U&M Group

Can You Build a House Without a Foundation?

Wednesday, June 19th, 2019 AT 03:55PM

We assume that any building needs a foundation. It’s so obvious that we use it widely as a metaphor — the foundation of arguments, beliefs, organisations and so on. The foundation is what makes anything safe and secure.

So can you really build a house without a foundation?

What Is the Foundation For?

The simple answer is that of course, you can — as long as you don’t need it to stand for long. Historically, houses without foundations have tended to be simple affairs, built around an earth floor, which weren’t designed to last.

Although a building may be able to support the downward thrust of its load without a foundation, it’s the sideways motion that creates the problem. As the ground changes temperature with the seasons, it expands and contracts, causing instabilities that make the building lurch.

This means that, unless it’s built on a rock so solid that there’s no variation, stability depends on having the structure’s base resting on a level deep enough to maintain a constant temperature. This should ensure that lateral movement is kept to a minimum.

Are There Houses Without Foundations?

Substantial buildings have been successfully constructed without what might be thought adequate foundations. Perhaps the best known is Salisbury Cathedral, built on marshy ground, which supports a spire on foundations of just four feet depth. This can be achieved by building on a “raft” in soft ground, which acts in a similar way to traditional foundations, but it’s not an easy technique to get right.

Other types of buildings that can be created without foundations are those built on piles or stilts. This usually happens on flood plains or marshy coastal areas, but these homes do actually have foundations, if not traditional ones. Here, the weight is distributed down through the piles to a stable level, essentially doing the same job as a more standard foundation, with the added load capacity created by ‘skin friction’.

What If My Home Doesn’t Have Adequate Foundations?

Although you’re unlikely to have a home today without any support, some older houses were built with shallow foundations. Other houses may have had what seemed adequate foundations, but subsidence or other movement has weakened them.

In these cases, the foundations of an existing building can be extended down to a more stable level. This is known as underpinning and can be done either by excavating below the existing foundations or by sinking piles to transfer the weight to a safe level.

If you have any concerns about whether the foundations of your home are adequate to support its weight, you’re very welcome to get in touch with us.