Extension foundations and slabs...
Discussion
It depends on the type of ground you've got. If it's clay which is affected by the influence of trees it's advisable to use a suspended floor unless you use a raft foundation, which is generally only acceptable when the amount of fill material/ made ground is less than 1.25m.
Another factor to consider is gassing. If there are levels of ground gas then a void and ventilation maybe required under the floor.
But yes, providing all the desired criteria can be met then a ground bearing slab is generally the most cost effective solution. Just chase the walls for services and come from above rather than below, unless you specify service ducts in the slab prior to being cast.
Another factor to consider is gassing. If there are levels of ground gas then a void and ventilation maybe required under the floor.
But yes, providing all the desired criteria can be met then a ground bearing slab is generally the most cost effective solution. Just chase the walls for services and come from above rather than below, unless you specify service ducts in the slab prior to being cast.
Edited by camp freddie on Tuesday 18th May 14:42
camp freddie said:
It depends on the type of ground you've got. If it's clay which is affected by the influence of trees it's advisable to use a suspended floor unless you use a raft foundation, which is generally only acceptable when the amount of fill material/ made ground is less than 1.25m.
Another factor to consider is gassing. If there are levels of ground gas then a void and ventilation maybe required under the floor.
But yes, providing all the desired criteria can be met then a ground bearing slab is generally the most cost effective solution. Just chase the walls for services and come from above rather than below, unless you specify service ducts in the slab prior to being cast.
Cheers Freddie!Another factor to consider is gassing. If there are levels of ground gas then a void and ventilation maybe required under the floor.
But yes, providing all the desired criteria can be met then a ground bearing slab is generally the most cost effective solution. Just chase the walls for services and come from above rather than below, unless you specify service ducts in the slab prior to being cast.
Edited by camp freddie on Tuesday 18th May 14:42
It's not clay and in London so Radon or similar to worry about. Shortly going to start getting the various bits of work tendered for which is very exciting - I've never done an extension before!
Generally speaking, raft foundations are not acceptable for extensions.
The ability to use a suspended timber floor rather depends on the relative floor and outside ground levels. You need a clear void below the floor joists and the oversite concrete should be at outside ground level. That, in effect, means you need the floor level to be some way above ground level.
Bear in mind as well that you may be enclosing a manhole cover by the extension, which in itself is not a problem as long as it has a bolt down double seal cover, but you need to make access provision through the suspended floor.
The ability to use a suspended timber floor rather depends on the relative floor and outside ground levels. You need a clear void below the floor joists and the oversite concrete should be at outside ground level. That, in effect, means you need the floor level to be some way above ground level.
Bear in mind as well that you may be enclosing a manhole cover by the extension, which in itself is not a problem as long as it has a bolt down double seal cover, but you need to make access provision through the suspended floor.
B17NNS said:
plug said:
You can also use concrete beam and block, with isulation and screed on top as a suspended floor.
what he said.Sarah, go on Homenuildi and renovation maagazine, they have printable cost calulated for the beam and block and comparitives. I assume you buy the mag...
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