I live in a new property where due to the underlying characteristics of the land, piling was required for the foundations.

Due to the additional cost, I'd like to explore what options for extension or conservatory I might have that do not require additional piling.

Does anyone know if there are regs relating to size, load or construction that might determine whether I have to pile or not?


  • You've left out far too many factors to even hazard a guess. – jwh20 Jul 5 '20 at 17:27

The Code says the foundation need to be “adequate” for all loads.

Most people think of vertical loads, but there are horizontal loads, freeze/thaw loads, etc.

I too live where the ground is mush. Usually we install piling, caissons, etc. However, in certain situations we install a “floating slab”.

This system is a structural slab (with reinforcing steel) with edges that turn down about 12” at the edges. (We don’t have a frost freeze/thaw issue here. If you do, you may want to extend it somewhat.) We install about double the amount of reinforcing steel than we use in stem walls.

We use this system for small, simple, fairly symmetrical buildings...which sounds like your project.

You’ll have one additional issue of where it connects into your existing house. Because your house is on piling, it will not move (settle) over time. Therefore, I’d recommend the structure be a few feet from your existing house where you can plan for a few inches of settlement. The connection space between the two structures can fasten (rest on) on both structures and flex when the conservatory settles slightly.

In fact, installing augured piling, hammered piling, etc. next to your home may cause significant damage (cracking plaster, cracking windows, etc.)

Any plumbing or electrical supply lines should have blockouts through the slab so it’s flexible.

Because of all that glass in your conservatory and you don’t want any differential settlement in the walls, I’d recommend you design the perimeter foundation as a concrete beam. You’ll probably need an architect or structural engineer (not a civil engineer) to help you.

  • Lee Sam, thanks for the answer. There are clearly many factors involved and much to look into with the help of a structural engineer, but at least the details you've offered give me the confidence to pursue it. If the answer had been that if the house is piled, then you'll need to pile, then I might be deterred from doing the project. Thanks again. – Mardymonkey Jul 5 '20 at 20:41
  • Remember, all buildings settle. Just make sure it settles uniformly and allow for a little compared to your existing structure. – Lee Sam Jul 5 '20 at 21:56

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.