Footings for internal wall - have I been blagged!

[tzartisan]

Hi. Had an extension done and have a few issues with the builder bill to sort out.

One thing I need an expert answer on so I know he is telling me the full story is about the need for footings.

We had a basic box one storey extension with a garage and a bedroom. He tells me the initial quote was low because he was going to build the double skin blockwork wall dividing the bedroom from the garage "off a slab"

Because we then had a door from the house into the garage that meant the garage floor had to be lower so he says that also meant the dividing wall also had to have a footing.

Wouldnt it be the case that the wall would have needed a footing anyway as it would carry the weight of the roof? He's not a bad bloke - I just want to know Im not being blinded with science! Ta

 

[Shytalkz]

If the wall was always required to support more than its own weight ie roof and floor perhaps, then it would most probably have required a footing from the outset, but there are several variables that could in principle allow it to take support from a slab. Not usually the done thing, though.

However, with the door in it and the consequent requirement to step down into the garage, it puts the issue beyond doubt that it does/did need a footing.

 

[^woody^]

If this wall had been planned to be built off the floor slab (which it could have done) then if the floor was lowered, why couldn't be built off the new floor slab (with a bit of thickening)- or am I missing something?

 

[Shytalkz]

You often do . God, I'm punchy tonight, spent too much time in the discussion forum winding up Softus and Joe-90 heheh.

It could, but it's a lot of ****ing about, far easier to wang a simple strip in. With anything other than self weight, the slab would need rebar in whether at the same level or stepped, to get the bearing pressure down enough for the sub base. 450 strip, wall, oversite, done. Far easier and no more costly.

 

[noseall]

we would install a strip footing every time in this scenario.

slab thickening coupled with a different floor level coupled with floor insulation = hassle.

 

[jeds]

It sounds reasonable to me. Building off a level slab it would have been relatively easy to thicken the slab for the dividing wall. (depends on the loads involved but let's assume these were calc'd and were OK) Once you lower the slab one side of the dividing wall, which is necessary to allow a doorway through to the garage, then thickening the slab becomes impractical and a strip foundation would have become necessary.