This was the slab the day of the pour:

http://i.imgur.com/QCem2Pm.jpg

The crack started about a week later. It starts near the front of the house where the garage is and spans the height of the slab:

http://i.imgur.com/I8ovO3q.jpg

We are looking across the garage to the main part of the house and you can follow the crack up and to the left:

http://i.imgur.com/u40t3jk.jpg

It gets to the middle of the house and then T-bones and the new perpendicular crack spreads the length of the house:

http://i.imgur.com/x4s40og.jpg

For some idea on the width:


http://i.imgur.com/b5nB9hx.jpg



http://i.imgur.com/BtmnED7.jpg




The builder didn't notify me of the crack, my realtor did. I wrote them an email the following morning discussing my concern and this was their response:

quote:

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We are aware of the settlement, please also know that your slab is a post tension which means the cables that are in your foundation are stressed 10-30 days after the pour. The cables are should be stressed later this week at that time our engineer will be out to do a stress test, and visual inspection. Also know that our engineer was on site with myself durning the pour to test the concrete to meet set standards. As of right now there is no know problem seeing we have not stressed the slab, I will let you know as soon as I hear from our engineer. Also we are looking to start framing Monday of next week.

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I've gotten mixed responses from people around me. Some are alarmed, some that are in the field say not to worry. I can't help but be concerned, the crack spans the height of the slab and (nearly) the width and length of the house. And we only poured 8 days ago. Just imagine when we start putting some weight on that concrete with our cars and the house itself. Am I panicking or is there real concern? I appreciate any help.

I'd call a foundation company and ask their opinion. Pay for it for peace of mind.

Absolutely. Unfortunate but worth the added insurance via expert opinion.

People behind us had a crack in slab, builder saw it and had engineer come out. The engineer said it was ok and not major. Builder still tore up concrete and started over because they thought it was the best thing to do.

Thread on here a couple of weeks ago

As noted on that thread, concrete is gonna crack. It's what it does. If you want a neutral opinion, I'd find an engineer to look at it, but someone with experience in PT slabs, and someone who isn't going to dismiss the concept from the get do. Foundation companies have skin in the game.



[url=http://texags.com/forums/61/topics/2666293/replies/44259573][/url]

i am not sure what your contract/agreement is with this builder and if you own the lot or not but seeing that type of crack would make me seriously consider walking away from it.

I have always been told you expect to see surface cracks but there should be concern when the crack goes vertical at the edge. Not sure if this is still the case on a post tension slab.

I have the same opinion as others in the other thread mentioned that post tension should help long term but this cracks of this nature this quick would make me think something was not done properly.

I have no expertise in concrete slabs but I can say that I am in the beginning stages of building a house and Over the last 6 months I have walked through at least 50 homes and never seen a crack of that size.

Get your own engineer.

They are right in that the post tension cables should not be tensioned yet. IIRC the concrete has to hit 40% strength first.

Surface cracking is simply going to happen, but this one looks serious to me because it goes vertically through what looks like a grade beam. Just because their cylinders may have come out ok doesn't mean that something wasn't installed incorrectly. The compressive strength of concrete is only half of what gives the slab its strength. You also need steel reinforcement and the tension of the cables for tensile strength. If they failed to install their steel reinforcement correctly, that could have caused the slab to prematurely crack and lose strength. However, it may be ok if once they stress the cables the slab pulls together and functions monolithically instead of as two big pieces.

If the slab is fubar, your contractor has a very big interest in not redoing it. They stand to lose quite a bit unless they have E&O insurance that will cover an incorrect installation. Again, I would get your own engineer that your contractor does not have a relationship with, just to confirm the integrity of the slab.

We have a home built in 1976...we moved in Aug 1 1978. We have no idea what the slab originally looked like but 78-80 were very very dry years so somewhere it shifted. In May 82 we found out it had shifted enough to pop a hot water line in the slab.....we have had multiple issues with the house shifting since then. Your crack seems big and I would get an engineer to check it ASAP and again after the slab cures completely...absolutely no more building until it is checked out and I was satisfied. Stupid builder, it's in his best interest to wait as well...if the slab is compromised.

Some hairline fractures are normal on a slab and will be gone when it is tensioned. Then new ones will form. It's the nature of thee beast. However; with the cracks going through the exterior beam and being that wide I would be cautious.

