Calculating your Build Costs

A simple cost estimating guide for people building their own home

Discover how much it will cost to build your own home with our monthly build cost calculator

one of the most important aspects when planning your self-build or home renovation/extension project is working out how much it is going to cost. This figure will depend on the size and shape of the house, the level of your own involvement, where in the country you intend to build, and the materials you’re going to use. If you can make even rough decisions about these factors, then you can begin to work out how much it is going to cost.

As a very general rule of thumb, expect a building plot to cost between a third and a half of the end value of the finished house. The costs of building a house will then depend on the variables listed above. All building work is usually quoted on a cost/ m2 basis. For example, a typical new four bedroom self-built home is around 200m2 (with 100m2 on two storeys) and usually varies between £1,000-£2,000/m2 (although self-builders can achieve costs of between £300-£3,500/m2).

Renovation costs are more difficult to establish as they involve many variables, but allow at least £1,000-£1,500/m2 for work. This, added to the cost of the plot/house and with a 10-30% contingency, should result in less than the final end value of the house.

The table below, based on information from the Building Cost Information Service (part of RICS, the Royal Institution of Chartered Surveyors), is updated monthly to help you work out a more accurate estimate (note that these figures are for build costs only and do not account for VAT, which is not charged for self-build projects).

There is a free online version at homebuilding.co.uk/ calculator.