Construction technology and services 1

Name: Sara Saeid

Department: Architectural Engineering

Student ID: 738660

1

CONTENTS:

Task (1) Site investigation and ground works

The definition of site investigation The performing way of site investigation The stages of site investigation clay soil investigation The properties of clay Sketches of ground works suitable safety precautions during ground works

Task (2) Foundations

Drawing to a scale 1:5 of a cross section for suitable foundation for the external cavity wall.

Foundation types and selection.

Task (3) external walls

Detailed drawings of scale 1:5 a cross section through the masonry wall at window opening shows the details at the lintel and the Cill.

Sketches indicate the construction of the cavity walls. Alternatives to insulated cavity walls that provide a high level of

thermal insulation. the implications of the alternatives wall insulations

Task (4) Ground and upper floors

Detailed drawing to a scale 1:5 showing the construction of the suspended concrete beam and block ground floor at the junction with a cavity wall.

Detailed drawing to a scale of 1:10 in 3D. Showing suitable upper floor construction and the connection with the cavity wall.

Sketches illustrate the building regulation requirements for upper floors in accordance with Approved Document A.

The introduction:

2

This report is a clear explanation of all the stages of a house construction. It will discuss the likely issues with regard to the actual site that has been provided. Firstly, a site investigation would be done to ensure that the site is suitable to build on. This would include a soil investigation to find out the properties of the soil and how it could affect the foundation or the whole structure. Some sketches and drawings would be done to indicate different step of the construction in addition to the materials and components that are used. As well as this all types of foundations will be explained in details and illustrated by pictures. The aim of collecting all these data is making the right choice of materials and construction that can suit the actual site.

Task1 (A):

What is site investigation?

A site investigation is always required for any engineering or building project to determine the suitability of the site and its environment.

The way that this type of investigations work?

It is about collecting systematically and record all the necessary data which will be needed or help with the design and construction process of the proposed work. The collected data should be presented in the form of fully annotated and dimensioned plans and sections. Anything on the adjacent sites which may affect the proposed works or conversely anything appertaining to the proposed works which may effect on the adjacent site should also be recorded.

Now From a site investigation perspective there are some issues that we have to consider prior to building upon this particular site:

1. The type of the site (greenfield or brownfield):

3

Greenfields:

Are sites which have not previously been built on. This includes the greenbelt land around cities.Some issues that are related to a Greenfield site:

1. Infrastructure already exists in urban areas- in Greenfield sites new drainage, electricity, roads etc. would all have to be produced.

2. It is not favoured by environmentalists, as it encourages urban sprawl.3. Providing public transport networks is easier in central areas where the

population densities are high- investment is focussed in central areas and much Harder in most of Greenfield sites.

4. Using Greenfield sites is not sustainable- there is too much pressure on the rural-urban fringe and the use of Brownfield sites has to be a better option.

5. Towns and cities do not want their areas to decay- redevelopment results in more people coming to the area, which helps local businesses. Building on Greenfield sites ‘sucks’ out the core from towns as shop.

This a picture of Greenfield site:

Brownfields: A site that has been built on before. Normally associated with urban areas.

As the case with the Greenfield sites there are some issues that are related to building on a Brownfield site:

1. New housing can lead to gentrification (old housing done up- area becomes more trendy and affluent) so the area will improve and things like crime rates will improve.

2. New sites are easier to build on as there is a fresh start, where remains of previous land use do not need to be cleared and is more attractive to retail parks, housing developers.

3. There is an issue of contamination and making sites safe for development, given what the land may have been used for before.

4. Greenfield sites are often on the edge of towns and cities and may have better access, have less congestion, be in a more pleasant environment and have more space and room to expand.

4

This a picture of brownfields site:

2. The location of the site: a. Residential, commercial, industrial, or rural area?b. Details of local authorities, full data as to type size, depth and location of all

services such as gas, water, drains, electricity, telephone and relay services, c. How much sun light is available at the site, (is there any possibility of using solar

heating?) d. Are there any protected species on or near the site that might have an effect

upon the site?e. Adjoining roads, and other contracts in the area, local transport (where are the

nearest public transport).f. Local flooding or subsidence, environmental and ecological considerations.

3. Ground condition: a. General topography (the natural of the ground) including the approximate slope as

this affects the design of the structure and the drainage system.b. Soil investigation:

Investigate the subsoil beneath the site under investigation to find out the main properties of the soil.

