What to do about 2 year old house with cracked concrete slab?

Question

While replacing our carpet we found (3) 10 foot long cracks in our concrete slab foundation. The house is 2 years old and the builder says this is normal. Cracks are 1/8 inch but one is about 1/4 inch wide.

Answer 1

Cracks in concrete are normal. As concrete hardens and settles after it is poured, the weight it puts on the ground can cause it to shift thus causing cracks. I poured a 1000yard slab last year 300ft by 50ft around 2ft thick and the only cracks it had were so thin paper could not be put in them. 1/4in wide is a cause for concern. A reputable contractor should work with you to solve the problem.

Answer 2

this isn't normal, either the mix contained too much cement or dried too quicky and shrank. The mix should ideally have contained a plasticiser to slow the drying process, or the slab should have been sprayed with water when part-dried.

If the concrete is also damp it would indicate that the layer of visqueen (plastic damp-proofing) is missing and the water in the concrete has gone downwards, speeding up the drying process. If the plastic was in place it would have retained all of the moisture, drying out slower

As concrete hardens to a peak over a 40 year period this will get worse

I would get a structural engineer to look at the damage before passing the report on to the builder. is the house still under warranty? if not you can still claim for shoddy workmanship.

The concrete floor is not load-bearing and could be dug up and replaced without affecting any other part of the building

Answer 3

Patching the cracks is in fact a good idea, and hydraulic cement is the way to go -- it expands slightly as it dries so it helps to fill cracks, but it will also leave a raised "bead" along the crack which you will need to take care of or you will have an uneven floor surface.


But you need to take a good look at the bigger picture. Why did the slab crack? Your builder is full of crap.
If cracked slabs are normal to him, he needs to find a better concrete contractor and you need to call him on the carpet for this. You didn't pay him to build you a house on a cracked slab. You paid him for a whole slab. The guys who poured the concrete should have known they needed to put expansion joints in the slab, or to pour the slab in segments seperated by an expansion barrier.

Sorry...
...getting wordy.

Keep an eye on the walls and cieling above and around the cracks. Especially above doors and windows as it is likely cracks will develop there as well. If so, the builder needs to come in and shore up you foundation at his expense.

Document every communication you have with him regarding this problem.

Answer 4

No this is not normal on a slab that is only 2 yrs old. One of our buildings is now over 10 yrs old and still has no cracks. The other one started to get cracks in less than a year and we had to get a different co. to tear it all out and re-pour the floor. We have since had no cracks in the new floor and were successful in our suit against the first contractor. This is the short story version though, but, no - not normal at all.

Answer 5

I would use something like crackmon to keep track of the cracks. If they get any bigger or if the slab on either side of the crack moves up or down then you have a problem. Cracks are normal for slabs.

1/4" is a little big though. I would put the crack mon on that one.

http://www.builderswebsource.com/tools/crackmonitor/crackmon.htm

http://www.prginc.com/pricelist-masonry.htm#flat

Answer 6

This should not be happening! Get a lawyer and an inspection and contact the builder. There is probably a warranty that covers such things but don't trust the builders. They will want to put a "band-aid" on it tell you every thing is fixed. It sounds like they screwed up when building the foundation and fixing it will be very expensive aside from fixing the cosmetic cracks and whatever else the inspector finds. This is serious and you should treat it so.

Answer 7

ask him if it normal for him to pay for the cost , of the repair ?

OK cracks happen,, really depends on what the soil was like before they built . i would suggest hes at fault .
you need to take pictures, then get three quotes, to repair this crap, maybe contact your insurance co;
then ask for a building inspector ,to take a look at this ,or an engineer, or both .
but make sure he pays up or pours a new slab .

Answer 8

Its not normal. He did a $&*^ job on the slab. I have a garage slab that is 50+ years old and it doesn't have any cracks in it.

Answer 9

Go to your local hardware and get some concrete caulking or some hydraulic cement and fill the cracks.

Answer 10

the slab should have been cut to relieve pressure points.but the builder is right its normall.it should not get any bigger than it is