4 lumber, they are generally a lot lessexpensive than the alternative. You can have just about any shape custom-

built, and this allows interesting features likecathedral ceilings at low cost. You can span a large distance with a truss andthe truss transmits all of the weight to the exteriorwalls. Therefore, none of the interior walls are"load-bearing," so they can go anywhere and areeasily moved later. Trusses go up quickly!

From the homeowner's standpoint, the one bigdisadvantage is that you don't have any attic space.

Trusses come in several standard configurations:

"W" truss

"M" truss
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"Scissors" truss

"Gable" truss

Gable trusses are used at the ends of the roof (theoutermost trusses on either end). The vertical pieces are16 inches on center so that siding can be nailed on. Oursample house uses a custom truss in the main part of thehouse that looks like this:

The left-hand side will provide a cathedral ceiling over theliving room. Scissors trusses are used for the front room,and M trusses are used over the garage. Gable trussesare used at the ends of the three rooflines.

The trusses are fist stacked on top of the walls, either byhand or with a crane.
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These trusses went up in about four hours. They are on24-inch centers.


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The trusses are tied to the walls with small metal plates.

Once the trusses are up, the roof is covered in plywood orOSB, which gives the roof tremendous rigidity.


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There are two small custom roofs in this house: the roofover the porch (see next section) and the roof over thebreezeway.

Roof framing without trusses is actually fairlycomplicated. The angles found in anything but thesimplest roof become intricate.

.
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Then a floor goes on top of the frame.

Here are the trusses of the roof over the porch:


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Roofing

This house uses standard asphalt shingles for the roof.The first step is to cover the roof with building paper (tar

paper):

The shingles then go on very quickly (on this house, inless than a day):
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In the following shot you can barely detect the ridgevent that runs along the peak of the breezeway roof.

There is a vent like this along the peak of all the roofs.

This vent replaces the triangular "gable-end vents" foundin older homes. Ridge vents give better circulation(especially when cathedral ceilings are used) and alsoprevent bats and squirrels from getting into the attic.In the following shot, you can see the aluminum flashingthat keeps water away from the walls at the points wherethe shingles touch the walls.

At the edge of the roof, the shingles are cut off with about2 inches of overhang.

THE ARCHITECTS WORK
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The archiotect designs the floor plan of the house for thebuilders to work with. Examples of hose plans and blueprints are below.


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Documents

Tech Drawing Project