CPCCBC4006A Select, Procure and Store Construction Materials for Low-rise Projects

Building and Construction (building)

CERTIFICATE IV

NSW TAFE COURSE - 19734

Training Package CPC08

CPCCBC4006A

Select, procure and store construction materials for low-rise projects

TAFE NSW Riverina Institute, Albury Campus

Contents
Units
1 / Factors affecting the performance of building materials
2 / Timber & Engineered timber products
3 / Mortars, Concrete & concrete products
4 / Clay products & stone
5 / Plaster, plasterboard, compressed cement products & insulation
6 / Metals & glass
7 / Paints & coatings
8 / Plastics & adhesives
9 / Alternative Materials

Acknowledgement

The composition of these student class notes has been undertaken as to ensure that the original TAFE OTEN notes (NSW) and any updated information from the Building Code of Australia 2008 [BCA] (NSW) provisions, and any other documents, literature and referrals including Australian Standards, are fully explained and are reflected within these notes.

This document is acknowledged as a personal revamp of the above mention information as to provide concise and as current information as possible to the students. I thank my fellow Riverina Institute Building and Construction Teachers for their assistance for some of this information.

UNIT 1

Factors affecting the selection of building materials

Learning Outcomes:

Identify and evaluate the properties of building

·  The suitability of materials commonly used in the region for low-rise buildings is identified for a given building system.

·  The properties of materials, their quality and the compatibility and non-compatibility of different materials are identified.

·  The environmental impacts of different materials are identified

·  The impact of allowable tolerances on the conversion of naturally occurring materials is identified.

·  The tolerances for installing and assembling materials are identified and checked in regard to the nature of the work being performed and the requirements of the Australian standards.

Factors affecting the selection of building materials

In this section you will learn about the characteristics and quality standards of building materials commonly used in residential scale buildings. This knowledge will help you to select the most appropriate materials for your work.

We will examine a wide range of building materials: timber and timber products, concrete and concrete products, clay and stone, mortars, plaster and plasterboard, metals and glass, paint and coatings, plastics and adhesives and alternative materials. Before we examine each of these materials you will need to know what affects the performance of building materials in general. This is what you will study in this first section.

There is a wide range of possible building materials available for our use and the performance of these materials has an impact on the cost, aesthetics and function of the building.

A well designed, economical building takes the following factors into account:

·  the properties and behaviour of building materials

·  the initial and long-term costs

·  the effects on the environment

·  how the materials interact with each other.

The traditional building materials such as stone, timber and clay have been used for centuries and the performance of these materials has changed little over time.

However, with the advent of modern manufacturing processes, the list of materials available to builders today is far longer than at any other time in the history of construction.

With the introduction of cement and concrete, steel, aluminium and products from the chemical industry, the traditional range has increased dramatically. Builders today must be aware of many factors affecting the use of these materials and how they have an affect on the environment.

Table 1, below, lists materials commonly used in residential construction. While not absolutely complete, it does illustrate the potential variety of materials available to us.

Material / Products and uses
Adhesives and joint-fillers / for gluing, sealing and filling cracks and joints
Cement / for concrete slabs and other elements; concrete blocks; cement render on walls; compressed cement sheets
Clay / for bricks and tiles; mud bricks; vitrified clay (sewer and stormwater) pipes
Cloth / canvas (for awnings etc)
Glass / for windows; skylights; doors; fibreglass insulation
Grasses / straw (in mud bricks and rammed earth walls and in bales in straw bale constructions)
Gypsum / for plaster on walls; grout between tiles; plasterboard
Metals / timber fasteners (such as nails, screws, bolts, brackets, gang-nail plates)
steel/iron (such as zincalume profile sheet steel, tanks, gutters, downpipes, wire and wire mesh)
steel (beams, columns, brackets and reinforcing)
copper (pipes and electrical wiring)
brass (taps, screws, door and window fittings)
aluminium (door and window frames, gutters, downpipes)
Paper / wallpaper; tar paper
Plastics / for electrical fittings; paints; wastes, water and sewerage pipes; plastic sheets (as moisture barriers)
Soil / rammed earth walls and floors
Stone / building blocks and slabs; slates; aggregate in concrete; pebble finish on concrete
Timber / floors; doors; window frames; weatherboards; roof framing; wall framing; shingles; shakes (similar to shingles, but split not sawn)

Table 1: Materials and their uses in residential construction

We will now look at most of the materials listed above.

