A method of comparing house costs

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Publisher’s version / Version de l'éditeur:

Technical Note (National Research Council of Canada. Division of Building Research), 1956-03-01

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Ball, W. H.

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DIVISION OF BUILDING RESEARCH

TEClHINlICAL

NOTlE

208

NOT FOR PUBLICATION

PREPARED BY W.H. Ball CHECKED BY

FOR INTERNAL USE

APPROVED BY R.F .L. PREPARfD FOR Discussion of House Costs ｾｍ｡ｲ｣ｨ 1956

SUBJECT _{A METHOD OF COMPARING HOUSE COSTS}

Experience has shown that there is need for a method of comparing house costs which is flexible in its ｡ｰｰｬｩ｣ｾｾｩｯｮ arid which will lend itself to wide areas of use so that local factors

such as climate, custom, methods, and material and equipment use, may not make comparisons difficult. A simple method of comparing the cost of building components and services would, in ｾ､､ｩｴｩｯｮＬ be most useful in _{establishing the economic value}

of various materials and techniques.

A distinction may be usefully made at this time to

emphasize that this note is not intended to discuss the various methods of determining house costs; rather it is intended that only the presentation of the breakdown of costs should be

discussed. Once the method of presentation has been established, the methods of cost estimation can then be adjusted to suit the requirements of presentation.

For the purpose of presentation of costs a house may be broken down into two major components: the structure and the building services. It is not qUite this simple in practice as

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the structure must accommodate the service elements and it is therefore affected by them. It is suggested, however, that such a subdivision is practical for general purposes. It is also suggested that such a subdivision of costs should increase the usefulness of the summary of costs, as the services provided in "a house are generally dependent on such factors as the

availa-?ility of services, living standards, and climate. Thus it may be possible by such a separation to make cost comparisons of basic structures between areas where there are appreciable differences in the services provided. Service installations are usually provided by specialist trades in most areas and this lends additional convenience to this subdivision.

The House Structure

The breakdown of the house structure into components that are capable of a measure of universal comparison with

respect to cost is a more difficult task. Although most houses have foundations, floors, walls, roofs and partitions, the

proportions of such elements vary with the type of house and therefore over-all comparisons between houses of different shape and design may be difficult. For example, it may not be

•

appropriate to compare a single-storey house with a multiple-storey house. However, the comparison of costs in this way will provide useful information as to the relative costs of various components in houses of various forms, and it would not be unreasonable to confine cost comparisons to houses of

similar form when other than relative cost comparison is desired.

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Building Services

A comparison of the cost of services also has its complications because of the degree of refinement possible in any of the services. However, the lines between the different services are generally clear cut, and there should be little 'difficulty in provLing a reasonable comparison in any case.

Proposed Breakdown for Cost Comparison Purposes

I

-

i -

-I,

-

I

-

-I

-

,

-

I, I

I

$

100%

I

I , I Crt % of cost I

i

of services

I

-

I

-

--

-

--

I

-

-1

i

$

_I

100% 100%

I

Column A Column B

Cost

%

of cost

%

of cost

$

of structure of house ,

-

_I I I

I

I I 5 Partitions 1 Excavation, foundations and backfill 3 Enclosing walls 4 Roof

2 Floors above foundation

walls including I

columns and basement

I

Structure beams !

-6

Heating or cooling Services

7

Plumbing

8 Electrical

The subdivisiOn proposed in Column A may be used for comparison between areas where there is a wide variation between

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services normally provided. Column B could be usefully applied in anyone area where there is a reasonaly uniform practice in both the structure and services.

The proposal has been made as simple as possible, and ,as a result may be criticized as it may involve the breakdown of

costs of elements to a degree which may suggest difficulty in accounting for labour and materials actually used on the job. For example, the apportioning of costs of plastering to

enclosing walls, ceilings under roofs, and partitions may be

difficult. Simila.rly a breakdown of the cost of the .,installation of millwork, which is generally stated in a lump sum, may be

difficult to apportion to the various major components. While these difficulties are foreseen their effect is probably related to the custom of estimating on the basis of trades and bulk

material quantities rather than on the basis of a quantity survey of the various operations and components in a house.

The multitude of operations involved in the construction of a house suggest that an error in calculating the cost of a few minor components will introduce no serious error in the estimation of the cost of major components or the whole house.

It will be noted tha.t no provision has been made for builders' overhead and profit. For research purposes the main requirement is to know the effect on the cost of a component or service of either materials or the technique of erection. There would therefore be little advantage in masking the true figures with the inclusion of a profit item.