Ask your super and sales person to stop progress. Remember to get your sales person involved as they have the most incentive to advocate for you within the company, you control their paycheck.

Be involved; if you have time meet their engineer on site and look into bringing your own. Tell the builder that they should not proceed until it is cleared by the designing engineer and only AFTER you personally receive a letter from their engineering company that states the slab is not broken and that they will fully warranty it for ten years.

Keep up your cautious attitude. You're doing the right thing by cataloging all of this.

Slabs shouldn't crack that bad that fast. Don't accept whatever happy talk BS the builder is giving you. They are are right up there with used car salesmen in that category. Get your own outside expertise.

Cracks big enough to stick quarters in would have me concerned too.

To any of the residential guys here - on a slab that size why are there no control joints cut? Is that not typical practice in the home building world?

OP - is that the only crack in the slab?

Also, do you have access to the plans and specs for your home? You might want to check there and see if this goes against any specs. You may also want to ask for the mix tickets on the concrete and verify that the mix received was the same as the mix specified. I don't know about residential, but in commercial we keep detailed logs and mix tickets for every pour we do.

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To any of the residential guys here - on a slab that size why are there no control joints cut? Is that not typical practice in the home building world?

OP - is that the only crack in the slab?

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One of the selling points of post-tensioned slabs is the elimination or reduction of control joints. OP's design engineers may have tried to design them out, or it may simply be a small enough slab on good enough soil that it doesn't need them.

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Also, do you have access to the plans and specs for your home? You might want to check there and see if this goes against any specs. You may also want to ask for the mix tickets on the concrete and verify that the mix received was the same as the mix specified. I don't know about residential, but in commercial we keep detailed logs and mix tickets for every pour we do.

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At best, there's a single 8-1/2"x11" sealed foundation plan with chingo notes on it someplace. Residential, especially with production builders, is a whole 'nother world from commercial.

But you never know. There could be detailed info sitting in a job trailer someplace, underneath pages 2-16 of the playbook that Spav tossed. But I digress...

quote:

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To any of the residential guys here - on a slab that size why are there no control joints cut? Is that not typical practice in the home building world?

OP - is that the only crack in the slab?

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Post tension shouldn't require any expansion joints and you typically won't want any expansions on your slab. I've never put one in any slab I've done, including the 7 to 10 thousand sq ft slabs. Just deeper, wider, more frequent beams.

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Also, do you have access to the plans and specs for your home? You might want to check there and see if this goes against any specs. You may also want to ask for the mix tickets on the concrete and verify that the mix received was the same as the mix specified. I don't know about residential, but in commercial we keep detailed logs and mix tickets for every pour we do.

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At best, there's a single 8-1/2"x11" sealed foundation plan with chingo notes on it someplace. Residential, especially with production builders, is a whole 'nother world from commercial.

But you never know. There could be detailed info sitting in a job trailer someplace, underneath pages 2-16 of the playbook that Spav tossed. But I digress...

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A whole lotta this!

Production guys tend to keep their pour tickets for about the amount of time it takes to get to the job trailer and trash them. The plans also won't do much good either as everything you need to see is already covered. I always take a bunch pictures of the pre poured slab just in case something needs to be looked at after concrete is placed.

Depending on what city you are located in, the permitting authority may have a copy of the drawings on file. At the least, you should be able to obtain them under an open records request.

I can't weigh in on the engineering parts of this, but will just add some common sense, or at least what I think is common sense:

1) that many cracks, at that size so close to when it was poured seems really odd
2) Let's say you do frame the house and live in it with your cars and such...I would think as the foundation continues to shift/move/crack, it would show on the interior too. The builder is going to have a headache either way with all your warranty claims.

Fix it now before you move in and then get into a really big bind.

Worth every penny to get an egineer and if you can make the builder pay for it I certainly would.

2

I asked a structural engineer and here was their response after reading the post:

quote:

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A crack like this is common when the curing process allows the slab to set (cure) too fast. However, the key fact here is that I read that it is to be post-tensioned? Until the cables are stressed there is no reinforcing working in the slab. All the cables are in plastic sheaths so they can be pulled. I have found that these slabs will develop a crack like this approximately 50ft. in from the short edge. When you stress the cables the crack closes up.

I would not panic until the cables are stressed. If they are done properly and pulled to the proper elongation and stress the crack should close up.

