SCHOOL OF ARCHITECTURE, BUILDING AND DESIGN

BACHELOR OF QUANTITY SURVEYING (HONOURS)

Construction Technology 1 (QSB 1514 / BLD60104)

Submission Date: 18 June 2014

Group Members

: Moy Chin Hoong 0314014

: Khor Seem Leng 0315208

: Vivian Tan Fui Vun 0318270

: Cassandra Wong Xin Yue 0313365

: Muhammad Haziq bin Hj Zariful 0314131

Table of Content

Content Page

Introduction 1

1) Photos & Drawings 2

2i) Type of foundation 15

2ii) Type of slab 18

2iii) Type of roof 21

3i) Alternative for foundation 22

3ii) Alternative for slab 24

3iii) Alternative for roof 26

References 30

Introduction

Our group has chosen a bungalow house as the object of study in this assignment.

The building is situated in Penang. This assignment consists of three parts. Part I includes

the plans of the type of building we studied; Part II consists of more detailed information

regarding to the building, which includes the identification and illustration of types of

foundation, slab and roof of the building in this project; Part III shows the comparison of

the existing type of foundation, slab and roof with another two alternatives respectively,

from which we choose one suitable option to replace the existing ones. This assignment

has given us an opportunity to learn and do more research regarding to construction,

exposing ourselves to the construction industry and gaining more ideas on the foundation,

slab and roof of various building constructions.

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2i) TYPE OF FOUNDATION

Foundation is the base, which a building is built on. Its purpose is to support the building

by transferring the load from the building down to the soil below the ground. There are

two categories of foundation such as shallow foundation and deep foundation.

Shallow foundation:

- Not deep, normally a meter below the ground.

- Transfer the load to the soil below the ground at a point, which near to the ground

floor of the building.

- Examples are strip foundation, raft foundation.

Deep foundation:

- Deep into the ground, usually used for multi-storey building.

- Transfer the load of the building to a deeper layer of soil, which has a higher

bearing capacity.

- Example is pile foundation.

There are 5 basic types of foundation such as strip foundation, trench foundation, raft

foundation, pile foundation and pad foundation.

Strip foundation:

- Continuous strip of concrete provides a continuous ground bearing under the load

bearing walls

Trench foundation:

- More economical than strip foundation

- More in shrinkable clay soil

- Greater resistance

- Time saving due to fast completion with concrete trench fill

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Raft foundation:

- Expensive

- Act as a single unit, usually used when the structures of the building are close

together

Pile foundation:

- The piles used normally are produced by timber, steel or concrete.

- Common length of 3m, 6m or 12m.

- Pile cap connects piles together and distributes the load evenly

- Square pile is used normally because it is more economical compared to spun

pile.

Pad foundation:

- Usually in square shape due to low cost

- Supports and transmits load from piers and columns

The foundation used for this building is a pile foundation, which is

also a deep foundation. Pile foundation is the combination of piles

and pile caps. The pile caps gather the loads transferred from the

columns of the building and then distribute the loads evenly to the

piles and finally to the soils. There are a total of 15 pile caps (4

units of pile cap that only consists of 1 pile; 9 units of pile cap that

consists of 2 piles; 2 units of pile cap that consists of 3 piles) in the

foundation of this building as shown in the drawing.

The pile foundation chosen is an end bearing pile. The

shaft of end bearing pile passes through the soft deposit

until it reaches and rests on a hard surface or bedrock.

While, the friction pile requires to be embedded in solid

and firm soil. The pile gains its support from the skin

The excavation site

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The piles (2 piles)

friction between the soil and the shaft. As the soil at the proposed site is soft and not

sticky, therefore end-bearing pile is used.

There are few reasons why the pile foundation is

used as the foundation of this building. First, the

original soil at the proposed site is compressible.

It is too weak to provide enough energy to support

the load of the whole building. Since the building

is a double-storey bungalow plus the condition of

the soil is weak and compressible, so it would be

better to use pile foundation in order to provide a

strong base to support the load of building.

Besides, a deep foundation is used because of the

poor bearing capacity of shallow foundation, which unable to support the whole

superstructure loads.

The formwork for pile cap

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2ii) TYPE OF SLAB

Slab is a flat piece of concrete, typically used as a walking surface, but may also serve as a load bearing device as in slab homes.

