Foundations for tricky sites

From troublesome trees to stubborn soils, a whole host of problems can make the early stages of your project dificult to navigate – but they can be solved

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Getting out of the ground is one of great unknowns of self building. The fact is, you can never be entirely certain what lies below the surface before you’ve dug the foundation trenches – and if any problems are going to affect your project, they’re likely to happen at this stage. The good news is that most of these issues are surmountable; and if you can identify them in advance, you should be able to solve them relatively cost-effectively.

Common plot challenges

Given their buying power and political clout, the major housebuilders tend to have first pick of the plots. They’re keen, unsurprisingly, to skim off the choicest examples – namely the level, easy-to-develop sites that, as far as they can identify, aren’t likely to fall foul of planning or practical issues.

This could change with the advent of the Right to Build (see page 62 for more on this) but for the time being, the status quo remains and self builders tend to get second dibs. That’s not to say there aren’t great sites out there – and indeed many developers won’t even consider sites of the size that might only support a single bespoke home. What’s more, some plot features that a big developer might label as problems may actually offer interesting opportunities for self builders.

Your site might present a variety of issues that could impact on your foundation design. These range from steep gradients through to poor or infilled ground, the presence of trees and issues with service connections – to name but a few. The good news is that, in most cases, these headaches can be fairly easily and cost-effectively navigated, especially if they’re identified early on in the planning process. Here’s a quick guide to how some of these scenarios could affect your scheme:

1 Trees

The presence of mature trees on a site can be a double-edged sword. They can add character and value to the finished property – but some specimens may hamper your building plans. The roots don’t pose a direct threat to buildings; it’s the tree’s thirst for water that’s the issue. This can significantly affect the soil’s moisture content, causing shrinkage or swelling (known in the trade as heave). So what do you need to bear in mind?