Post Tension slab cracks

Hello all -

I am very concerned about the foundation of my home in Houston, TX. It was built in Dec of 1993 by Lennar and we bought it in 1998 from the original owners. When we first looked at the house, we noticed a few cracks in the sheetrock around a column and one on a bump-out over a window in the kitchen. We were told they were just from bad tape and float in the sheetrock. We were in our early 20’s, this was our first home and we knew nothing more then the inspector told us - we had the items fixed and bought the house. The door in one of our bedrooms has closed by itself since the day we bought it - we’ve always had to have a door stop in front of it to hold it open. However, we haven’t had any issues with doors or windows not closing/opening.

12 years later, the cracks that were fixed have re-emerged and gotten worse. The area above the column has actually split on either side at the top. About a year ago I noticed a hairline crack in the foundation below our dining room window. A month ago, I could no longer take the worry and has a structural engineer come out. He confirmed that there is a crack in the slab - it goes all the way across the dining room and living room floor to the other side below another window. Along this line is where the ceiling cracks are above the column. There are also 3 more hairline cracks on the same side of the house and our front porch is buckled a little (although he thinks that’s from a tree to close to the house). He took elevations and he said since slabs are rarely ever exactly level, it’s hard to know how much movement there has really been. There is variation all over the house with the lowest being a -.7.

We knew we had a drainage issue in the backyard (it always stays wet) but never knew it was a big deal. Our front yard is sloped downward to the street so it is always dry (our grass dies every summer no matter how much we water it). He thinks if we can solve our drainage issue (with gutters and french drains) that we can stop the movement. My mind is going crazy imagining waiting and my whole house splitting in 2 one day.

My question is - how long should we wait? The cracks are all hairline - I can’t fit my fingernail in them, although the major one has grown wider in the last year - but still not able to fit a penny in it or anything. I’ve read that post tension is made to resist movement but not cracking - ie it will still crack but it will withstand and hold the foundation to prevent sinking in one area versus another. If this was your house, what would you do? Should I not be concerned?

Thank you so much,

Remove the tree.

Having been born and raised in Texas, graduating from Texas A&M University, and living in Houston for five years, if it were my home, I wouldn’t worry about it too much. Patch the cracks as they appear. Houston has a lot of red and black clays, and any structure is going to react the the expansion and contraction of those clays as they get wet and dry out.

What did your engineer recommend?

With this year’s prolonged drought many houses that never showed evidence of foundation movement before experienced cracks and movement. I saw numerous houses where the soil had shrunken so that I could fit my hand between the dirt and the side of the slab. With the expansive soils that we have around Houston, it’s important to maintain even moisture levels all the way around the perimeter of the home and throughout the seasons of the year. Do you have an irrigation system around the perimeter of the house and do you use it to maintain consistent soil moisture levels?

It is very common for houses in the Houston area to have hairline cracks. The hairline cracks by themselves are generally not cause for concern unless you see significant gaps opening up, displacement across the crack or excessive spalling at the crack. Significant movement will typically cause several other signs of distress in the structure.

If the structural engineer did not indicate that you had cause for immediate concern or recommend foundation repair, I would not worry too much about it. Did he give you any specific advice regarding foundation maintenance or repairs?

I would suggest the following: 1) Keep the diagram that the engineer created with your foundation elevation readings. You can take fresh elevation readings in the future and compare them to the original baseline to determine if there has been subsequent movement, how much movement and what areas have moved; 2) Implement any recommendations that the engineer may have given you to help maintain foundation performance (e.g., tree removal, gutters, drainage, etc.); 3) Maintain consistent moisture levels around your house and through the seasons (watch for signs of the soil pulling back from the foundation in dry seasons and water more when needed); 4) Monitor any potential signs of distress (i.e., catalog and photograph known foundation cracks, brick cracks, sheetrock cracks, frieze board separation, crown molding separations, etc. so that you can compare for changes over time.

Relax. If your engineer didn’t tell you that you needed to worry, then don’t sweat it. Houses are dynamic, they all move some throughout the seasons. Mitigate any detrimental conditions and keep an eye out for significant stress indicators (the house’s, not yours).

Thank you all for responding! The engineer recommended implementing gutters around the back as well as a swale (although we haven’t found any landscaping company that wants to do it - they all think we can solve the drainage issues with french drains). Then he recommended we take pictures of all the areas and wait about 6-8 months to see what happens.

The reason I am worried is because I can literally see the crack all the way across the house when I pulled the carpet up. Is it normal for it to crack across the entire slab? How long do you wait - when the slab crack becomes large enough to fit a penny in? When there are more signs of distress inside the house? What if there are other cracks going across the slab - would that make it worse?

Thank you all - for me not worrying is impossible!
Amy Stephens

I have seen products that can be fixed across a crack and attached to the surface at each end. Measurements are sometimes printed on the surface. If movement occurs, the piece will break and the amount of movement can be seen.

I have also seen using something like a glass slide for a microscope with each end attached with epoxy.

A product of this sort could be checked periodically to see if any movement has occured.

To help maintain moisture consistency around the foundation, you can use a landscape drip line placed 2-3 feet from foundation and attached to a timer to work automatically.

Good luck,

Go for the swale if it is feasible for your lot. Properly contoured surface drainage is superior to a band-aid fix. There are landscapers around who do good drainage work.

It’s not uncommon for the crack to extend all the way through the house and it may never open up. The post tensioning will typically keep it closed up tight (each of those tendons has about 30,000 lbs of tension on them). There is no hard and fast rule for when foundation repairs are needed, individual opinions can vary widely (always get an opinion from an engineer rather than a foundation company that has an interest in selling you repairs). A hairline crack is typically not cause for concern.

Chuck - do you have a structural engineer you recommend since you are in my area? I am starting to worry about the crack again and am wondering if I shouldn’t get a second opinion. We did have gutters and drainage installed in early March but I can see the crack has opened up a little more. Should we seal it to prevent moisture/bugs from entering and if so, how?


Hi Chuck - Since you are local to me, do you have any structural engineers you recommend? I believe the crack has opened up a little and I’m starting to get worried again. Maybe I should get a second opinion? We did have the gutter and drainage installed in early March, but should we seal the crack on the outside of the slab to prevent moisture/bugs from getting in? If so, how?