Function of slab:

Provide a flat surface Support load Sound, heat and fire insulator Act as a divider for the occupants Space between slab and ceiling can be used to place building facilities

Type of Slab

The type of slab used in ground floor and first floor level of our project is suspended slab. A suspended concrete slab is a floor slab where its perimeter is, or at least two of its opposite edges are, supported on walls, beams or columns that carry its self-weight and imposed loading. Suspended slabs are not in direct contact with the ground. They are made of concrete and steel mesh, which are normally pre-fabricated offsite.

Suspended slabs are commonly used to create floors for the upper storeys of houses, but can also be sat on top of pre-constructed walls to form a ground floor. The bungalow in this project is built on a small hill and suspended slabs are used as they exert stability on ground level in hilly terrain.

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2iii) TYPE OF ROOF

HIP ROOFHip roof, also called hipped roof, roof that slopes upward from all sides of a structure, connecting the walls of the building, having no vertical ends. Trusses are found in the interior of the roof, designed with short ridge boards, having several types of rafters: hip rafters, jack rafters & common rafters.

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There are many different variations on the basic 'hip roof' design, created mostly to suit different styles of house.

Hip and Valley Roof

Hip Roof

HIP AND VALLEY- The hips and valleys on a hip

and valley roof describe the points where the different

parts of the roof meet.

BROKEN HIP AND VALLEY - Almost the same as a hip and valley

roof, except that the roof is not level - some ridges and

points are higher than others.

BELCOTE - has a verandah attached that runs all the way around

its perimeter.

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The type of roof being used in our project is hip and valley roof .

A hip & valley roof is simply a modified or extended hip roof. The shape and pitch of the surfaces are basically the same. The hip & valley roof has an additional ridge, which joins the main roof ridge at the same height, which creates a single valley for an ‘L’ shaped roof. It may also join the roof surface at the same height or at a lower level on a side or end, without connection to a hip, creating two valleys for a ‘T’ shaped roof.

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3i) ALTERNATIVE FOR FOUNDATION

Definition

Pad foundation is defined as a type of shallow foundation with a thick slab type foundation used to support a structure or a piece of equipment. It is used to support a point load such as columns or framed structures. They may be circular, square or rectangle and consists of a block or slab of the thickness. The pad foundation may be stepped or hunched if they are required to spread the load from a heavy column. The pads are usually shallow but deep ones can be found depending on the structure.

Trench foundation is defined as a type of foundation that uses loose stone or rubble to minimize the use of concrete and improve drainage. 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 insure good soil drainage, the rubble trench foundation serves both foundations at once.

Advantages of Pad Foundation

- Cost is affordable- Construction procedure is simple- Mostly concrete- Labor does not need expertise

Disadvantages of Pad Foundation

- Settlement- Limit capacity soil structure

Advantages of Trench Foundation

- Cost is cheaper- Uses lose stones or rubble to minimize the use of concrete and improve damages

Disadvantages of Trench Foundation

- Needs to be in well-drained soil where the water table is below the bottom of the rubble trench.

Cost

Trench Foundation

For pad foundation, the cost of the finished structure may cost a little more than trench foundation. The reason for this is because in trench foundation, lose stones and rubble are used instead of 100% concrete. In pad foundation, mostly concrete is used and hence, the price is a little more than trench foundation.

Thickness & Types of Foundation

For thickness, trench foundation is definitely thicker than pad foundation. In pad foundation, a thick gravel pad that is significantly wider than the house itself is used to stabilize the ground and spread building loads. As for trench, a deeper foundation provides greater resistance to fracture from unequal settlement. There are four types of pad foundation; mass, hunched, reinforced and stepped. For trench foundation, there are two types, concrete and rubble.

Soil Condition

In pad foundation, the soil on it must be able to resist the loads from the foundation with equal and opposite forces. The soil therefore needs to have enough compressive strength and shear strength to prevent contraction and sliding within the soil. In trench foundation, soil with poor load bearing are not suitable for this kind of foundation, but it is suitable for poor quality sands and sandy slits.

