Cracks in Foundation 1

[andro1]

Hello,
We are building a home in North Dallas and concrete was recently poured on for the post-tension slab (one week ago).
When I went to the site today, I noticed that there were several cracks all hairline. Once crack that concerns me is on what will eventually be the master bath. This crack runs all the way to the edge of the slab and then vertically into the ground. Thickness wise, its still hairline. I tried inserting a penny into the crack and it did not go in.


Framing has already started and the cables are not yet tensioned.

1)What is the maximum one can wait prior to tensioning the cable?

2)Should I be concerned enough to have a structural engineer separate from the builder inspect?

3) What is my course of action if the builder disputes the independent structural engineer's findings?

Appreciate your help.

Andy

 

[boo1]

Post tensioned slab on grade construction is common in the west coast and Texas. After the concrete has cured and obtained the necessary strength, the wedges are inserted inside the anchor casting and the strand is stressed,usually between 3000 and 3500 psi . The post tension institute (PTI) has a design manual for a post tensioned slab on grade.

http://www.post-tension.org/info_software.asp

Shrinkage is a main cause of cracking. As concrete hardens and dries it shrinks. This is due to the evaporation of excess mixing water. Is it a problem, probably not. The reinforcement will hold the slad together. Is the plan engineered? (contact them first)

If you are hireing an Engineer (definitely seperate from inspector) consider the following:
The first field activity is a thorough visual inspection. All visible defects are recorded, photographed, measured, and analyzed for potential destructive/invasive testing.
The way to establish physical properties of concrete in structures is to obtain samples and then test them in the laboratory. Using a diamond-tipped coring machine, we cut through the concrete slab and obtain standard size cylindrical specimens.

Courts will seperate the dispute if it goes that far.

 

[andro1]

Thanks for your reply. I will check with the builder if the plan was engineered. I did see a diagram that showed the layout of the cables and a certificate from the foundation design firm certifying compliance with the Post Tension Institute plan.
Given that this is not a custom home, I wonder if they engineer individual homes or just the model.

Andy

 

[Focht3]

Proceed with caution. Portions of the Metroplex are underlain by the Eagle Ford Shale - a highly expansive formation. The cracks could be an indication of future problems. Do your homework now. Get a god geotechnical consultant now - spending $1,000 on him/her could be the thing that helps you sleep at night when this is all over. And start shopping for a good lawyer that specializes in construction defects. You may need him/her soon.

Do not rely on the courts to sort this out after you have taken possession - you can get hosed. Your contract probably has an arbitration clause in it - a bad deal for consumers. Get out now if you aren't comfortable about the foundation.

And start a very detailed notebook now - spiral bound, not loose leaf. Record the results of every meeting and conversation as it occurs. And take lots of pictures. Spending $200 now on documentation could save you $10,000 or more in headaches later.

I'm currently serving as an expert witness on a similar case in San Antonio...and I wouldn't want to be the homeowner.

 

[andro1]

Thanks for the cautionary words. I am taking as many pictures as I can, visiting the site almost every day.

I guess the essential problem is the distinction between non-critical hairline cracks and groundshift.

Would any of you know the ramifications of "walking"? i.e. I have already signed the contract and paid the advance and 1/2 the upgrade fees. If at the point of closing, I am not happy and decide I don't want to, can the builder sue?

Obviously, this is a last case resort. We do want the house but don't want to be stuck with a lemon.

Andy

 

[Focht3]

You need an attorney to answer that question - that's outside the engineering realm. Get an attorney quickly -

You need to be assertive now - passive behavior will get you nowhere. Try to switch to a different lot - with little or no cost to you. If that works, hire a testing lab to sample and test the concrete for the new slab. It will cost less than $200 - cheap insurance. Also hire a structural engineer to observe the PT cables before the pour; if he says they're wrong, notify the builder. If they don't fix it before the pour, you have (engineering) grounds to terminate the contract.

For what it's worth, I had to fire my first builder - and I'm "in the business." So I have personal experience with this issue; my suggestions aren't strictly from a professional standpoint.

 

[boo1]

See the Texas Section of the American Society of Civil Engineers foundation guides:

http://www.texasce.org/DocumentReview1.cfm

 

[Focht3]

Be careful of those documents; they were developed by an "invitation only" - type group. Sorry mess, those documents. (Don't let anyone "buffalo" you with those -) I have lots of criticisms of them; it originaly started with documents being prepared by largely the same group under the "direction" of the State Board. (Now THAT'S a story!)

The documents show "muddy" thinking; for example, there are three types of "foundation" consultations: 1) owner says, "Help me fix my property.", 2) insurance company asks, "Is this foundation damage a covered loss?", and 3) a construction claim where the questions are, "Is it a defect? If so, who is responsible?" Each has a slightly different starting point, with differing levels of investigation required - and different levels of care. Yet those documents lump all three together.

It could have been a good document - if the group had strong leadership and an able editor. But egos and politics...

 

[boo1]

Focht3 thanks for the document review. I only posted them for a reference link.

 

[Focht3]

I had guessed that you had not studied them as well as I have. I was doing a lot of forensic work during that time frame - issues were fresh for me.

The documents do have some utility; but they aren't "Gospel."





Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[boo1]

I dont have the exerience too to be able to comment on the articles content.

 

[mesampah]

andro1...We are also building a house in the N. Dallas area and we have the exact same issue. What did you end up doing? Did you hire an independent inspector? Did you buy the house? Do you have any advise?

 

[andro1]

mesampah,
Actually, I did end up buying the house. Considering that I was already about 8K out of pocket (advance+upgrades), there was not much I could do.
However, I did get the foundation inspected by a structural engineer. It so happened, that the engineer did the inspection the same day the cables were being tensioned, and he could verify this too. He did'nt seem concerned about the cracks and neither did two inspectors who did the home inspection over different times. I also cold-called a foundation company (forget its name) and just happened to get to an engineer and talked to him. This re-assured me too.
I have moved into the house for about a couple of months now and so far so good (fingers crossed). Most of the cracks disappeared after the cables were tensioned (these have also been covered up by the carpet/tile/wood etc. There are a couple of cracks in the garage floor I wince at every time I see though.

The bottom line however is (this is purely from my perspective as a layman and should not be construed as professional advise):
1) Apparently drying cracks are possible. However if there is heaving i.e. one side of the crack is higher/lower than the other thaen there is ground movement and you should take more care.
2)I am going partly on faith. I discovered these cracks since I was at the site almost every day. If I were buying a spec house with carpets already laid, there is now way for me to know what I am getting into
3)I'm trying to take a more measured approach to foundation problems. Sometimes the problems associated with moving foundations can be overwhelming but problems can happen anytime. You could have a house with no foundation cracks, move in, get some really dry weather and associated watering restrictions and find foundation problems.

So for better or for worse, this home is mine now! Best of luck to you and please take as much precautions as possible and try and get professional advise if you are worried.