Principal factors that affect the selection of materials

The selection of materials is affected by a range of factors including:

·  economic

·  physical

Let’s examine these factors in detail.

Economic factors
Energy content

Building materials are sometimes described as having a certain ‘energy content’. This refers to the cost of their production.

Stone (for concrete aggregate), timber or sand are materials having a ‘low energy content’; that is, they do not require a primary manufacturing process. Some materials, which are by-products of other industrial processes (eg wood particles, blast furnace slag and pulverised ash), also have a low energy content.

Materials with a low energy content are cheaper because energy has not been used in their production.

Other materials require energy in their production, and therefore have a ‘high energy content’. These include, for example, glass, bricks, plastics, metals and cement. This adds to their cost, and if local supplies of the raw materials are exhausted or unavailable, then purchase and transport costs are also added to the overall cost.

Labour and material costs

The initial cost of building will depend almost entirely on the costs of materials and on the labour costs. The cost breakdown for housing construction is roughly:

·  5% fee and charges

·  50% materials

·  45% labour

The choice of materials should not depend only on the purchase and installation cost, but also on the cost of repair, maintenance and replacement of short life-span products. Less durable materials may be cheap to buy but repair or replacement costs are usually high.

Cheap materials usually lower the value of a building, whereas more durable materials, such as stone and brick, mellow with age and give the structure a more aesthetic appearance.

Conservation of resources

Most world resources of metals, rainforest timber, fossil fuel and limestone are non-renewable and limited.

It is therefore important for us as consumers not only to be aware of those resources which are threatened or have bad effects on the environment, but also to use those which are, with management, safe both to our health and to the environment as a whole. Where possible we should use renewable resources, such as timber from re-planting programs.

It is also important that world fuel energy is not wasted by unnecessary processing and transportation. As well as being environmentally desirable, these savings mean cheaper materials.

Physical properties

Materials have different characteristics, or properties.

These properties are affected by physical, chemical and biological factors.

Here we will be looking at the following properties:

·  density and specific gravity

·  strength

·  electrical conductivity

·  thermal conductivity and capacity

·  moisture absorption

·  acoustics

Properties that relate specifically to certain building materials will be looked at in later sections where the particular building material is dealt with at length (eg optical properties will be dealt with in the section on glass).

Density and specific gravity

Different substances have different densities. Iron is much denser than aluminium which is why a piece of aluminium is much lighter than a piece of iron of the same size. Ice floats in water because the ice is less dense than the water. Density is measured by specific gravity.

Specific gravity is the ratio of the mass of a given volume of a liquid or solid to that of the same volume of water. The density of pure water is taken as 1 at 4° C.

Strength

A structure (eg a beam or a bridge) must be able to safely support its own weight plus the load it carries without distortion. Distortion will reduce the efficiency of the structure or make it break or look unattractive.

A structure can be made much stronger without increasing its weight, by being made in a different shape. Structures have greater strength when used in different ways. For example, in Figure 1 on the next page, the steel beam on the left (A) is much stronger than either of the other steel beams to its right (B or C), even though they all contain the same amount of steel.

Figure 1: Different types of steel sections

Some materials strongly resist being squashed. They are said to have compressive strength. Concrete, stone and brick are such materials. Other materials, such as steel, are strong under tension and will resist being stretched.