The purpose of soil investigation is to determine: The stability of the site for the proposed project. An adequate and economic foundation design. The difficulties which may arise during the construction process period. The occurrence and/or cause of all changes in subsoil conditions.

Ground contamination, contaminated land may present a hazard to potential users of the land or to the environment. Users may become exposed to contaminants such as by inhalation of dust or gases or contact with soil, also through food grown on the land. There may be indirect effects on users such as damage to buildings. Substances can be washed out of soil (leaching) to pollute groundwater, rivers or ponds. Some contaminants may be corrosive, and some can cause explosion or fire.

Vegetation, Tree Preservation Orders, leaning trees. Underlying geology, mines or quarries, rock outcrops, rubbish on the site.

5

4. Existing building or trees on or adjoining the side:

a. Previous history, old foundations, demolition.b. Condition of existing buildings, the importance of this consideration is for some

reasons: Shading from neighbouring buildings. Causing unreasonable shading to neighbouring buildings. Loss of privacy for occupants or neighbours.c. Defects- cracks, out of plumb and embankments, and those adjoining the site,

effect on positioning of scaffolding, formwork (temporary works), (Take photos of both, helps pricing and avoidance of scams.).

d. Existing trees, type, girth, spread and height. The most considerable issues with the adjacent tree would be:

Whether roots are under or can get under foundations. The capacity of those roots to abstract moisture.

To determine the possible impact of the trees on the adjacent buildings, some studies and experiments have been done. This table of appropriate distances between trees and property used by the ISE and the Loss Prevention Council is based on P.G. Biddle’s water demand classification of tree species. This in turn was based on a combination of his own case studies, the findings of the Kew Root Survey, (significantly updated in 1989), the experience of the BRE digest and several other older studies.

Common Name

Latin Name

Max. tree-to- damage distance (m)

Distance within which 90% of damage cases were found (m)

Distance within

which 75% of damage

cases were found

Willow Salix 40 18 11Oak Quercus 30 18 13Poplar Populus 30 20 15Elm Ulmus 25 19 12Horse chestnut

Aesculus 23 15 10

Ash Fraxinus 21 13 10Lime Tilia 20 11 8Maple Acer 20 12 9Cypresses Cupressus

&20 5 3.5

Hornbeam Carpinus 15 10 -Plane Platanus 12 11 7.5Beech Fagus 12 11 9Hawthorn Crataegus 11 9 7Rowan & whitebeam

Sorbus 11 10 7

Cherries Prunus 11 8 6Birch Betula 10 8 7Elder Sambucus 8 - -Walnut Juglans 8 - -Laburnum Laburnum 7 - -Fig Ficus 5 - -Lilac Syringia 4 - -False Robinia 13.5 10 8.5

6

AcaciaApple Malus 10 8 6Pear Pyrus 10 8 6

The result:All species of trees are simply categorized as, “high”, “moderate” or “low” water demanders. Species in the high group are generally considered to extend their influence on soil moisture levels over a distance of 125% the height of the tree. Moderate water demanders such as sycamore and cherry extend their influence over 75% of their height and low water demanders such as holly and beech extend their influence over 50% of their height.

5. Waste : Distance to local tips, tipping fees, (particularly for special waste), Recycling, if there any possibility of re-use of site materials?

6. Site access: Restricted site access, low bridges, restrictions on local bridge weights, busy roads, local road upgrades, temporary roads, positioning of temporary works, site boundary problems requiring crane easements, Offloading problems (temporary works).

7. Working space : Restricted site, positioning of site accommodation, lay down areas for materials storage, site car parking, one way traffic systems on site, adjoining land available to rent for contract duration.

8. Existing services : Location of foul / surface manholes on site and local roads, electricity supply (Junction Boxes), lighting columns water (stop taps), gas, cable, telegraph poles, phones, overhead cables, temporary services needed, services easements.

9. Local labour : Availability of skilled labour, local subcontractors, job centre, agencies, local rates of pay, availability and cost of lodgings, transport provision in relation to the labour catchment area.

10. Local materials and Suppliers: Availability and quality of materials, size of and costs for local builders’ merchants and plant hire companies .

11. Site security: Assess need for and extent of site fencing, site lighting, security patrols, night security, Herras fencing, Close boarded hoarding, chain link, steel palisade.

