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Construction Technology an illustrated

Construction Technology an illustrated

One of the many reasons for writing this book was the need to introduce students to a level of detail which they would gain only with practical experience on site or in workshops.

Thomas Grant 3 years ago 0 85

Introduction

One of the many reasons for writing this book was the need to introduce students to a level of detail which they would gain only with practical experience on site or in workshops.

The accusation that the text includes too much ‘trade’ material could be levelled, but bearing in mind that many of the students who might use this text will be potential builders, quantity surveyors and building surveyors, then the inclusion of the trade material is very necessary. One of the primary functions of certainly the builders and quantity surveyors is the need to be able to assess the cost of any building operation. Unless they understand the processes to be gone through it is impossible for these professionals to give an accurate cost. They don’t have to be able to physically do the work but they must know exactly what is involved. So this text is for the ‘early learner’ who has no background in the construction industry. It is not intended to be an all embracing text; the physical size of the book could not allow that. So the author has been quite selective in what has been included, the reasoning behind the selection being the need to introduce the early learner to sufficient information to allow a general appreciation of the more common techniques used in domestic construction today.

Emphasis has been given to technical terms and terminology by having them printed in bold on at least the first occasion they are used.

Where these terms are generally confined to one part of the UK, some alternative forms are given as well. References to Building Regulations should be understood to mean all the Regulations which are used in England, Wales and Scotland at the time of writing. References to particular Regulations will have the suffixes (England and Wales) or (Scotland) appended.

Where the reference is to earlier editions of any particular Regulations, the date will be given, e.g. (1981).

A word about the drawings scattered through the text. None is to scale although, in the majority of instances, all component parts and components shown in any one drawing are in the correct proportion, with the exception of thin layers or membranes such as damp proof courses, felts, etc. which are exaggerated in thickness, following the convention in architectural drawing practice. Appendix J shows some of the conventional symbols used. The reader should get to know these; they are common currency when drawn information has to be read.

For the student who has recently left school there may be confusion, for the teaching of the use of centimetres in schools does not match up with the agreement by the construction industry to use only SI (Syst`eme International) units where only the millimetre, metre and kilometre are used to measure length. On architectural drawings dimensions are given only in millimetres and levels in metres to two places of decimals. Students will be expected to produce drawings in this manner during their courses. Following the convention on drawings etc., no mention of the unit of measurement will be made in the text when these are in millimetres. Any dimension given simply as a number must be assumed to be in millimetres. Any other measurements will have the unit of measurement following the number, e.g. 14.30 m meaning metres; 10 600 kN meaning kilonewtons and so on.

There are already hundreds of books on building construction or on just one aspect of it, be it a trade, material or technique(s).

There must be many more technical papers and leaflets and books produced by various organisations with an interest in the industry.

They include the Building Research Establishment (BRE), Construction Industry Research and Information Association (CIRIA), Timber Research and Development Association (TRADA), the British Standards Institution, all the trade and manufacturing associations – the list is endless, but those mentioned are reckoned to be the experts. So why has this author chosen not to quote them at every opportunity? Well, I have quoted bits of the British Standards where they were appropriate, but so much of the rest of the material is on a higher plane as to confuse the early learner in the art of construction. There is enough in here to get someone started on domestic construction as it is today. Get that correct and then go on to read the more esoteric material, especially when so much is about what has gone wrong in the past and how it was put right.

A couple of areas which are sorely neglected by too many students are:

Manufacturer’s literature – now widely available on the Internet Using their own eyes.

On the first point above, there was a time not so long ago when manufacturers tended to have their literature about a product prepared by graphic artists who knew diddleysquat about building and so perpetrated some real howlers and horrors, so much so that many lecturers had to tell students to ignore that source of information until they could sort out the good from the ugly. There were notable exceptions and many will remember the competition to get hands on a copy of British Gypsum’s White Book or the reception given to Redland’s award winning catalogue on roofing materials – goodness, was it that long ago? Nowadays catalogues have to be considered as a serious source of information and they come out faster than any other form of information and so become almost the only way to keep up to date.

On the second point above, what better way to see how a wash hand basin is installed than to get underneath it with a good torch and have a good look. Look into the attic with that torch, probe into all the corners and see how the roof is put together. Look at the doors and windows and how they interface with the walls and floors and the ceilings.

