foundations, and ground bearing slab.

[Big Jimbo]

Evening all. I have spent a few hours on the Labc foundation depth calculator today, and if i want to do strip founds, i range from about 2mt deep to 1.5mt . I am told by a builder who has just built 3 houses very near me that i am on good ground. He went 1mt deep, but i have trees, hence why mine need to be deeper.

I know that going deeper than 1.5mt will mean that i will need heave protection to the inside of the trenches.

Because i have a fair few old buildings to take down, i wanted my floor to be a ground bearing slab, ie; old building rubble 150mm min. 50mm sand, dpm, cast concrete 150mm. insulation and screed.

I think i have read somewhere ? that if my founds are deeper than 1.5mt, than i cant have a ground bearing slab as my floor. Anybody have any idea if that is right ? If it's to do with heave, could i not compensate by having a layer of heave protection on top of my sand ? and if necessary putting some re-enforcing in my 150mm layer of concrete ?

Still waiting for my engineer to come back to me.

Thanks in advance.

[Oz07]

Not usually accepted on deeper founds. Might be best off excavating an concrete before deciding on slab/floor. Bco might only make you go 1.5

[nod]

Ours where pretty similar to yours 

1.5 to 2000 Good ground surrounded by Ash and oak trees 

I used clay board to help with the heave Engineer specified BB

However I built two D garages 

Same foundations BC was ok with me using a slab foundations for these He specified 25 mil insulation around the perimeter to keep the concrete off the walls