Metal Raft

[jtaunton]

I have been told that my house is built on a metal raft, as it is above a coal mine. What does this mean ? Do I have foundations ? Does it mean I can't subside because the whole house would move at the same time ? What if I ever wanted to extend - do I need to extend the raft ?

Any answers much appreciated....

 

[Thermo]

normally a house is built on strip foundations which spread the load from the walls of the house onto strips of the ground underneath. This means that certain areas of the ground under the house are under enourmous load compared to areas that are not (ie not under the strip foundations. If there was any sort of subsidence under the house due to old mine workings this could be enough to bring the lot down. The metal raft is basically one big foundation which spreads the load across the whole of the area of the house and evens it out and lessens it, making any collapse less likely. You could still subside if the hole was big enough and it would take the whole house! Basically if you think of standing on some ice and your feet as the strip foundations, they are carrying all the load and thus exerting more pressure on the ice at that point. If you lay across the ice you spread the load and are less likely to fall through. Same principle! I guess if you extend it will need similar foundations.

Hope that makes sense!

 

[jtaunton]

thanking you....