This is a follow-on to the Bamboo floor cupping problem and is a timely topic for me.

The situation:
1. 2 story townhome (condominium).
2. Late 1970's, cra**y Houston construction. Expansive clays are a local problem.
3. Post tensioned slab on grade.
4. Previous owner installed a very nice wood floor (glue down) on the ground floor (LR, FR, DR, 1/2 bath)
5. Poor site drainage has been a longstanding problem (association finally fixed this year), with significant standing water on patio when heavy rains occur. Water can't get over the slab over the slab (unless the whole neighborhood floods), but can rise to within about 3" of it. We are occassional residents, so we miss most of the heavy rains.
6. Over the 9 years we have owned it, the wood floor has exhibited some shrinakage and discoloration around the joints and very slight cupping in certain areas. It really isn't too bad, but noticable to a trained eye.

I am 99.99999% sure that the slab is cracked and that water (contributed by the standing water on the patio during heavy rains) wicked up through the crack(s) and has caused the wood floor to discolor and shrink.

Now that we have solved the drainage and standing water problem, we will eventually want to do something with the floor. We will likely replace the floor rather than refinishing, although that remains a possibility.

The question is, what to do to with the slab? We will clearly chase and caulk any cracks. Is a moisture barrier worthwhile? If so, any product recommendations?

We will likely change to porcelain tile or stone in the 1/2 bath and maybe the kitchen, but will consider keeping wood if we can solve the water/moisture issues. If we cannot get a high confidence solution to the moisture problem, we will go to tile/stone throughout.

Bruce

Try polyurea spray with water proff coating to solved out the problem.many company providing best polyurea /polyurethane spray e.g ultimate linings,xtremeliners and qwikliner etc.

Concrete will wick moisture even without cracks.  If the issue occurs evenly all over, then this is more likely the case.

Right, it doesn't even need cracks - and the foundation contractor may have poked giant holes all over the plastic barrier before the pour.

If you have the time, and don't mind the appearance, I would let everything set for a couple years before deciding on a solution. Firstly, this will allow you to be certain that the corrections to the water problems have worked. Secondly, this will allow the ground under your home to stablize. Then you will have a better understanding of any structural problems with the slab that you may need to address. Best case, you may only need to do a little refinishing work. Worstcase, you may have to deal with voids under the slab that will need to be stablized before reworking your finish floors.

It has been about 6 months since the drainage was fixed and and it will be at least another year before we return and are in a position to do anything about the floors, so it will be a good test.  We will sell this place in a few years when we build our retirement home, so if we coud get away with a refinish, that would save a few dollars.  Unless you are used to looking for them, the problems we have are not very noticeable.

Because of landscape irrigation, I don't think the drainage work will cause any real problem with soil drying, but only time will tell.  I know there is poly and a good layer of gravel under the slab because we removed an old floor safe at one point.

How can can you detect voids under slabs?  Ultrasonic?  Ground penetrating radar?  Chain drag?

I'm still curious about any firsthand knowledge/recommendations for moisture barriers.

Bruce

Superseal all-in one. I sell a lot of it. you can put wood floor over it and it allows air flow under the floor.

Thanks!

They have an interesting product lineup that I was not aware of.

Bruce

Having been in the foundation repair business for nearly 30 years, I have to say "All concrete slabs in Texas crack!"  If the crack isn't causing a toe stubber or allowing water or insect infiltration, it is not a problem.  I would first ask if you have structural problems like;  doors or windows that don't latch or lock properly, floors that slope noticabily and cracks in the interior sheetrock or exterior brick, rock or siding?  If these don't exist, then you may have a breach of your vapor barrier (the plastic under the slab) or drainage issues allowing water to enter through the weep holes (in the brick) or the void between the bottom plate and slab.  It is possible in an apartment or townhouse to have a roof leak at the common wall that channels water between units to the slab and is causing floor damage.  Notwistanding these possibilities, as others have mentioned, it could simply be moisture wicking through the concrete and a simple underlayment could have protected the wood floors from contact with the concrete and prevented this problem.  I am available to answer any questions you may have regarding Texas foundation issues and can look at homes in Houston, Austin, San Antonio and surrounding areas at no charge. 

Warm Regards,

Gary A. Coffing, Sr.
[email protected]
www.foundationandleveling.com
832-275-7314 direct line

Having lived on and off in Houston since '79, I agree with your statement about cracked slabs!

This particular place has been a bit of a nightmare and we have suffered most of the problems that you describe at different times.

We did have a settlement problem on one corner by the garage door.  It turns out that they built a portion of a support wall a brick ledge (where there should not have been one).  As you can imagine, the sill and the lower part of the studs rotted.  We now have a steel column setting where it belongs.  The ground floor slab has been stable (we have checked elevations) for the 9 years we have been there.

We have also had roof and flashing problems at out party wall, although that has been fixed for a few years.

I remain convinced that the floor problem has been water standing after storms at an elevation higher than the bottom of the slab and wicking up through a crack.  This high water obviously traps liquid water between the bottom of the slab and the vapor barrier and the vapor barrier inhibits downward drying, but I think this is a lesser problem than the crack.   The problem is only on a portion of the floor and is not widespread.  I don't think water vapor by diffusion through the vapor barrier is a problem.  Fortunately, the quality of the concrete used in the slab appears to be quite good.

Hopefully the drainage repairs will solve the problem by keeping groundwater below the elevation of the bottom of the slab.  Time will tell.  It sure would have been nice if the PO had installed a moisture barrier.

Thanks for the response!

Bruce

Bruce,
fourtanetly you have time on your side because before a decision can be made about possible flooring repairs or replacement you are going to need to know if the moisture movement thru the slab has been reduced to an accptable level. For direct glue down wood floor systems you will want to have a moisture reading of 5% or less as measured at the surface of the slab. Most of the wood flooring mfg. have systems for sealing the floors if the moisture content is higher than 5% and i would use the system that they suggest for obvious warrenty issues.
If you want to monitor the condition yourself there are several companies that sell electrinic moisture meters but a decent one that can measure both concrete and wood moisture costs about $300. The low tech low cost method is too cut a piece of either 4 or 6mill clear visquen into a 2'x2' square and tape all 4 edges directly to the floor. Leave it in place for 24 hours and observe the amount of condensation that accumulates under the visquen. I would do this in an area that appears to have no damage and use that as a base line for comparrison to the same test done in an area that is showing signs of moisture damage. While this does not give an actual moisture content reading it will give a gauge on moisture movement