Concrete Floor Slab Movement

David.86

We've recently had an extension completed on our home, with all work signed off by the building inspector / building control at the district council.

It's about 9 months since the work was completed and we've noticed gaps appearing under the skirting boards in the extension and where the old building meets the extension, i.e. the new floor has dropped, currently at about 1cm drop. This has also moved kitchen units etc that sit on the floor and also attached to the wall

After doing some research and having the builder back out, it seems this is due to either movement of the soil, or compaction of the hardcore that the concrete floor slab sits on. All external walls are fine.

Our builder has advised going through our home insurance, however an exclusion states that loss/damage due to solid floor movement is not covered unless the external foundations are also affected.

So, what can we do?

Who is liable here?

We've paid a builder, we've paid building control and they've signed off all work to the required standard and we pay home insurance - yet it seems nothing is covering us for this damage and to correct it.

Help and advice would be much appreciated.

Thanks

dominoman

That really is worrying.

The builder is 100% liable. Compaction of the hardcore seems the most likely cause, but if it was properly compacted, layer by layer, that would not happen.

The builder will have to sort this out at his expense.

TheCyclingProgrammer

You will have to pursue the builder. They will likely have to claim against their own insurance (or pay directly from their own pocket but this sounds like it's going to be expensive).

Probably no harm in ringing your insurance company and seeing what they say though. You may need to use any legal cover you've got on your policy if the builder doesn't play ball.

Furts

A council should have a policy statement regarding Building Control inspections. To cover all bases check with yours, get this item (probably only a page of A4) and see if an inspection was required at foundations and also at oversite/dpm/dpc stage. Then get a copy of the inspection records to tally against this.

The builder is liable, but you need to see if the council are on your side - which will be useful. However if they were not called out for inspections, or the builder was negligent or fraudulent, there will be little they can do for you. Equally if they were negligent with their inspections that would open up a can of worms.

For example: Settlement of the fill material could be the problem, though not if you have a suspended floor. Or, the wrong floor type may have been built. Or, shrinkable clay and nearby trees could also be the problem. Nobody will be able to give a definite verdict without seeing your situation.

David.86

Thank you for your replies and advice.

Our builder has presently advised us to monitor the situation over a few month, with a view to removing kitchen fittings, amtico flooring etc and putting additional screed to build the floor level back up if the movement stops completely, then refitting everything. Or alternatively breaking the whole floor slab out, re-compacting the hardcore sub layers etc and pouring new concrete slab, then refitting everything.

He has advised that he has no such insurance to cover this (public liability only it seems) and all of his work was completed and signed off to building reg/control standards and that we would need to go through our home insurance - which it seems has a clause about not covering this type of issue.

I can't see the builder doing this out of his own pocket...

I'm going to look up on building control policy statements too.

Thanks,

David.86

The policy that I can find states this in regards to concrete floor slab-

"Casting of Concrete Oversite: when your builder is ready to concrete your floor slab we will visit to check that the ground has been properly prepared, that there is adequate floor insulation in place and that a suitable damp proof membrane has been provided."

TheCyclingProgrammer

Whether or not your builder has insurance has no bearing on his liability. If there is a defect in his work, it is his responsibility to rectify it at his cost and more fool him for not taking some form of indemnity insurance out to cover cockups like this.

Do you have legal cover with your home insurers? Have you spoken to them to see what they advise?

Furts

David.86 wrote: »

The policy that I can find states this in regards to concrete floor slab-

"Casting of Concrete Oversite: when your builder is ready to concrete your floor slab we will visit to check that the ground has been properly prepared, that there is adequate floor insulation in place and that a suitable damp proof membrane has been provided."

This is positive. The next point is did you call out the Inspector to do this Inspection? were you present when it occurred? and what was the outcome of it?

It will be very difficult to pin anything on the Inspector, but if this inspection was not undertaken, or the builder was covering up bad work, or the builder was acting fraudulently then you know where you stand.

It is the builders responsibility to put the work right. It will cost him a lot which is why there is not co-operation. Also be realistic - why should your house insurance pick up the bill for a builders negligence? This is simply not going to happen.

Court action may be the ultimate recourse, but try to negotiate first. Even if you go to Court you need to establish why the situation has occurred, and what should be done to rectify it. Whilst digging up the slab may sound like the answer it may cause the problem to re-appear when the new slab is laid. Here scenarios include shrinkable clay, water under the slab, the presence of trees, excessive fill depth, the wrong type of floor...these are some that come to mind.

cyclonebri1

David.86 wrote: »

We've recently had an extension completed on our home, with all work signed off by the building inspector / building control at the district council.

It's about 9 months since the work was completed and we've noticed gaps appearing under the skirting boards in the extension and where the old building meets the extension, i.e. the new floor has dropped, currently at about 1cm drop. This has also moved kitchen units etc that sit on the floor and also attached to the wall

After doing some research and having the builder back out, it seems this is due to either movement of the soil, or compaction of the hardcore that the concrete floor slab sits on. All external walls are fine.

Our builder has advised going through our home insurance, however an exclusion states that loss/damage due to solid floor movement is not covered unless the external foundations are also affected.

So, what can we do?

Who is liable here?

We've paid a builder, we've paid building control and they've signed off all work to the required standard and we pay home insurance - yet it seems nothing is covering us for this damage and to correct it.

Help and advice would be much appreciated.

Thanks

I fully get what everyone else has said, BUT, do you really want all this upheaval again?

What I'm saying is lodge the complaint with the builder, monitor further movement and act if if it gets worse.

10mm? it borders on normal settlement as all builders will claim (I actually think they are correct)

Furts

cyclonebri1 wrote: »

I fully get what everyone else has said, BUT, do you really want all this upheaval again?

What I'm saying is lodge the complaint with the builder, monitor further movement and act if if it gets worse.

10mm? it borders on normal settlement as all builders will claim (I actually think they are correct)

I have to cross swords with you over this one. On a concrete floor slab there will be no settlement visible to the consumer. Yes concrete shrinks, and yes, pre cast units have a camber, but when it comes to kitchen fitting stage the settlement and the shrinkage are long gone.

Any builder claiming 10mm settlement on a slab is OK should be accused of spouting BS.

phil24_7

I had a 4m x 9m, 200mm slab poured for my cellar and garage extension. There has been no noticeable movement in the slab despite the garage floor having the extra weight of block and beam with a 75mm screed and all of the cellar walls being concrete filled retaining walls.

If correctly installed they shouldn't move, they are designed not to.

I hate builders tolerances. I used to install lifts for a living and we used to work to tolerances of 1mm per 1m. Some lifts got very close to the lift shaft when builders work to tolerances of 10mm per 1m!