Experience in teaching the subject to school leavers has brought one difficulty to the fore which many students have – the inability to visualise. Test this for yourself – describe something to a friend and ask them to draw it as you speak. I’m sure you’ll get some funny results and some funny comments. It is a daunting task to be faced with technical construction drawings, especially detail drawings, and be expected to ‘see’ what is going on in terms of bricks, concrete in holes in the ground, joists and plasterboard, especially as you don’t know what these are in their raw state. Hence the inclusion in this book of photographs of bits and pieces and of construction. Fewer and fewer students get the opportunity to see a building site, mainly due to the safety aspects of a site visit and ever increasing insurance premiums. And yet seeing for themselves is what so many desperately require.

When starting this book a year or two back, the idea was to include a detail drawing alongside a photograph of what it looked like on site, hoping that this would in some small way make up for lack of on-site experience. While there are a lot of photographs, the result is not as good as had been hoped. The author could easily spend another year just getting the photography up to scratch and would certainly do things differently. For this text I was unable to find herringbone strutting anywhere close to me so I made a mock-up of a pair of joists and put in timber and steel strutting. It makes the point adequately when viewed alongside the details. So many other photographs could have been of that type had I realised the value of mock-ups earlier.

If you think the book lacks something or has too much of one thing, or is a bit of a curate’s egg or whatever, please write to me care of the publishers. If there is ever another edition it would be good – indeed vital – to have constructive feedback.

aac : autoclaved aerated concrete
ABS : acrylonitrile butadiene styrene
ach : air changes per hour
bj : black japanned
BM : benchmark
BMA : bronze metal antique
BOE : brick on edge
BRE : Building Research Establishment
BS : British Standard
BSI : British Standards Institution
CAAD : computer aided architectural design
CAD : computer aided design
CCU : consumer’s control unit
CH : central heating
CIRIA : Construction Industry Research and Information Association

cs : centres
csk : countersunk
CW : cold water
DLO : direct labour organisation
DPC : damp proof course
DPM : damp proof membrane
ELCB : earth leakage circuit breaker
EPDM : electronic position and distance measurement
EVA : ethyl vinyl acetate
FFL : finished floor level
FGL : finished ground level
FS : full sheet
galv. (hot dipped) galvanised
HBC : high breaking capacity
H&C : hot and cold
HRC high rupturing capacity
HW : hot water
IEE : Institution of Electrical Engineers
LH : left-hand
LPG : liquefied petroleum gas

MC : moisture content
MCB : miniature circuit breaker
MR : moisture resistant
m.s. mild steel
m&t : mortice and tenon
OPC : ordinary Portland cement
OS : Ordnance Survey
OSB : oriented strand board
PCC : pre-cast concrete
PFA : pulverised fuel ash
PS : pressed steel
PTFE : polytetrafluorethylene
PVA : polyvinyl acetate
RCCB : residual current circuit breaker
RH : right-hand
rh : round head
RSJ : rolled steel joist
RWP: rainwater pipe
SAA : satin anodised aluminium
SLC : safe loadbearing capacity
SS : stainless steel
SSHA : Scottish Special Housing Association
SVP : soil and ventilation pipe
S/w : softwood
SWVP : soil, waste and ventilation pipe
t& : tongue and groove
TC : tungsten carbide
TRADA : Timber Research and Development Association
TRV : thermostatic radiator valve
UB : universal beam
UV : ultraviolet
VCL : vapour control layer
WHB : wash-hand basin
WBP : water and boil proof
zp : zinc plated

Why should we be starting a book on building construction with a discussion of bricks and blocks? Quite simply because bricks are one of the major construction materials instantly associated with construction in the mind of the novice or lay person, but more importantly because the sizes chosen for the manufacture of bricks and blocks affect practically everything in a building except the thickness of the coats of paint or the coats of plaster. This will be discussed in more detail as we proceed.

Bricks and blocks are entirely ‘man-made’ masonry units. A variety of materials are quarried, mined or salvaged from manufacturing processes and made into bricks or blocks.

Stone is quarried and shaped but occurs naturally and was often used as it was found below cliffs or outcrops or on beaches, or from the general stones on or in the ground.

Artificial stone and reconstructed stone are ‘man-made’. Artificial stone is made by mixing particles of stone with a cement binder, water and occasionally a colouring material and then casting it into shapes. The idea is to create a ‘look’ of a particular kind of stone, even though none of that stone is used in the production. Reconstructed stone follows the same idea but generally omits the colouring agents since the stone particles used are the stone which is required at the end of the casting process. This is sometimes cheaper than the original stone and can sometimes be the only way to produce any quantity of something closely resembling the original stone where quarries are run down or closed. We will consider only bricks and blocks.

In Figure 1.1(a) there are two solid bricks on the left and two perforated bricks on the right.

