Groundwork & Foundations

What kind of foundation for a trapezoid lean to shed?

Anonymous user 28/02/2024 - 3.51 PM

Hello, I have a decent size space next to my house that I want to build a shed in, however its not square but a trapezoid shape. The dimensions are 5.8 metres at the straight side (next to my house), 1.2 metres at the narrowest part at the back (before reaching a fence), 6.1 metres at the angled side (which runs parallell with another fence) and 2.3m at the front, the widest part. The main issues I am concerned with are: 1.The soil beneath is full of clay. 2. I am unsure of how to make the foundations so: A) They don't subside or crack B) The trapezoid shape maintains its strength (as it goes from narrow to wide) C) The lean will be attached to house brick work and dont want any subsidance to pull out roof and wall fixings and damage brickwork. There is also a very tall black poplar tree 10 metres away, but from digging today it doesn't seem like its roots are an issue. My initial plan was to: • Put down 100mm compacted hardcore base • Create slab formwork • Add a 12mm thick expansion strip so it sits between house and concrete slab • Add rebar mesh cut to size on concrete castles • Add 100mm thick concrete slab on top • Then After a few hours cut a relief line 1 inch deep halfway through on the length I was fairly happy with this but after digging today and seeing how much clay is in the soil I have some concern and not sure how it will hold up with the changing seasons. The heaviest single item that is going to sit on it is a 210L water butt So my main question is with these factors taken into consideration how could I make the foundations without worrying for any subsidance/ cracking in the future.... or is my plan adequate? Many Thanks, Antony