Single storey workshop, good enough foundations

[moconnell]

Hi guys,
I am about to build a shed/workshop in my garden. I am sinking the structure down about a foot at the deepest (on a slight slope) so as to get best headroom as near neighbours (thus it is 2.5m high). I am planning to do knee high brick and concrete block dual walls with resting timber structure and pent sod roof. My question is since this won't need to pass buildings regs what's the minimum you think I should do for foundations that will actually be good. Don't really want to pay for half meter deep concrete really

 

[motorbiking]

150-200mm of fine compacted hardcore with a 100-150mm of concrete. The deeper the core the better, you might also want to find some metal or cable to reinforce the concrete. Also think about insulating the floor and or adding a dpc if you are planning to use the room in the winter month. If you have a cement mixer it doesn't take that long.. me and the mrs did this at 150 + 50 insulation + 100 top in 2 days over 2 weekends. It was approx 5 tonnes of concrete 5m x 4m

see pics
https://scontent-lhr3-1.xx.fbcdn.net/t31.0-8/11160688_1589078791359930_223414662200923578_o.jpg
I then built a timber frame
https://scontent-lhr3-1.xx.fbcdn.net/l/t31.0-8/11218564_1589078774693265_7563418439321441402_o.jpg
Insulated it with celotex
https://scontent-lhr3-1.xx.fbcdn.net/t31.0-8/11053547_1593978180869991_6259860349321107641_o.jpg
ended up like this:
https://scontent-lhr3-1.xx.fbcdn.net/t31.0-8/11952945_1636210776646731_1374386729866466210_o.jpg

 

[moconnell]

Cheers. OK I am just doing beneath the brick course as I am having a suspended wooden floor but hut will be otherwise very similar to yours. Nice job on that btw!

 

[motorbiking]

ahh right - I'd go down 600 min for the wall then - and of course you are aware that the room must not go any higher than 2.5M if you are close to the boundary.

 

[moconnell]

ok what rubble to concrete ratio if Igo down 600?

 

[motorbiking]

Is it going to be a retain wall? Do you need to think about waterproofing and drainage? - if it was me - I'd go 450 concrete on 150 compacted rubble, but it depends how firm it is when you get down to 450 or so.
e.g.

 

[moconnell]

ok I don't know I need to worry too much about water as I've dug the hole before winter and it never gets very wet but might be better safe than sorry I guess, but at least at one side it will be retaining as above.

 

[motorbiking]

Depending how you drain the roof water that might change. Could put your soakaway in now while you are at it.

 

[moconnell]

ha yes good point any idea if you could just soak away into a pond?

 

[motorbiking]

seriously ?

 

[moconnell]

that's a no isn't it?

 

[motorbiking]

Well the objective of a pond is to retain water and the objective of a soak away is to... well.. let the water soak away. depending how big your pond is, it will probably just end up flooding over. Depending on the pitch of the roof and size of the area, your soak away wont need to be massive.

A 1m³ soakaway will support a 40m² roof pitched at 20 degrees

 

[moconnell]

Got it Thanks a lot, very helpful indeed.