Concrete cracks easily when stretched. It has low tensile strength. The behaviour of concrete under pressure is illustrated in Figure 2.

Figure 2: The concrete beam cracks on the tension face (underside)

By using steel reinforcing in concrete, we combine the tensile strength of steel with the compressive strength of concrete, resulting in a product that is strong in tension as well as being strong in compression (refer to Figure 3).

Figure 3: Adding steel in the lower half of beam limits cracking

A piece of 25 mm wide galvanised steel strap, which is often used in bracing timber frames, is very difficult to stretch, but crumples easily when compressed lengthways. It has high tensile strength and low compressive strength.

Materials that are undergoing force are said to be stressed, and their change in shape is called strain. An elastic material is one which will recover its original shape when the stress is removed. A steel spring is elastic. A piece of chewing gum is not very elastic.

The response of materials to stress will depend on:

·  how stress is applied to them

·  whether the stress is continuous (eg a load-bearing arch)

·  whether the material is compressed, stretched or twisted

·  whether it is affected by moisture or temperature

Revision

Undertake the following Questions

1.  Why does ice float in water?

………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

2.  What are we measuring when we compare things with the density of pure water at 40C

……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

3.  What is the advantage in laying a timber beam across two end supports as compared to laying the same beam flat across the same supports?

………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

4.  Pair the following statements with the appropriate term:

a).  A material’s capacity to resist being squashed i) elasticity

b).  A materials capacity to resist being stretched ii) stress

c).  A material’s capacity to return to its own shape iii) tensile strength

d).  Force applied to a material iv) strain

e).  A change in material’s shape as a result of undergoing force v) compressive strength

5.  List & explain the three different types of stress that may affect the performance of a material?

……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

Moisture absorption

Some very porous materials will absorb moisture more readily than others. However, most materials may take up moisture from the air, from the ground (eg through poor dampcourses), from damaged roofs or gutters, or by condensation.

Condensation from moisture in the air will form on surfaces colder than the air. In the past, traditional building methods allowed water vapour to travel out of the building. Nowadays, however, condensation often becomes trapped on the inner surface of water-tight materials (eg flat-roof coverings, metal and glass wall-cladding, foil insulation). This can be prevented by the correct use of vapour barriers (materials which are designed to prevent surface condensation by being placed on the warm side of walls or ceilings in such a way that there is no gap in them).

Electrical conductivity

Materials that easily carry electricity through them are said to be conductors. Materials that do not are non-conductors. For example, most metals are good conductors and most plastics are not. This is why electrical wiring is copper and the protective sheathing is plastic.

Thermal conductivity and capacity

The thermal properties of a material are concerned with how a material reacts to changes in temperature. The thermal properties include heat expansion or contraction, insulation, heat storing ability, cooling, and reaction to frost, snow and ice.

Thermal conductivity is a measure of how fast heat travels through materials. This rate may be affected by density, temperature, porosity and moisture content.

For example, a building material that has a moisture content of 20% will lose two to three times more heat than when it is dry.

Thermal capacity is the ability of a substance to store heat. A brick or a stone wall, for example, will heat up slowly, hold the heat and lose it slowly as the outside temperature drops. A thin, light wall, on the other hand, heats and cools quickly and does not provide a buffer to the climate. Underground houses provide an ideal thermal situation because the surrounding soil slowly heats up during summer and is warmest in winter; it then gradually loses heat again so that, by summer, the soil temperature is cooler than the outside air.

The choice of materials of various thermal capacities will depend on the type of climate and the use to which the building is put.

Acoustics

Insulation from noise can be achieved by the use of dense materials, by avoiding openings directly onto noisy areas and by avoiding direct paths.

For example, a hall with a bend leading from a noisy machine shop to the workers’ tea room or a hall with lobbies or double doors would both reduce noise.

Some porous materials are used for modifying the acoustics in a room but sound can only be prevented from travelling from one space to another by the use of dense materials or a vacuum.