7

Task1 (B):Moving to the likely problems that the ground which is clay in this site could have on the foundation.

Clay:The first 900-1,200mm layer of clay is subject to movement due to expansion and shrinkage depending on moisture content. In clay, prior to concreting the foundations, the trench is often protected from heave by lining it with a compressible layer (e.g. Clayboard).

There are some soil properties that are critical to evaluate before building on a

Specific area of land:

1. Surface texture: Surface finish, also known a surface texture or surface topography, is the nature of a surface as defined by the three characteristics of lay, surface roughness, and waviness. It comprises the small local deviations of a surface from the perfectly flat ideal.Fine-textured soils as clay have a tendency to expand as the amount of moisture increases and to contract as moisture decreases. Cracks at the soil surface are evidence of this during dry periods. This same expansion and contraction takes place during the winter and spring as the moisture in the soil freezes and thaws. This lack of stability can crack foundations, sidewalks, and driveways if precautions are not taken.

This table shows different types of soil texture and the available water capacity on them.

8

2. Permeability:

Can be defined as the ability of a porous mass to allow passage of water through the medium.There are some factors that affect the permeability of a soil, for instant, particle size, impurities in the water, void ratio, the degree of saturation, and adsorbed water, to entrapped air and organic material. Based on the fact that clay consider as a fine grained soil (has not a lot of voids through it) therefore it has much less permeability comparing to coarse grained soils (has more voids through it). The consideration of the permeability is very important prior to any structure. Because once a foundation is laid, you don't want the soil mass holding your foundation to leak water.

3. Depth of soil to bedrock: In the case of an expansive clay, some special techniques wold be required. Usually buildings placed on sites with expansive clay require pile foundation extending down to a suitable soil strata or bedrock. To insure the stability of the building during the changes in the clay (shrink and swell) as a result of being exposed to seasonal changes.

4. Slope: Surface degradation processes and local landslides occur frequently on slopes excavated in soft rocks. As a result, safety of facilities at the bottom of these slopes is threatened and the cost of maintenance or supporting is usually significantly high. At the same time, the stability of facilities located at the top of such slopes is also submitted to increasing risk. The excavation work in these geomaterials (mostly clayey rocks, such as marl, siltstone, mudstone, shale, claystone, etc.) can be performed only with use of heavy machinery (rock breaker) or explosives, as well as in other types of rocks.

9

5. Erosion hazard: Erosion is caused by wave action, water currents, winds that fuel wave action, water flow over land and through points of groundwater discharge and the freeze-thaw activity in winter and especially in spring. Temporary fluctuations in water levels from storm events or storm-induced surges producing elevated wave activity are the principal causes of coastal bluff erosion.

6. Surface runoff: Surface runoff (also known as overland flow) is the flow of water that occurs when excess storm water, meltwater, or other sources flows over the earth's surface. This might occur because soil is saturated to full capacity, because rain arrives more quickly than soil can absorb it, or because impervious areas (roofs and pavement) send their runoff to surrounding soil that cannot absorb all of it. Surface runoff is a major component of the water cycle. It is the primary agent in soil erosion by water.

7. Shrink-swell of the soil.

A clay subsoil can be considered to behave similarly to jelly. The overall volume of the subsoil (or jelly) is largely dependent upon the amount of water that is bonded at any given time to the clay minerals (or gelatine). The soil (or jelly) will shrink if water is removed and then subsequently expand if water is reabsorbed. This expansion ceases when the clay achieves its former or a new state of equilibrium, i.e. when there is no longer a negative pore pressure to draw additional moisture into the soil. It is important to appreciate that the solid particles do not shrink. Volume change is totally dependent upon variation in moisture content.For a clay subsoil the natural (or equilibrium) moisture content is dependent upon itsgeological history. If any water is withdrawn the clay by definition becomes desiccated –that is drier than in its natural state. It follows that a reduction in moisture content will be accompanied by clay shrinkage and the soil does not have to attain a state of ‘significant desiccation’ before clay shrinkage commences.

Task1 (c):

I have done the sketches to illustrate some groundworks.

Labelled as Drawing (1)

There are some suitable safety precautions that are necessary during the ground work in the site.

a. In case of open excavations: Provide temporary support or timbering to the sides of the excavation. This

can be intrusive when the actual construction of the basement floor and walls is being carried out. One method is to use battered excavation sides cut

10

back to a safe angle of repose thus eliminating the need for temporary support works to the sides of the excavation.

