Help! - Major cracks in concrete floor

[grahamw]

Hello all,

My house is around 7years old and I have just lifted the carpets , ready to put down laminate, in lounge and found a number of cracks in the concrete floor. After further investigation I have found that these run the full width of the house.

The worse of the cracks is around 1inch across and 4-5inches deep (all the way to DPC) and it seems to me that the floor is broken into at least 4-5 separate sections. Not all the sections are at the same level - roughly 1-2mm height difference and the individual section flex when standing on an edge. I am far from an expert, but the concrete seems very soft and powdery.

We have contacted the housebuilder and they will send a surveyor around. I have no idea how much of a problem this is and would really appricate any comments/advice anybody here would have on this.

Many Thanks

Graham

 

[TexMex]

How bizare.
sounds like the site wasn't prepared properly. Usually, if the screed were to crack, it would still sit flat (ie have no rocking movement). Would be interested to find out the verdict, so please post a follow up after the surveyor has called.

Sorrry, I can't offer any help here. Just don't watch the film "Tremors" until this is resolved.

 

[2scoops0406]

If the screed is dry and powdery, it sounds like the wrong mixture has been used, why it should crack up quite so badly is a bit of a mystery, still if the house is < 10 years old this kind of problem should be covered under the NHCB guarantee.

 

[TexMex]

it sounds like the wrong mixture has been used

Still wouldn't account for the rocking though eh? Very weird.

 

[2scoops0406]

No, doesn't explain the large cracks, very strange.

 

[murraysnudge]

I think failure of the slab makes up the highest number of claims on NHBC. The slab can subside or heave. The beam and block floor is now very popular because it eliminates the problem of site preparation that Tex has mentioned.
The screed would normally only be 50mm but this sounds like the slab is cracked through to the DPM.
Unfortunately the NHBC don't have a really good reputation for settling claims, but I doubt if they can wriggle out of this one.

 

[masona]

Is there any movement on the outside walls ?

 

[grahamw]

The surveyor is comming tomorrow night. He has been sent by the housebuild so I will be interetsed to see what he says. We are thinking about getting our own surey done as well.

There's no cracks on the outside wall

I'll update with the surveyors comments on Monday. thanks for all the comments so far

Graham

 

[andemz]

Just out of interest do you have any underfloor buried heating cables like KIMA cable. that is only an interesting thought though. Quite probably movement, which will need to be monitored. What area do you live in and is it suspect to anyform of movement, have your neighbours had any problems?

You say recently built, what was the land sued for previously?

 

[grahamw]

Update...

The surveyor came and was not happy at all with the cracks. Next step will be to take core samples from various parts of the flooring and look at the concrete composition, reasons for the cracking etc.... This should be done in the next couple of weeks.

He wouldn't confirm or share his thought ab but by reading between the lines and noting to what he DIDNT say, the house could need complete new floor.

To answer andemz questions...

We have no underfloor heating and no cables/pipes are near the cracks. The area that house is built is clay, v.poor drainage. We did find out from a neighbour that another house in the street had a similar problem. Prior to building the land was unused, just wasteland.

I'll update when more news comes in

cheers

 

[masona]

Prior to building the land was unused, just wasteland.

Are you saying yours was built on wasteland, eg rubbish tip ?

 

[grahamw]

No, not rubish tip. I think the land for the development used to be part of a farm. I can sort of remember knocking around them when much, much younger.

 

[masona]

Okay, I remember watching a TV program sometime back regarding properties being built on ex-rubbish tip and ex-mine field causing gas build-up which gave movement to property.

 

[grahamw]

OK had the surveying done last week, they dug 4 large holes in 2 rooms around the house - still trying to get rid of the dust!

It turns out that the concrete was much thinner (less than 100mm) in the center of the rooms than at the edges. So it looks like they need to relay the entire ground floor. Not happy at all about this and not sure how it passed inspection.

BTW: they have said that it will take 3weeks to dig out and relay the concrete and let it dry. This seems very short to me, is this time frame realistic??

thanks

 

[IanDB]

And you thought the mess they made taking the samples was bad! Now you've got to have a new concrete floor - mega mess!!

Concrete normally takes about two weeks to dry reasonably (six months to cure completely but it's "only" a domestic floor so that won't affect you) so I would have thought the time frame seems just about OK.