Budget Breakdown

What follows is a trade-by-trade analysis and build up of costs for a very basic four bedroom house, together with a note of the factors that could serve to increase them. Finance costs are not included as these will certainly be peculiar to each individual. Some other costs, such as those for carpets and landscaping, are included in order to give a proper comparison with a fully finished home and in order to bring the self-build project into line with the specification that most developers now follow. VAT is not generally included, except where it is nonrecoverable and is, therefore, a direct cost.

PRELIMINARIES AND ENABLING WORKS

If an architect is used rather than a local designer then the costs for the drawings may rise to around £6,000 or more if site supervision is required. This would be mitigated by the fact that engineer’s fees and SAP calculations would be included.

Service charges can vary considerably depending on the distance the supply has to come and the terrain it has to cross.

GROUNDWORKS

It is in the ground that most cost overruns tend to occur. This costing is based on a trenchfill foundation. If a deep strip foundation is used instead then the concrete costs would shrink, but the foundation blockwork costs would increase. Trenchfill gets you out of the ground in just one day and avoids any problems with weather or unstable trenches.

Deeper foundations cost more depending on the amount of spoil and concrete. Unstable ground might mean changing to a piled or raft foundation with add-on costs of between £4,000 and £8,000. Some groundworkers lay foundation blocks, others leave it to the bricklayers.

A solid concrete oversite could save £500 to £800, but beam and block floors provide a finite cost more acceptable to warranty providers.

BRICK AND BLOCKWORK/SUPERSTRUCTURE

Changes to a more expensive brick will affect the material costs but are unlikely to affect the labour or ancillary costs. Changes to a natural stone façade is likely to add considerably to the cost with the requirement for a backing block plus the extra cost of the stone. The labour is also likely to shoot through the roof as this is an expensive and increasingly rare skill and, taken together with the extra materials, you could be looking at between £7,000 and £10,000 extra. Changing to rendered blockwork might seem a cheaper option but in fact, because it involves two more trades – the plasterer and the decorator – and it also means that the scaffolding has to stay up longer, it could add £5 per square metre or close on £1,000. A timber first floor can save around £1,100. The decking and insulation is also around £600 cheaper than the insulated screed floor. Some bricklayers will undertake the beam and block first floor; others will prefer it to be done by the groundworkers coming back. PVCu windows are usually supplied and retrofitted by others. Timber joinery is fitted by the bricklayers as they go.

CARPENTRY

For between £1,500 and £2,000 the trusses could be changed to attic trusses, which would then allow occupation of the roof at a later date. Of all the elective extras, this is perhaps the most cost-effective. Internal doors, kitchen units and joinery can cost considerably more but may not actually add value to the home.

PLUMBING AND CENTRAL HEATING

Underfloor central heating could add around £1,600 to the initial outlay but running costs might be much better as condensing boilers work more efficiently at the lower temperatures that are required.

Most modern houses now have a mains pressure hot water system either using a standard boiler or a combi system. You can spend considerably more on sanitaryware but it might not be cost-effective as the ‘wow factor’ in bathrooms is often achieved with the accoutrements and accessories.

Rainwater goods are usually fixed by the plumber but can be carried out by another competent tradesperson. PVCu sections are undoubtedly the cheapest. The soakaways and their connecting drains are carried out by the groundworkers.

ROOFING

Handmade plain clay tiles in lieu of concrete interlocking, as costed, might add around £10,000. Even machine-made clay tiles would add about £4,000 and natural slates would add around the same. Breathable underlays might seem much more expensive than normal roofing felt but do not need additional ventilation to the roof void.

ELECTRICAL

It is all too easy to go over the top with this trade, doubling or even trebling the price. Think very carefully about your needs. Mark up the plan and then mark the walls before the tradesperson starts. It is usual for the self-builder’s light fittings to be fitted by the electrician.

PLASTERING & INSULATION

Plasterers can be supply and fix or labour only. Hard plastering costs roughly the same as dry-lining but takes considerably longer to dry out sufficiently for it to be decorated. With dry-lining, one is also less likely to experience cracking. Coving can add between £500 and £900 but is rapidly going out of style in favour of cleaner lines.

A plasterer might want a conveyor or hoist brought in for first floor screed, adding around £88. The insulation to a cold roof void can only be put up once the ceiling is tacked. It can be done by plasterers but is usually left to less skilled labour. Plasterers might not always want to lay the membrane and underfloor insulation.

CERAMIC TILER

Once again, this trade is often taken on by the self-builder. Professionals do, however, do it much quicker and much more neatly.

EXTERNAL WORKS

Savings can be made by swapping to a pea shingle driveway at around half the cost. Retaining walls can be very expensive. Keep all topsoil on site and as much subsoil as you need to make up levels. Remember, stacked soil shrinks to under half its volume. Sending soil away is expensive — buying it back is even more expensive!

DECORATION

This trade is often undertaken by the selfbuilder. However, the decorator is also responsible for ‘snagging’ many of the problems left by other trades and the maxim ‘prior preparation prevents poor performance’ are certainly the watchwords. It is one of the cheapest in terms of labour costs and day rates.

CARPETS

It has become the norm for developers to put in carpets and, therefore, to be properly finished, a self-build home should also include these costs. Carpet can vary from £7.50 per square metre up to £40 and even beyond.

GRAND TOTAL

Further reading:

• The Homebuilding & Renovating Build Cost Calculator
• How to Stick to Your Budget
• How to Cut Costs Without Sacrificing Quality