Types of foundation Pad foundation Trench Foundation

Cost Affordable Cost lesser

Size/thickness Wide & Shallow Wide & Thick

Soil Condition Must be strong enough to withstand strength

Used in poor conditioned soil

Conclusion

In our opinion and based on all the points, pad foundation is more suitable to replace pile cap because the price is affordable, the size is thick and shallow and is suitable for housing area. In addition, pad foundation is used because the original soil at the proposed site is compressible to provide enough support for the load transferred from the whole

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Types of Pad Foundation

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building and therefore trench foundation cannot be used. Conclusion, pad foundation is chosen to replace pile cap.

3ii) ALTERNATIVE FOR SLAB

Suspended Slab

Advantages

Can be used where other slabs can't - for example, on steeply sloping terrain Allows access to under-floor areas Relatively easy to install once the supports and machinery are in place More effective than bearer / joist sub-floors in blocking out noise from upper

floors

Disadvantages

Requires crane access Not as well insulated as a ground slab, as the base doesn't touch the ground

Non-suspended Slab

Definition

Non-suspended slabs are primarily made of concrete, though other materials like steel mesh or rebar are also incorporated to add strength. These foundations are generally used to support heavier building materials like brick and steel. They are suitable to be used on stable ground with presence of sand and rock, which is not affected by moisture. These ground slabs can also be used on sites with slightly reactive soil.

Advantages

Extremely durable and hard base for a floor Typically well insulated, because the underside of the floor is not exposed No maintenance needed once the concrete has cured

Disadvantages

Impossible to access piping once the slab has cured Cracks can cause major structural damage, and may be un-repairable Might create unwanted noise

Waffle Slab

Definition

A waffle slab is a type of building material that has two-directional reinforcement on the outside of the material, giving it the shape of the pockets on a waffle. These slabs are used as the foundation for many different types of buildings and structures, but are most common in commercial or industrial buildings. Waffle foundations are resistant to cracking and sagging and can hold a much greater amount of weight than traditional concrete slabs.

Advantages

Less concrete and reinforcement required

Reduce cost by reducing the number of beams and columns required

Strong, lightweight moulds, capable of supporting all the normal loads encountered in building works

Use prefabricated standard forms

Disadvantages

More time is needed when creating forms

Difficult to lay rebars and connect them to beams

Recommendation

From the above information, the alternative chosen to replace the existing type of slab is the waffle slab. The waffle pod slab design gives a better way to build slabs using higher accuracy when it comes to the different concrete specifications. The system also aids in the reduction of waste during the production because it has minimal, if any, harmful effects to the surroundings. This particular design uses less soil disturbance in comparison to other designs. One of the advantages of the waffle slab that attracts contractors, property owners, and construction firms is the reduced cost that comes with it. The waffle slab design is basically the use of concrete slabs which are placed on the

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ground. These are arranged in a sort of pattern that forms a grid, hence the impression of looking like a waffle

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3iii) ALTERNATIVE FOR ROOF

Installation

One of the biggest advantages of a gable roof is that they are relatively simple and economical to build. Gable roofs have two faces, whereas hip roofs have four & gable roofs are designed with two sets of parallel rafters attached to the trusses, meeting at the ridge board while a hip roof is designed with a shorter ridge board, and has several types of rafters. Due to the above, constructing hip roofs involves more construction & knowledge than gable roof. Both roof types require precise measurement, cuts and installation, but hip roofs have more elements that can go wrong.

An advantage of installing rubber flat roof is, instead of individually placing shingles in addition to the construction of trusses or support under the roofs like hip roofs, large measured & cut rubber rolls are used after cleaning the surface, making it quicker to install, however, rubber roofs in general needs to be installed by a professional with experience, which can be

difficult to find and costly.

Space

The design of a gable roof allows for extra living space above the home's top floor compared to a hip roof on the same plan. Gables are typically constructed for use as an attic, although they can be transformed into extra living space. The extra space can also help with access for the maintenance of the roof.

Unlike its sloped counterparts, rubber flat roofs allows the building to have plenty of usable outdoor area on top, giving space for many useful & beneficial assets, mostly irretrievable even through

Installation of Rubber membrane

Comparison of space under roof between Hip & Gable

26 |Solar panels & Gardens atop a flat roof

the use of gable roofs, such as outdoor patios, gardens, water storage tanks, vents or even solar panels. The shape of the roof also allows the convenience of maintenance by just climbing up to inspect the roof.

