Understanding costs, establishing a budget, and calculating your cashflow are among the most important steps before commencing a self build or renovation project.

To establish your cashflow (money out and money in), you’ll need to know your project schedule and the costs incurred for each stage. Before you even start the building work you will have costs, such as legal fees, site surveys, planning and Building Regulation fees, site insurance and structural warranty premiums, and potentially a stamp duty fee. So always include these factors in your overall cost plans. You should also include a 10 – 15% contingency within your budget, for any unforeseen issues.

Your plot will probably be around 40% of your total project budget, leaving 60% for the construction phase itself. As a general guide, your build budget costs breakdown should look like this:

20% – preliminary costs, groundworks and foundations
13% – wallplate level
22% – wind & watertight
12% – 1st fix
33% – 2nd fix to completition

In terms of finance options, self-build mortgages are specifically designed so that funds are released for the purchase of the land, and then given out at various stages throughout the project. Firstly, the lender will agree an overall amount that they are prepared to lend towards the land and the build. Next, to establish the size of each stage payment the lender will need to approve your costings and cashflow, and will then agree the stage payments based on the key stages of your project, as above.

An important consideration is when these funds will be released in relation to your build stages. It may be in advance of each stage, in arrears, or after each stage has been completed. It will all depend on your cashflow requirements. 



An advance self mortgage, available exclusively through Buildstore, lends up to 85% for the land, and up to 85% of the build costs. Funds are released ahead of each build stage, and are based on the actual costs in your budget – this means that the required funds will be available in your account for each stage. It may also be possible to re-adjust the spread of your budget if you find that you’ve over or underestimated a certain stage, so long as the overall cost of works remains the same.