|On 9 Feb 2006 08:47:33 -0800 Bigbrian wrote : |> The guy doing the digging said they normally |> have to go about 1 metre, but he always keeps going until he hits |> something strong enough to build on. | |I had one of those in my BCO days on Kingston Hill: phone rings |"we've gone down ten foot and still haven't hit clay". Well up |there you wouldn't - going down 2'6" on to the sand and ballast is |fine.
I was in this position when building an extension. We are on made up land, and there was loose shale in the bottom of the foundation trench. The BCO said "You can keep on digging till you hit the original ground surface or install a reinforced raft" I looked around and decided that the original ground was probably 20-30 ft below the bottom of the trench, so I went for a reinforced concrete raft. The extent ion is firm as a rock after 25 years.