Pouring a concrete base, up against a drop

PeteW

Hi, I'm looking to build a garden office at the bottom of my garden on what used to be a vegetable patch. As such, I was looking to lay a concrete slab as a base. Where my build differs to those I've seen elsewhere is that the area I want to build on has a drainage ditch directly next to it.

See photo of site: https://imgur.com/XQFtg9X

And a rough drawing of what I want to end up with: https://imgur.com/S9MECCa

Currently the soil is retained by some concrete slabs embedded vertically and some wood as you can see in the photo.

Any suggestions on what I would need to do to reinforce the area where the soil under my base meets the ditch, to ensure the base is stable.

My assumption is that if I don't reinforce it at all, the weight of the base and the building could potentially cause some sort of subsidence as the soil is effectively squeezed out to the side.

Thanks

Pete

spadoosh

Have you looked at pier foundations rather than slab? Im not slightly proficient in foundations but i understand theyre usually more suitable on uneven ground.

stuart45

What is the construction of the office going to be eg timber, cavity wall masonry etc?.
What size will it be?

PeteW

stuart45 wrote: »

What is the construction of the office going to be eg timber, cavity wall masonry etc?.
What size will it be?

Timber framed and clad. Approx 4.4 x 3.7m, 2.5m high with monopitched roof, glass bifolding doors at front, large uPVC window on one side.

stuart45

How close to the edge of the ditch is it going to be?

PeteW

stuart45 wrote: »

How close to the edge of the ditch is it going to be?

Not sure yet. As close as it can be, ideally.

stuart45

Obviously an on site inspection is needed, but if you google ' angle of repose' you will find that a building normally puts pressure on the subsoil at an angle of 45% from the base of the foundation.
A raft foundation allows for some movement of the building, or a retaining wall built as part of the foundation are possible.
It depends on how much you want to spend. At least a timber framed building is lighter and allows for some movement.