Cracks in new house foundation, normal?

[johaninroseville]

We are in the process of buying a new house from a major homebuilder in Northern California.

We are at the house almost every day to check the progress and to inspect, in any way we can.

This week we found big cracks in the floor of the house, in almost every room.

I can see that they filled the cracks but my concern is that once the floor is in, and if more cracks appear, than what will happen.

The concrete slab was poured at least two months prior to the cracks appeared.

We checked the other houses on the street. Same builder, same models, and none of the other houses had any cracks.

Steel reinforcement bar was installed in the slab in a mesh fashion.

What should I do?

Should I contract an expert to check it out, or is this considered to be normal, and I am just a little paranoid?


I would appreciate any help with my worries.
Pictures may be viewed at See the pictures of the cracks (http://www.thelarssons.com/cracks/)

My email is johan@thelarssons.com

[mjpliv]

Please tell me they didn't pour concrete over grass!!!!!!!!!!!!!!!!!

[johaninroseville]

I beleive they put gravel on top of the grass, and then the steel bars.

[mjpliv]

I don't know how they do things in California but I have never seen any concrete structure, load bearing or otherwise, successfully placed on any type of organics. Rich, is this an acceptable practice anywhere in the U.S.?

Say it ain't so, Joe! Say it ain't so!

[Rich]

It's never acceptable to pour any structural concrete over any organic material. Eventually it decomposes/deteriorates and you end up with voids below your slab.. i.e. cracking.

[johaninroseville]

Is it up to code? California Code?

[Rich]

I don't think California or many other states have to inspect rebar in slabs.. only footings and stemwalls. Essentially is what I'm saying - I personally don't think it's up to code but since the inspector probably didn't see it - who's to say what's under there. If the inspector did see it then he should be fired and never allowed in another building :)
If you really want to push the subject you could take your pictures to an inspector but I don't know if I would open that can of worms.

[johaninroseville]

I hear you. But the potential future problems of building on organics might be a bigger can of worms, correct? I sent the pictures to the county's chief building inspector. He was sending out an inspector to check it out - wiating to hear back from them.

[johaninroseville]

The builder left me message:
"Everything is OK, the cracks are normal in the curing proccess. We have patched the cracks, and they are nothing to worry about - case closed"

Still waiting to hear back from the County inspector.

My concern is any new cracks that might appear once the flooring is installed, and will not be filled. I realize that hairline fine cracks are normal when concrete cures, but these cracks are 1/2 inch wide.

Am I just being paranoid, or are my concerns valid?
After all, I am not a costruction worker.

[Rich]

I've poured thousands upon thousands of yards of concrete and a good portion of that is slabs.. if something we poured had anything more than a pencil lead crack we would rip it out and we'd consider ripping it out if it was under that size.
If it's on organic material you'll have worse cracks than that before you're done.

[johaninroseville]

Is there any way to repair cracks like that, or does the foundation need to be reconstructed?

[RobBase]

First, as a new guy here, let me say hello. Also hope not to stir up too much stuff with my post.

Next to Johan and your cracks......

1. In general, if your builder was smart he would have stripped off all the topsoil before starting your foundation. He might have stripped it off long ago in which case grass or weeds could have begun to grow back in the subsoil. It happens sometimes. Hopefully that is what he did although the soil in the pics looks somewhat dark like topsoil. Soft, loamy topsoil under the slab I would worry about, grass I wouldn't.

2. Also, I didn't see picstures of the slab prep work, but it looks like he put in at least 6-12" of gravel under your slab (up to the top of the turned down edge previously poured) which is usually enough to offset the bad effects of some topsoil or grass underneath of it.

3. Your cracks seem to be caused by a wet mix poured on a hot, dry day possibly without a polyethlyene barrier underneath the concrete. Maybe he didn't spray curing compound on the slab right after finishing also or cure it properly by other means. Whatever caused it, they look like shrinkage cracks, not structural cracks. Hopefully he put the wire mesh in it like you said and pulled it up as he poured.

4. The reason the cracks are so wide is it looks like the builder had his crew go in there and open them up with a V-groover on a small grinder so that he could patch them up better. What he patched them up with I can't tell although it looks like tubes of caulk laying around. Caulk is a decent material to patch the cracks with although some epoxy grout would have been better.

5. In any of the rooms where there will be carpeting or sheet goods, you should have nothing to worry about regarding the cracks. You will never know they are there unless they open up during an earthquake. :wink:

6. As far as the cracks in the bathrom/kitchen where there will likely be tile, that's a different story. The patches they did should be okay but to be sure, and I don't know the legal mumbo jumbo regarding what I'm about to say, but perhaps you could have some kind of document or warranty written up and signed by the builder guaranteeing the soundness and "crackfreeness" of the tile installations he will be putting in. Hopefuly you'll have a home warranty from him that will say this already.

7. The reason the other houses in the area didn't have cracks could be anything including; diffent weather conditions during the pour, different concrete mixes, different concrete crews that didn't add much water to the concrete once it arrived, etc.

8. Since California doesn't really have a freeze/thaw cycle like we do here, your cracks should remain stable and trouble free as long as you live there. Now if you do happen to have freeze/thaw in your area, they could open up and cause problems. I personally would not want a house with cracks in the slab, but I've seen enough slabs that had them and nothing ever became the worse off because of them.

Good luck.

[johaninroseville]

Hi,

Thanks for the long reply. I appreciate it.
The county has done a reinspection of the house, and if they also state that everything is ok I will settle with a written liability from the builder.


Have a great weekend, and thanks again.

Johan

[mjpliv]

Rich, I just went back and looked at those pictures again. It looks like they only used a concrete form on one side. The other side looks like they just dumped concrete untill it was high enough to put a flat spot on top for the wall plates.

Are my eyeballs screwed in crooked or is this the normal way to do things in California?

[johaninroseville]

I talked with the countyinspector today and he ensured me that everything was up to code. Should something happen in the future I have all of the photos etc.

Thanks a lot for the help guys.

It’s admirable when people like you take time to help others – Thanks again.


Johan

[Rich]

Huh.. I didn't notice it before either. I've trench formed footings before but never one sided a footing. I wonder what slump they were using and how many voids there are because of it.
Rich, I just went back and looked at those pictures again. It looks like they only used a concrete form on one side. The other side looks like they just dumped concrete untill it was high enough to put a flat spot on top for the wall plates.

Are my eyeballs screwed in crooked or is this the normal way to do things in California?