In Figure 1.1(b) there are two single shallow frogged bricks. There is obviously need for explanation so we will start by looking at materials, sizes and shapes and so on:

  • Bricks and blocks can be made from a variety of materials other than fired clay or brick earth, e.g. calcium silicate and concretes.
  • Bricks and blocks can be obtained in a variety of sizes and types and kinds.
  • Bricks and blocks can be made in a variety of shapes other than the standard rectilinear shape discussed in this text but special shapes are the subject of British Standard 4729, Dimensions of bricks of special shapes and sizes.
  • Bricks and blocks can be cut into different shapes and these we will discuss later in the chapter.
  • Bricks and blocks standards and dimensions
    Bricks and blocks of fired clay are the subject of British Standard BS 3921 (see precis in ́Appendix L).
  • Brick is defined as a unit having all dimensions less than 337.5 × 225 × 112.5.
  • Block is defined as a unit having one or more dimensions greater than those of the largest possible brick.

BRICKS

Terminology

The surfaces of a brick have names: Top and bottom surfaces are beds Ends are headers or header faces Sides are stretchers or stretcher faces.

Bricks and blocks are made using mortar; they are not made in cement. Cement, usually a dry powder, may or may not be an ingredient in a mortar depending on the type of wall, its situation, etc. Mortars are mixed with water into a plastic mass just stiff enough to support any masonry unit pressed into them. This is an important and fundamental issue which is discussed in detail a little later in the chapter.

Brick sizes

Bricks are made in many sizes; however, we will use only one size in this text – the standard metric brick. A standard metric brick has coordinating dimensions of 225 × 112.5 × 75 mm and working dimensions of 215 ×102.5 × 65.

Why two sizes? The coordinating dimensions are a measure of the physical space taken up by a brick together with the mortar required on one bed, one header face and one stretcher face. The working dimensions are the sizes to which manufacturers will try to make the bricks. Methods of manufacture for many units and components are such that the final piece is not quite the size expected but it can fall within defined limits. This can be due to things like shrinkage or distortion when drying out, firing, etc.

The difference between the working and coordinating dimensions of a brick is 10 mm and this difference is taken up with the layer of mortar into which the bricks are pressed when laying. The working dimensions are also known as the nominal size of a brick.

Nominal sizing

The term nominal sizing is used to describe a size which is subject to slight variation during the manufacture of a component or unit. The variation – larger or smaller – allowed is generally given in a British Standard. The differences – plus and/or minus – can be different.

The slight variation in size of individual bricks is allowed for by pressing the brick into the mortar layer a greater or lesser amount but always using up to the coordinating dimen sion or space of 225 × 112.5 × 75.

Durability of bricks

Durability of bricks is very important when building in situations where freezing would be a problem and where the soluble salt content of the bricks would cause problems with the mortar – see sulphate attack later in the text. British Standard 3921 gives classifications of durability in terms of frost resistance and salt content, and an extract from the precis ́ of BS 3921 given in Appendix L of the book is given here:

Durability of brickwork depends on two factors which arise from the use of any particular brick: resistance to frost and the soluble salts content. Frost resistance falls into three classes: Frost resistant (F), Moderately

Frost Resistant (M) and Not Frost Resistant (O). Soluble salts content is classed as either Low (L) or Normal (N). So, one could have a brick which is frost resistant with normal soluble salt content and this would be clas- sified as FN. Similarly a brick which had no frost resistance and had low soluble salt content would be classed as OL.

Mortar joints

Mortar placed horizontally below or on top of a brick is called abed. Mortar placed vertically between bricks is called a perpend.

Coordinating sizes

The coordinating sizes allow the bricks to be built together in a number of different ways, illustrated in Figure 1.2. It is important to build brickwork to the correct coordinating size for the particular working size of brick specified.

Other components such as cills1, lintels2, door and window frames, etc. are manufactured to fit into openings whose size is calculated on the basis of whole or cut bricks displaced. This is illustrated in Figure 1.3.

If non-metric sizes of brick are to be used then the components built into the brickwork should coordinate with that size.

The height of the lintel is shown as three courses plus the joints between them mea- suring 3 × 65 + 2 × 10 = 215 mm.

The width of the window opening must be a multiple of half a brick plus the perpends, e.g. 8 × 102.5 + 9 × 10 = 880 mm.

The length of the lintel has to be the width of the opening plus the pieces which are built into the wall – the rests.

1 Cill: Alternative spelling, sill, is a unit or construction at the bottom of a window opening in a wall designed to deflect water running off a window away from the face of the wall below.

2 Lintel: A unit or construction over an opening in a wall designed to carry the loadings of the wall over the open-
ing.

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