The Foundations cost guide says that it is important to get a soil investigation and engineer’s report.

We are buying a 50-year-old house with normal foundations, demolishing it, removing the foundations, then building a larger house on the plot. Would you still recommend getting a soil investigation and engineer’s report?

  • Mark Brinkley

    If the existing house shows no sign of any ground movement, then that’s a pretty reliable indication that you are not going to suffer from ground movement issues in the future. Have you inspected it? Are there tell-tale signs of movement? Cracks in the walls either external or internal?

    Having said that, there may be other factors at play. The presence of large trees that may not have been there 50 years ago can have a dramatic effect on ground conditions, as can leaking drains. So just because the existing house is sound, it doesn’t follow that a new one will be. There is no compulsion to have a ground survey and indeed surveyors are often so risk averse these days that they will recommend piling to protect themselves as much as your foundations.

    The risk is that if you don’t have a ground survey and then start the excavations, you might have to go very much deeper that anticipated, adding greatly to costs, as you will then be working to the judgement of your building inspector and/or warranty provider.

  • Daniel Price

    I agree with Mark, this is all about risk. If your intention is to replace your existing property with a larger one then I presume you will be imparting different (increased) loads on the soil beneath which may behave differently to how it has done in the past. A few basic engineering tests on soil samples gathered during an investigation, performed by a qualified and quality ground investigation company/engineer can help allay any fears of potential settlement and/or adverse reaction to building loads and help you design cost effective foundations.

    The cost differential between a piled foundation solution and simply more robust shallow foundations could be significant depending on the quality and depth of suitable bearing strata.

    The term "unforseen ground conditions" is something often pointed to when larger construction projects run amiss due to poor soil conditions so I would err on the side of caution myself.

  • David Hughes

    Thank you both for your advice. I will arrange the investigations.

  • Post a comment
    You must be logged in to comment. Log in