In economic terms the costs of the plant and manpower to cover the extra excavation, backfilling and consolidating must be offset by the savings made by omitting the temporary support works to the sides of the excavation.

b. In case of trench excavations: In this method it might be necessary for runners or steel sheet piling to be

driven ahead of the excavation work. This method can be used where weak subsoil are encountered so that the basement walls act as permanent timbering whilst the mound or dumpling is excavated and the base slab cast. Perimeter trench excavations can also be employed in firm subsoils when the mechanical plant required for excavating the dumpling is not available at the right time.

Task 2 foundations (a):

I have done a drawing of scale 1:5 (cross section of suitable foundation for the external cavity walls, given the soil is firm clay and shows the below ground level walling on the foundation)

Labelled as Drawing (2)

Task 2 foundations (b):

There are some types of foundations and every one of them has its own properties. Therefore, there are used in different sites.

1. Raft foundation:

Raft foundation is a large slab supporting a number of columns and walls under the entire structure or a large part of the structure to lower the contact pressure compared to spread footing. The advantages of raft foundation:

a) Raft or mat foundation is economic due to combination of foundation and floor slab.

b) It requires little excavation. c) It can cope with mixed or poor ground condition d) It reduces differential settlement.

The disadvantages of raft foundation:a) Edge erosion occurs if not treated properly. b) Mat foundation requires specific treatment for point loads.

11

Figure 1raft foundation

Types of raft foundation:

a) Solid slab raft foundation:Is a solid reinforced concrete slab generally of uniform thickness, cast on subsoils of poor or variable bearing capacity, so that the loads from walls or columns of lightly loaded structures are spread over the whole area of the building.

Figure 2solid slab raft foundation

b) Beam and slab raft foundation:This raft consists of upstand or down stand beams that take the loads of walls or columns and spread them to monolithically cast slab, which bears on natural subsoil.

Figure 3beam and slab raft foundation

c) Cellular raft foundations:This type of raft consists of top and bottom slabs separated by and reinforced with vertical cross ribs in both directions.

12

Figure 4 cellular raft foundation

The cost:It considers expensive comparing to strip foundation.

2. Strip foundation These are the most common foundation found in residential buildings, they are used mainly on sites were you have a strong soil base and were waterlogging is not very common.

The advantages of strip foundation: A. Cheap because of the lack of manual labour required to make it. B. It requires no form work C. Reduces brick laying below ground level so bricks do not get damaged by

moisture in the soil. D. Avoids excessive depth

The Disadvantages of strip foundation:

A. Needs more concrete reinforcement compared to pad foundations B. They have to be designed similar to steal beams when it comes to

building movements.

13

Some properties: A. Strip foundations consist of a continuous strip, usually of concrete,

positioned under load bearing walls. B. This continuous strip serves as a level base on which the wall is built

on.C. Strip foundations are used where the soil is of good bearing capacity.D. The inner load bearing block wall will stay the same to the concrete

foundation whereas the brick will change to either block as there is no need for a facing block in the substructure.

E. The minimum thickness for the concrete strip is 150mm and 450mm deep and wide.

Types of strip foundation:A. Deep strip foundations: where strip foundations need to be at a lower

level to reach soil with suitable bearing capacity. B. Wide Strip Foundations: where the soil is soft or of a low load-bearing

capacity, it can be used to spread the load over a larger area.

Figure 5 wide strip foundation Figure 6 deep strip foundation

14

3. pile foundation:

Pile is a long slender foundation member, made either of timber, structural steel or concrete. It is described as piled when its depth is more than three times its breadth.

Figure 7 pile foundation

The advantages of pilled foundation:A. Piles can be precast to the required specifications. B. Piles of any size, length and shape can be made in advance and used

at the site. As a result, the progress of the work will be rapid. C. A pile driven into granular soil compacts the adjacent soil mass and as

a result the bearing capacity of the pile is increased D. The work is neat and clean. The supervision of work at the site can be

reduced to a minimum. The storage space required is very much less.

The disadvantages of pilled foundation:

A. Precast or prestressed concrete piles must be properly reinforced to withstand handling stresses during transportation and driving.

