Beginner's Guide - Step 2

Using Roof Space:

Using roof space to provide accom moda tion is less expensive than adding a full extra storey. For estimating purposes, calculate the cost separately by multiplying the additional useable gross floor area by 70% of the average £/m2 for the house.

Basements:

For estimating purposes, treat basements as above-ground space and include them as part of your measurement of gross internal floor area.

Facing Materials:

Alternative facing materials will have a direct influence on overall build costs. To adjust for this you need to add or subtract an allowance/m2 for your chosen wall cladding from the sum allowed for cladding within your chosen specification. For render on blockwork allow £25/m2; for timber cladding allow £25/m2; for hand made weather tiling allow £54/m2; for rubble walling/flint allow £90/m2; for reconstituted stone allow £48/m2; for natural stone allow £75/m2.

Roofing Materials:

Alternative materials will affect your over all build costs. To adjust for this, add or subtract an allowance/m2 for your material from the figure allowed in your chosen level of Build Quality (e.g. £28/m2, £36/m2 or £45/m2). For new Welsh slate allow £60/m2; for secondhand slates allow £35/m2; for handmade clay tiles allow £65/m2; for reed thatch allow £80/m2.

Sloping Sites:

For estimating purposes, allow an additional £10/m2 for every degree of slope, e.g. for a 5° slope, add approximately £50/m2.

Bespoke Joinery/Kitchen:

To adjust for bespoke handmade windows and doors, or a kitchen, add the quote (excl VAT) to your estim ated build cost, less the allowance of £40/m2 already in the costs.

Ceiling Heights:

For every 0.1m of additional ceiling height (on top of the standard 2.4m) add 1% to your £/m2.

Garages and Outbuildings:

Although an integral garage is unlikely to be completed to the same standard of finish as the rest of the property, for cost esti mation purposes include the area of integral garages within your mea surements of the gross internal living area.

To estimate your total project costs you also need to take into account all other costs, e.g. plot, professional fees etc. Calculate these and add the total to your build cost estimate.

Further reading:

• Beginner's Guide: Introduction
• Beginner's Guide: Step One
• Beginner's Guide: Step Three
• Beginner's Guide : Self Build Schedule
• Beginner's Guide: Tax
• Beginner's Guide: Finance