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HTH

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Also, do you have access to the plans and specs for your home? You might want to check there and see if this goes against any specs. You may also want to ask for the mix tickets on the concrete and verify that the mix received was the same as the mix specified. I don't know about residential, but in commercial we keep detailed logs and mix tickets for every pour we do.

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At best, there's a single 8-1/2"x11" sealed foundation plan with chingo notes on it someplace. Residential, especially with production builders, is a whole 'nother world from commercial.

But you never know. There could be detailed info sitting in a job trailer someplace, underneath pages 2-16 of the playbook that Spav tossed. But I digress...

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I know that's how it works, but what do they submit to the city? Something has to specify compressive strength and composition, right?

quote:

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I asked a structural engineer and here was their response after reading the post:

quote:

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A crack like this is common when the curing process allows the slab to set (cure) too fast. However, the key fact here is that I read that it is to be post-tensioned? Until the cables are stressed there is no reinforcing working in the slab. All the cables are in plastic sheaths so they can be pulled. I have found that these slabs will develop a crack like this approximately 50ft. in from the short edge. When you stress the cables the crack closes up.

I would not panic until the cables are stressed. If they are done properly and pulled to the proper elongation and stress the crack should close up.

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HTH

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All of the post tensioned slabs I have ever seen have rebar in them as well as the sheathed post tension cables, but this is also residential and not commercial. It's also sitting on the ground, so there is a lot less need for immediate tensile strength since it's not above a crawl space.

I do also think the crack will close up and the slab will act monolithically, but I'm not an engineer. If this we're any of our slabs, we'd have a serious problem, but the OP's is a slab on grade, not a suspended slab. If anything, the OP might want to be out there for the tensioning.

quote:

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I asked a structural engineer and here was their response after reading the post:

quote:

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A crack like this is common when the curing process allows the slab to set (cure) too fast. However, the key fact here is that I read that it is to be post-tensioned? Until the cables are stressed there is no reinforcing working in the slab. All the cables are in plastic sheaths so they can be pulled. I have found that these slabs will develop a crack like this approximately 50ft. in from the short edge. When you stress the cables the crack closes up.

I would not panic until the cables are stressed. If they are done properly and pulled to the proper elongation and stress the crack should close up.

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HTH

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This was the consensus on the other thread along with pictures of slab cracks closing up within hours of the cable tensioning.

quote:

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quote:

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I asked a structural engineer and here was their response after reading the post:

quote:

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A crack like this is common when the curing process allows the slab to set (cure) too fast. However, the key fact here is that I read that it is to be post-tensioned? Until the cables are stressed there is no reinforcing working in the slab. All the cables are in plastic sheaths so they can be pulled. I have found that these slabs will develop a crack like this approximately 50ft. in from the short edge. When you stress the cables the crack closes up.

I would not panic until the cables are stressed. If they are done properly and pulled to the proper elongation and stress the crack should close up.

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HTH

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This was the consensus on the other thread along with pictures of slab cracks closing up within hours of the cable tensioning.

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I started the other thread and found this to be true. Of course the cables have been stressed at this point and the crack is visible, however barely! I see nothing to worry about, as our home was poured with all rebar (not post tension) and we had this type of very hairline cracking in our slab. I think so long as the cables are stressed correctly, you have nothing worry about.

However, longevity, is something that my folks certainly are worried about, as you are. It all seems fine now, but never really know about the future. Check your builder's warranty and see what it looks like, if you haven't already.

quote:

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Also, do you have access to the plans and specs for your home? You might want to check there and see if this goes against any specs. You may also want to ask for the mix tickets on the concrete and verify that the mix received was the same as the mix specified. I don't know about residential, but in commercial we keep detailed logs and mix tickets for every pour we do.

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At best, there's a single 8-1/2"x11" sealed foundation plan with chingo notes on it someplace. Residential, especially with production builders, is a whole 'nother world from commercial.

But you never know. There could be detailed info sitting in a job trailer someplace, underneath pages 2-16 of the playbook that Spav tossed. But I digress...

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I know that's how it works, but what do they submit to the city? Something has to specify compressive strength and composition, right?

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Therein lies the "chingo notes" on it. It's a house, not a new two-story middle school. A handful of notes on the 8-1/2x11 will cover it. It doesn't have the size, reactions, details, leave-outs, etc. that a commercial project might have. Could it be more detailed? Sure, but you aren't going to get that from KB, DR Horton, etc. And there is a point of diminishing returns in full on plans for a house.