B. Advance planning is required for handling and driving. C. Requires heavy equipment for handling and driving.

Types of pile foundation:

A. Shallow foundations are typically used where the loads imposed by a structure are low relative to the bearing capacity of the surface soils.

B. Deep foundations are necessary where the bearing capacity of the surface soils is insufficient to support loads imposed and so they are transferred to deeper layers with higher bearing capacity.

15

Figure 8 shallow pile foundation

Figure 9 deep pile foundation

4. Pad foundation: Pad foundations are used to support individual or multiple columns, spreading the load to the ground below. They are generally square or rectangular in plan, with the plan area being determined by the permissible bearing pressure of the soil. The shape in plan will be dictated by the arrangement of the columns and the load to be transferred into the soil.

Figure 10 pad foundation

The advantages of pad foundation:A. The advantage of this system of foundation is that pockets of tipped

stone or brick and concrete rubble that would obstruct bored piling may be removed as the pits are excavated and that the nature of the subsoil may be examined as the pits are dug to select a level of sound subsoil.

B. In simple cases the pad may be constructed from mass concrete. In general, some reinforcement (either welded steel fabric or reinforcing bars, depending on the loads involved) will be required in both directions.

16

The disadvantages of pad foundation:A. Requires more material than the other foundations. B. It does not work with taller buildings, which would affect the design process. C. Concrete takes longer to dry which could hold up the manufacturing stage. D. It is more likely to sink in wetter ground, which effects what sites it can be

used on.

Some properties of pad foundation:A. Used when isolated loads need to be supported.B. To support the columns of a steel or post and beam frame house.C. The load is concentrated in small area.

5. Trench fill foundation:

Trenches are dug to a depth where the subsoil provides sufficient load-bearing capacity, and the whole trench is filled with concreate.

Figure 11 trench fill foundation

Some properties :

A. Steel reinforcement may be added in areas close to trees.B. It minimise the width of the dig and the labour and materials required for

building masonry below ground level.

Task (3) (a) external walls:

I have done a drawing to scale 1:5 (cross-section through the masonry cavity wall at a window opening showing the detail at the lintel and the cill.Labelled as drawing 3

Task (3) (b) external walls:

17

I have done some sketches that show the construction of the cavity walls with specification of the main materials and components that comply with the necessary building regulations approved documents.Labelled as drawing 4

Task (3) (c) external walls:

Examples of alternatives to insulated cavity walls in order to provide a high level of thermal insulation:

A. kooltherm K8 cavity board: As an insulation for partial cavity wall.

Figure 12 kooltherm K8 cavity board

The implications of using it:

Premium performance rigid thermoset insulation – thermal conductivities as low as 0.020 W/m.K.

Negligible smoke obscuration. Class O / low risk fire rating. Clear cavity is maintained – resists moisture penetration. Low emissivity foil facings significantly increase the thermal resistance of the

cavity. Meets NHBC technical requirements when used with a 50 mm residual

cavity.

B. Kooltherm cavity closer / cavity closer plus: Kingspan Kooltherm Cavity Closer is PVC–U extrusion with a fibre free rigid thermoset insulation core that maintains continuous insulation around window and door openings. It is suitable for use with timber, metal or PVC window frames and can also be supplied to order in curved sections. Kingspan Kooltherm Cavity Closer PLUS comprises sections of Kingspan Kooltherm Cavity Closer factory pre–formed into a frame and is designed specifically to reduce the labour and time involved in installing individual sections.

18

Some properties:

Thermal conductivity 0.022 W/m.K

Sheathing PVC-U extrusion J-section

Core Premium performance rigid thermoset phenolic insulant manufactured with a blowing agent that has zero Ozone Depletion Potential (ODP) and a low Global Warming Potential (GWP)

Length 2.4 m

Widths Available 50, 75, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145 and 150* mm*Sections can be joined together to suit

Figure 13 kooltherm cavity closer and closer plus

The implications of using it:

Continuous insulation – maintains a continuous insulated cavity closer around window and door openings.