Cost

One of the main advantages to having a gable roof is its cost. The fact that gabled roofs are easy to build and are popular roofs on the market has created competition that have helped drive the cost of these roofs down, making them more affordable than most other types. Because a hip roof has a more complex structure, a contractor will spend more time constructing it. This is why a hip roof is more expensive than a gable roof.

In addition to the raise of cost through employing an expert for installation, the rubber flat roof is expensive compared to other materials such as modified bitumen. Despite that, an expert can finish installation quickly, reducing construction cost compared to hip roofs, while using the more pricey light-colored rubber, which reflects heat, would reduce cooling/heating costs. Furthermore, replacement of the roof takes 30-50 years & along with its stability, repair is done simply.

Suitability & Durability

While gable roofs can facilitate water shedding ability and snow load protection better than hip roofs by using their steeper slope, it is weak however, in wind protection & strength. A hipped roof has greater strength and durability than a gabled roof because of its aerodynamic design, having fewer sharp corners and a shallower slope; it can withstand earthquakes & windstorms. On the other hand, the design of the gabled roof allows the wind to flow under it, which can make the roof literally peel off.

Contrary to popular belief, flat roofs do not have bad drainage, just not as good as sloped roofs. Moreover, it can be suitable to the heat of Malaysia when using light-colored rubber membrane for the roof, as it reflects the heat, also acting as an insulator in the

Gable roof with similar shape as the house

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cold. Leakage is a very common problem flat roof owners face but because the large rubber rolls have no seams and are very durable in extreme weather, the chances of leaks and cracks are extremely low & when leaks do come, they are easy to patch. The material is also highly resistant to scuffs and tears.

Appearance

Gable roofs differ greatly in look from hip roofs. Gable roofs allow for fully exposed sides, while hip roofs sit atop the boxed structure, revealing the same amount of siding on all sides. This helps the hip roof however, to provide installation of gutters around the perimeter of the house. Yet, the exposed side of the gable can provide windows for the extra room or a dormer room.

In contrast to gable roofs, rubber flat roofs offer a more drastic change in appearance. Flat roofing consists of a horizontal base which is fixed to the ceiling joists underneath with a waterproof membrane applied on top whereas sloped roofs uses shingles with a vertical rise, a slope, meeting the sides of the structure. Flat roofs also give an appealing appearance, as mentioned before, the use of a rooftop garden or patio can boost the aesthetics, compared to sloped roofs that cannot hold such assets.

The beneficial layers of a rubber flat roof

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Hip & Valley Roof Gable & Valley Roof EPDM Rubber Flat Roof

Installation Involves more construction & knowledge

Simpler & more economical to build

Uses rubber rolls & quicker to install

Space Trusses structures under the roof, can contain chimneys

Extra space for attic or extra room & access for maintenance

Can place beneficial objects that settle on flat surfaces

Cost Complex structure & more construction time causes costly price

Reduced price due to popularity & easy construction

Costly at first, but beneficial in the long run

Durability Design causes wind protection & strength, arguably the best among roofs

Very unsuited to windy areas due to design, which can peel off the roof

Rubber layer makes it durable for extreme weather, scruffs, tears & leakage

Suitability

(To environment of original house)

Decent rain runoff ability, longer eaves for shading.

Steep slope makes it the best among roofs for water runoff

Heat absorption & insulation, suitable for Malaysia’s dry & wet seasons

Appearance Roof connects with walls & has 4 slopes, allowing use of gutters

Fully exposing 2 sides allowing extra room hence allows extra windows

Horizontal base & appealing looks when patio & gardens are placed

Verdict & Recommendation

It is recommended, in an environment such as Malaysia, where sunny days are hot & rainy days are cold, that EPDM flat roof would be the better roof alternative for the building, economically, aesthetically & environmentally better. One of the justifications being the ease of installation; which would result in a lower construction cost, despite the extra for the need of an expert, also lowering cost in the long run for maintenance due to its durability. Its ability to reflect & insulate heat can benefit the owner during the hot sunny & cold rainy days respectively. The house is located in a residential area, so there are no areas for gardens & patios, flat roofs offer the space needed to place them, also boosting aesthetical value when reselling or renting.

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