Foundation for new extension.

[dubman]

Hi, I have a couple of questions about a friend's new extension:
1: If a foundation for a 1-floor (aprox 12 square meters) extension was incorrectly laid, using only concrete (no mesh reinforcement) would it be possible to correct the problem by later digging down (after the extension has been built) and laying concrete and iron mesh reinforcement in overlapping sections?

2, Provided that there is the correct reinforced concrete foundation under the main walls, would that be sufficient, or does the reinforced concrete have to be under the entire floor area? Thanks you..

 

[noseall]

What leads you to think the floor needs digging up and replacing with a reinforced concrete slab.

This can be done so long as the floor was laid independently of the walls.

 

[^woody^]

Concrete foundations do not normally need reinforcing

 

[dubman]

Ok, so in the case that only concrete (no iron mesh) was used under walls as well, would that be sufficient? I mean not to use any iron mesh reinforcement in the foundation at all? Or would it be possible or recommended to dig down and lay the new concrete and mesh overlapping sections? Thanks

 

[^woody^]

If this is in Spain, then you really should do whatever local regulations require.

Generally though, foundations for walls would not require reinforcing unless there will be some abnormal ground movement which may try and push up on part of the foundation, or if point loads may push down

For slabs, (ie building walls off floors) reinforcing may be good to help deal with a wall pushing down on the slab at one point. The alternative would be really thick slabs or thickening slabs where any wall will be built

Without knowing the details of the design then its hard to comment, but any comment would be in the context of UK construction and ground conditions

 

[dubman]

Ok, actually I'm in Spain, but the house in question is in Ireland. I'm not fully sure either of all the details of the build, so I was asking some general questions. Personally, I would prefer to use mesh reinforcement in any kind of foundations. Thanks I really appreciate the help.