Control Joints - Engineer Said He Made a Mistake!

Shortly after purchasing our new construction home we noticed that our hardwood floors on our monolithic slab we separating. After walking the exterior of the home we discovered that along the same lines/areas that the hardwood flooring is separating there are cracks visible on the exterior of the foundation.

We have only been able to investigate under the carpeted areas in our home as majority is hardwoods and have located the cause of the hardwood flooring separating, control joints. We believe the 4 control joints (2 north to south and 2 east to west) are much to wide and deep (we have pictures during construction that show their placement). They are approx 1/2” wide and have large cracks in them that appear to have cracked all the way down to the vapor barrier (I’m also concerned about moisture as the hardwood flooring is splintering and separating underneath the top). This is a huge concern for us as almost every room on our lower level has a joint running through it.

The builder sent his engineer to look at the areas under the carpet (since the rest is under the hardwoods) and the engineer stated the joints should be 1/8” not 1/2” wide. He said that all the areas under the hardwoods would need to be stitched in addition some type of underlayment over the joints before reinstalling the hardwoods and the areas under the carpet would just need pressure epoxy and that we will continue to have problems unless it is addressed. He put this all in a report as well. The builder agreed to fix the issues. A few weeks later the builder and the engineer showed back up and the engineer stated he was mistaken and to disregard his state sealed report that the joints are not too large. Now the builder will not fix the control joints in the slab.

We are concerned as this seems like it would be very costly to fix in addition the 2000 square feet of hardwood flooring will have to be removed and replaced. We feel potentially the value has/will decreased as we would need to disclose this when we sell our home. This isn’t a job we can afford to fix ourselves. Any other opinions if indeed the joints are too large and if the engineer’s initial remedy is correct?


New construction you say? Time to get your attorney involved!

Control joints are designed to prevent random cracking generally in slabs. It appears to be a slab on grade construction. For the cracks to have extended through to the exterior perimeters of the footings to the degree you are showing is indeed very unusual. The separation is also of concern as it appears the steel reinforcement in the slab and footings is not adequate or wasn’t in place when the concrete was placed. There are firms that will “scan” the concrete and give you a better idea of what’s going on. The engineer can only comment on what he sees. Perhaps with a digital image of the steel he will see beyond his earlier statements and comment accordingly. I would hire an engineer (structural) for $500.00 to survey and consult with you and the contractor present and not rely on the contractors engineer at this point.

Like I said…

I agree with Rick, get your own engineer to look at it. I would and the first engineer for everything to be in writing. If it’s ok, ask him for the reason he changed in writing. Also, tell him you will be getting a second opinion.

Entire sections of concrete shouldn’t be moving even with 1/2" control joint. May be poor sub-compaction and related concrete movement. The extra wide control joints may have given it an easier way to move in that location. The cracks may not have been 1/2" originally, but have spread open.


That control joint may have been 1/2" wide at the top initially, but widened as the concrete dried. As others have said all concrete shrinks and cracks as it dries, but these control joints force the cracks to occur at these saw joints. Depending on the configuration of your slab the shrinkage may not occur uniformly, which is typical. You should see the crack on the outside of the foundation at each saw joint, which is expected. I don’t know how quickly the flooring was placed after the slab was poured, it could take several months before the slab dries out. Anyone placing tile or hardwood on a concrete slab must take shrinkage and moisture issues into account. This may not be a foundation issue, but a flooring issue placed too soon. To narrow down the cause an engineer will need to know, concrete mix design, subgrade compaction, soil type, reinforcing steel, environmental conditions on the day of the pour, when the flooring was placed, flooring manufacturer’s specifications, contraction joint layout pattern, etc.

Randy, Great info as usual, but please help the OP out here… In your opinion… WHO should be contacted to make this right as the builder obviously has washed his hands of any responsibility?


It depends on the answers to the items I listed. For example, if the concrete mix was good and was laid on well compacted material and the amount of shrinkage was normal based on the slab length then I would say the flooring guy may have a dog in this fight. If the contractor, flooring guy and the homeowner have no documentation, then everyone goes to court and everyone loses, except for the lawyers. This is a prime example why homeowners should have a well written contract with detailed specifications and should hire someone to do quality control. All commercial projects typically have contracts, specifications and someone to manage quality control.