Setting your budget

'Clients are sometimes cagey about money,' says Judith Tugman, 'but if you give your architect a budget, they can assess what's possible.' And discuss it as a team – your architect may even be able to do a job for less, in which case you could have more to spend on fittings.

A general rule of thumb is to allow £150 per sq ft of development, and remember you aren't just thinking about the extension, but the existing space inside, too.

If you opt for less expensive fixtures and fittings, you could squeeze this down to £100, but equally, if you go for higher quality this could rise to £200 per sq ft.

Bear in mind that, on top of the build budget, there will be architect, engineer and builders' fees, government VAT and building control and planning costs, too.

Don't forget to allow a contingency fund of 10 per cent for unforeseen circumstances.

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