From CoSA's DSD site, for example,

quote:

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Foundation plan of sufficient detail to show conformance to the provisions of
the IRC including but not limited to: 1) size, spacing and strength of reinforcing
steel 2) foundation requirements of braced wall panels if required in braced wall
plan. The foundation design must be by a Texas Licensed Architect or
Engineer, or submit a geotechnical report with a foundation design (Note: all
post tension foundation designs must be prepared by a Texas registered
professional engineer).

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Now compare the above to what's required to get Structural approval for a permit on a commercial project.

I'm not a very good foundation engineer ( I deal with pavements primarily), however I work for one of the largest concrete producers. This looks to me like a few potential issues: 1. Early age concrete cracks occur due to loss of water during the curing process. Often, the contractor will add water to the mix to mare it easier to move around and finish, however additional water beyond the mix design will increase potential for additional shrinkage. Additional water could also be the fault of the producer, especially the lower end producers, lower quality. This looks to me like the mix was probably too wet during placement. If that is the case, the compressive strength cylinders should break low at 7 and 28 days. Low compressive strength doesn't cause the crack, but higher than needed water content does and it can cause low compressive strength.

2. Another possibility is poor or inconsistent support under the slab. This could happen due to poor compaction, or some inconsistency like bad compaction around a pipe or something. If you have pictures before the slab was poured, I'd document those just in case.

Given the location of the crack, the shape it takes across the slab, and the width, I'd personally be nervous about it. While the post tension will likely tighten it, it seems decently wide to me, and I don't like the shape. I would document it myself, get the contractor and salesman out there and document what was said. I'd then document the post tensioning results. If they have any concerns about it and know your serious, I'd bet they will make the right decision because as they proceed from here, the cost of repair begins to skyrocket.

This seems to be the thread to ask: What is the recommendation regarding watering a foundation?

The reason to water a foundation is to keep the water content in the soil consistent, especially if your slab is on clay soils. When the water content changes in clay, it will either shrink or swell and cause your slab to move as well as walls and doors. So, the answer depends on where you live, how much rain you've received, and if you have a sprinkler system. The name of the game is consistency.

Appears to me there is likely some fill on the low side of the crack - which was not tamped to proper density to match undisturbed earth... ...or some such...
And, there are apparently no interior grade beams or the crack would not be running across the foundation instead of along a line.
Just guessing but looks like Slab likely grade beam exterior only with matte rebar interior. May or may not have drilled footings? Finish looks good, but not on "solid ground"... The old "build your house on solid ground and not sand" applies... (loosely applied from parable...)...
Soil in much of Texas from Bryan to Dallas is heavy clay and will "move" depending on water content of the soil... i.e., if the soil was dry when the foundation was placed, and there was significant rainfall soon after - and it collected on/near/under(?) the foundation, the soil under the slab could literally swell up and form a dome (however slight) - and thus crack the foundation. It is not unheard of that a spring starts up during wet weather but during dry as the last few years and unknown until it rains a lot...
Minimal (one or two maybe) "Hairline cracks" are usually OK.... (no coins in cracks however!!)...
This one is already beyond that - and depending on loads, soil density, water absorption, etc., could all be a factor in future continuing of the crack...
For instance, if a brick facade is indicated, and the crack extends to the exterior wall, the brick will likely also crack along mortar lines... and possibly have floor separation where ceramic tiles or wood flooring is installed.
You have a problem that needs to be addressed before further work is done.
I'd be surprised if the authority having jurisdiction over permits would allow the contractor to continue - especially if it is brought to the contractors attention.
Hard to correct after the pour - but easier now than later with structure on it...
As noted above - if the contractor or permitting agency gives you grief, get an engineer and if the engineer agrees, proceed with his recommendations.

OP,
You've asked the builder the question and will likely get one of two responses

1. It's effed and we're gonna fix it or start over
2. It's fine, or will be once tensioned, and we're gonna continue

If you have concerns with how they potentially plan on fixing it, or it happening again, or the fact that they continue, let us know whereabouts you are and one of us can probably help you find a structural engineer to look at it. A couple hundred bucks buys a whole lot of piece of mind, especially compared to the cost of the home. If there is a problem, you can probably pass the cost back to the builder.