Passes one–hour fire test with PVC window and up to 150 mm cavities. Passes half-hour fire test with PVC window and up to 300 mm cavities. Simplified construction – avoids the need for cut bricks, blocks or special reveal

blocks. Reduced heat loss – avoids thermal bridging, condensation and mould growth Weather resistant – forms an integral DPC

19

Flexible – can either be built in with frames or used to pre–form openings when frames are fitted later

Unaffected by air infiltration Easy to handle and install Non–deleterious material Insulation core manufactured with a blowing agent that has zero ODP and low GWP

C. Themabate and Thermabate plus: Thermabate Cavity Closer is PVC–U extrusion with a fibre free, rigid thermoset insulation core that maintains continuous insulation around window and door openings. It is suitable for use with timber, metal or PVC window frames.

Some properties:

Thermal conductivity 0.034 W/m.K

Sheathing uPVC extrusion

Core High performance rigid thermoset fibre-free urethane insulation core manufactured with a blowing agent that has zero Ozone Depletion Potential (ODP) and low Global Warming Potential (GWP).

Section length 3.0 m

Profile widthsSingle Flange:Twin Flange:

50, 65, 75, 85, 90 & 100 mm110, 125, 140 &150 mm

Figure 14 thermsbate and thermbate plus

The implications of using it:

20

Continuous insulation –maintains a continuous insulated cavity closer around door and window openings.

Single sections fully filling cavities up to and including 100 mm pass half-hour fire test with a uPVC window frame.

Simplified construction – avoids the need for cut bricks, blocks or special reveal blocks

Inhibited heat transfer – reduces thermal bridging, condensation risk and mould growth

Weather resistant – forms an integral DPC Can be fitted with door / window frames as a combined unit Unaffected by air–infiltration Easy to handle and install Non–deleterious material Insulation core manufactured with a blowing agent that has zero ODP (ozone

depletion potential) and low GWP (global warming potential grading).

D. Alreflex platinum which has a U value of (0.27 w/ m2k):

Alreflex Platinum insulation boards combine the thermal properties of Graphite enhanced EPS with the low emissive technology and vapour resistance of Alreflex foil.

Figure 15 Alreflex platinum

The implications of using it:

ZERO ODP AND GWP<5. SIMPLE INSTALLATION CAN BE SEALED AS VAPOUR BARRIER.

E. Alreflex ultratherm.

21

A 50mm thickness of Alreflex Ultratherm board can achieve a U-Value below 0.24W/m2K in a 100mm cavity.

Figure 16 Alreflex ultatherm board

The implications of using it:

This detail and others shown will easily meet the requirements of Part L 2010 and Code Levels.

BBA Certificated product of a PUR/PIR board laminated to Alreflex 1L, of which 5 million sq. m. has been successfully installed in UK housing.

Unique BBA Certificated cavity rain barrier based on overlapping joints to prevent ingress of water across the cavity. Suitable for all exposure areas.

NO CFC or HCFC gases employed. ZERO ODP (ozone depletion potential). ZERO GWP (global warming potential grading).

F. Alreflex 2L2 FR cavity wall:

Alreflex 2L2 has enjoyed a large scale usage by leading UK House Builders since 1985.

The implications of using it:

Very cost effective solutions can be achieved in combination with Aircrete blocks or thin lining boards.

UNIQUE- rain water barrier. Low cost. More than 20,000 dwellings per year are successfully installed with. ALREFLEX cavity wall insulation. Unique BBA certified Rain Barrier performance. Negligible wastage. Easy to install, handle and store on site. Fire retardant grade as standard.

Task (4) (a):

22

I have done a drawing of scale 1:5 (cross-section showing the construction of the suspended concreate beam and block ground floor at the junction with a cavity wall, including a specification of the main components and damp resistance.Labelled as Drawing (5).

I have done a 3D drawing of scale 1:10 (suitable upper floor construction, showing connection with the cavity wall and illustrate by sketches, the building regulation requirements for upper floors I accordance with approved document A.Labelled as Drawing (6).

References and bibliography: Chudley, R. and Greeno, R. (2014) Building construction handbook. 10th edn. United

Kingdom: Taylor & Francis. Riley, M. and Cotgrave, A. (2008) Construction technology 1: House construction

(building and surveying series). 2nd edn. United Kingdom: Palgrave Macmillan. Thermal - loft - roof - wall - cavity - board - insulation materials - Kingspan insulation

(no date). Available at: http://www.kingspaninsulation.co.uk/Applications/Application.aspx Accessed :(11 December 2015.(

Topic 6: Properties of soil (2006) Available at: http://www.soil-net.com/primary/ks2/topic6/topic6_factsheet.pdf) (Accessed: 11 December 2015(

23