How much?

Published: Wednesday, August 31, 2011

This will be based on available savings, the likely profit from the sale of your existing home and what you can expect to raise on a mortgage.  Traditionally, around a third of the total has been spent on buying a plot with the remainder on construction.  Today, 40-60 per cent is more likely to be spent on the plot and in popular areas this percentage can be even higher.

Estimating the build cost will depend on the size, construction, complexity, materials, local labour rates and the specific conditions of the site such as poor ground conditions which demand specialist foundations.
In other words, it’s complicated and you’re almost certain to require specialist help.

Architects and builders’ price books, detailing the costs of every aspect of construction and updated annually, are available in local libraries (look for names like Spon or Wessex). For a more down to earth approach, try Mark Brinkley’s Housebuilder’s Bible.

Estimating software such as EstimatorXpress from HBXL is a good way to plan the cost of your project.  Just input your project’s dimensions to calculate the cost, and because it’s linked directly to a builder’s merchant’s price list, the estimates are accurate.  Design and build package companies also provide basic costings for their standard designs.  Some builder’s merchants will supply free estimating services based on house plans.  Quantity surveyors can also provide estimates, though they’re unlikely to be cost effective for a single house.

Arriving at a precise budget will depend on negotiations with your designer or project manager and your contractor.  Don’t expect to tie everything down before you start.  Every build has its own peculiarities.  A 10 per cent contingency fund is recommended.