Originally Posted by
Thai Dhupp
Hi Shutee, welcome and thanks for your input and interest...
OK.... it depends on the strength and ability of the land to support the load (ie the house) and the size of the house you are building (and engineers will tell me to mention point loading, bearing friction, etc etc!!)
In our case we took advice from the OrBorTor office. The top layer of ground looks firm but when wet it becomes springy, soft, and slippery i.e not so good. We built up the land in any case with another 1m of as dug material but it was no better than the original layer. Below that however is a much stronger and solid strata and thats what we wanted to get down to.
Often when you see small slab supports in the soil and a ring beam, it is a single story dwelling, ie much lighter. Someone will have done that calculation for the point loading and the strength of the soil and determined how many uprights are needed. As you say, the ring (plinth) beam and slab ties it all together. Its a sort of raft foundation, spreading the load so as nothing sinks.
Our 'dwelling' , when finished will have 2 stories and a substantial roof, with a footprint of 256m3. its being built in 2 stages - zone A and B now and zone C when funds allow (!).
So .. we have to pile. Now as to why we went with drill and cast. Simple really... K.Pot (builder) had all the equipment to drill and cast, could make super cages for the drill holes and gave a very good price to do it. Either method would have been Ok; we went with him as he has total control and it's in his interest to do a good job as the house he is then building rests on his pile work.