How Much Should My Foundations Cost?

21 February 2022
by L

Thanks for being here to support self builders.

We are in the midst of getting quotes for our build and the variation in figures are astonishing.
Could we get an objective opinion on the cost per sqm for 2m-deep trenchfill foundations?
One of the quotes is £500/sqm which doesn't sound right at all.

Many thanks for your help,

3 Answers

  1. Anamika Talwaria says:

    Hi Gwen,

    Thanks for your support and for your query. It’s a tricky one as much depends on your ground type and the specifics of your site, access etc.

    For reference, the Build It House had an 80sqm footprint and our ICF basement foundations came to £78,800 (or £985 per m2). As it was a basement, we gained a full storey of living space for that price.

    At Graven Hill, where we built, piled foundations are the most common option. We asked our groundworks contractors to quote for this solution at the time, and the would have come to around £48,000 (£600 per m2). Our team also quoted that trench fill foundations would have cost in the region of £28,000 (£250 per m2).

    Please bear in mind that these costs are around 3 years old, and there has been a considerable uplift in materials costs and inflation since then. Nevertheless, double that price does seem to be on the high side and it would be well worth investigating your options.

    Generally we would advise that you get a range of quotes in to sense-check the prices against each other.

    Best wishes,
    Anamika Talwaria (Build It Features Editor)

  2. Stephen Knapper says:

    Why are you measuring in cost per m2? Foundations are linear or cubic. Cost out at £12.00 per m3 of excavation, £35.00 per m3 of disposal and concrete fill at £130 per m3. This should get you in the right ball park. A groundwork company would add 15% to cover profit and overhead and then there is the dreaded VAT at 20%

  3. Chris says:

    Hi Gwen,

    Stephen’s correct that most groundworkers are likely to itemise their quotes in m3; but as you’re asking in m2 we’ve replied on the same basis. Using per m2 rates is a common way for self builders to understand and compare figures.

    Do make sure you’re comparing apples with apples for m2 prices… so, is this on a gross internal area (GIA) basis or gross external area (GEA)? GEA will be larger than GIA, so this can skew per m2 rates.

    Assuming this is a new build house, then VAT shouldn’t be charged on labour for foundations as this work is zero-rated, and you should be able to claim back the VAT on materials. If it’s an extension, VAT will be charged at 20%.

    Best of luck with your project!

    Chris (editor, Build It)

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