Most everyone on here (myself included) doesn't know the type of soil, the design of the slab, the conditions of the pour, what the rest of the slab looks like, who poured it, etc. It seems the longer the thread goes on, the more spitballin' (albeit educated spitballin') you're gonna see based on a lot of F ups folks have seen over the years, until we all collectively scare you outta living in any house.

I think everyone would agree it warrants at the very least a second opinion. I would also think everyone agrees that ought to be a neutral second opinion. Beyond that, we're gonna go back to arguing about PT versus traditional slabs on grade, using chairs versus blocks, and Kyle versus Kyler.

quote:

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OP,
You've asked the builder the question and will likely get one of two responses

1. It's effed and we're gonna fix it or start over
2. It's fine, or will be once tensioned, and we're gonna continue

If you have concerns with how they potentially plan on fixing it, or it happening again, or the fact that they continue, let us know whereabouts you are and one of us can probably help you find a structural engineer to look at it. A couple hundred bucks buys a whole lot of piece of mind, especially compared to the cost of the home. If there is a problem, you can probably pass the cost back to the builder.

Most everyone on here (myself included) doesn't know the type of soil, the design of the slab, the conditions of the pour, what the rest of the slab looks like, who poured it, etc. It seems the longer the thread goes on, the more spitballin' (albeit educated spitballin') you're gonna see based on a lot of F ups folks have seen over the years, until we all collectively scare you outta living in any house.

I think everyone would agree it warrants at the very least a second opinion. I would also think everyone agrees that ought to be a neutral second opinion. Beyond that, we're gonna go back to arguing about PT versus traditional slabs on grade, using chairs versus blocks, and Kyle versus Kyler.

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X1000

Get an engineer to give you a sound answer that is not biased in any way! Small amout of money well spent consideering the major investment your making!!!

Like many of said, hire your own engineer. That does not look very good.
We have done a fair amount of expert witness stuff for structural concrete as it relates to pools and we always start by sticking a quarter in the crack. If it fits.......
The potential problem will only get more difficult to address.
Good luck with this!

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The Post-Tensioning Institute recommends that the tendons be stressed between 3 to 10 days after the concrete has been placed and has obtained a minimum compressive strength of 2000 psi. The time between placing and stressing is an issue because the tendons are "unbonded" to the concrete and are effectively useless for crack control as the slab cures and shrinks. Until the tendons are stressed, the slab is essentially un-reinforced, and, if left in this condition, noticeable cracking is to be expected. I have unfortunately witnessed numerous slabs that have experienced substantial cracking simply because the contractor waited 3 to 4 weeks to stress the tendons. A standard fix is to rout out the cracks and inject epoxy, but the fix is not aesthetically pleasing and has left many a homeowner unhappy.

There is no difference in the concrete used between post-tensioned and conventional foundations. I recommend a minimum compressive strength of 3000 psi to allow the mix to reach 2000 psi within a few days and the tendons to be stressed within a week of pouring the slab. Since a post-tensioned foundation design is based upon allowable stresses, higher strength concrete (up to 5000 psi) has been used instead of increasing the slab or beam depths. In most cases, the compressive strength is based upon the sulfate content of the soil. Per ACI table 4.3.1, moderate and above levels of sulfate require between 4000 to 4500 psi concrete with a maximum water cement ratio of 0.45.

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SOURCE: http://www.concreteconstruction.net/concrete-construction/post-tensioned-slab-on-ground-foundations_2.aspx

• Engage a registered professional (structural) engineer not associated with the builder
• Request mix designs and batch tests from the builder (any engineer you talk to will appreciate this info if its available)
• Ask when stressing of the tendons is scheduled (if you don't already know this)
• Take a floor plan of your home and draw where the crack is - once everything is completed it is possible floor finishes such as tile could be affected

I had a new house that we found a crack like this in because tile had cracked. Had a structural engineer look at it. It was within spec and the slab was performing fine.

Problem we had, the tile couldn't handle the movement in the slab. You have to have a more forgiving floor that can handle the movement.

Any builder that puts tile on a post tension without an underlay is asking for problems. Fortunately, they are just cosmetic.

I would be more concerned about the long term repercussions of something like that than the short term. I.E. when you go to sell it 10 years from now, how many buyers are going to be turned off by that crack?