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STG · Jun 5, 2008, 06:39 AM

Hi-

I've been reading all the great answers on this site and I've found it very helpful.

But... I'm still quite nervous about some things with regard to my own house. My house is a 1600 square foot, single-story home on a slab foundation. Three sides of the house are brick - the back of the house is siding. The foundation is coated in a stucco-like concrete parch coat. The house is located in north-central San Antonio where the soils are a combination of clay and limestone. The limestone bedrock is about 10 inches below the ground surface.

There is no interior damage to the wall or ceiling sheetrock, all the doors and windows function fine. I've uploaded a PDF with the locations of the issues.

I have hairline cracking in three places that I'm concerned about. The cracks are all about 1/32" in width or less.

Corners

Two of the corners have diagonal cracking running at a 45 degree angle beginning near the corner of the foundation and continuing toward the inside dimension of the foundation. The cracks are well below 1/16" in width and the width the same along the entire length of the crack. Not sure if this is important to mention, but these corner areas are only in the areas of the foundation that are topped in brick (that is, the walls above the areas have brick facing).

Garage

Last night I found another crack in the foundation wall of my garage. The foundation rises from the garage floor to a height of about 24" where it achieves the same level as the floor of the house. There is a hairline crack running from about three from the floor all the way to the actual top of the foundation wall. This crack continues into the concrete under the carpet inside the house for about a 10" length.

I broke out my cold chisel and hammer last night and cleared away the parch coat and a bit of the concrete. The hairline crack in the garage foundation wall runs through the parch coat and into the foundation about 3/4" - and then it stops. I ended up clearing away a V-shaped area of the concrete 3/4" deep at the deepest spot and about 3/4" wide at the outer limits of the "V" (the inner limit was 0" wide). After doing this and satisfying myself that the crack didn't extend deep into the foundation, I sealed up the area I'd chiseled with Quikcrete concrete repair ( QUIKRETE® - Concrete Repair ). I applied this by packing the area with the product and then smoothing it with a putty knife.

At the top of the crack - in the house itself - I chiseled out a bit - and the crack's depth is only about 1/16" at its worst. I left that alone.

The cracks in the corners have been temporarily sealed with the Quikcrete product as well - I've had quotes for repair of that using lathe and a new concrete parch coat.

My questions...

1. Should I be freaking out? I'm losing sleep over this and stressing out constantly.

2. Did I do anything stupid in the garage by chiseling out the crack and patching it?

3. Does the repair that the contractor has told me about make sense?

rtw_travel · Jun 5, 2008, 08:07 AM

How old is the house? How long have the cracks been there? Are they getting worse?

Originally Posted by STG

1. Should I be freaking out? I'm losing sleep over this and stressing out constantly.

2. Did I do anything stupid in the garage by chiseling out the crack and patching it?

3. Does the repair that the contractor has told me about make sense?

1. No. Go to sleep. If there is no leakage during rainshowers, and if your doors and windows open fine, then there are no worries. Concrete will crack due to thermal effects or perhaps a bit of settling. Cracks of the width you mentioned are acceptable. The rebar will hold everything together.

2. No. You can patch it.. but I would only bother if it leaks. Patching concrete will not stop the crack - there are huge forces at play and a small amount of patching compound will not help much.

3. Its up to you. I would only fix it if there is leakage, or if you don't like the cosmetic look. Adding more concrete/ patch coat will only crack again if the slab wall crack is due to thermal expansion.

STG · Jun 5, 2008, 08:15 AM

Originally Posted by rtw_travel

How old is the house? How long have the cracks been there? Are they getting worse?

1. No. Go to sleep. If there is no leakage during rainshowers, and if your doors and windows open fine, then there are no worries. Concrete will crack due to thermal effects or perhaps a bit of settling. Cracks of the width you mentioned are acceptable. The rebar will hold everything together.

2. No. You can patch it.. but I would only bother if it leaks. Patching concrete will not stop the crack - there are huge forces at play and a small amount of patching compound will not help much.

3. Its up to you. I would only fix it if there is leakage, or if you don't like the cosmetic look. Adding more concrete/ patch coat will only crack again if the slab wall crack is due to thermal expansion.

Thanks for responding.

The house was built in late 1995, so it's just under 13 years old. I've been in the house for a little over six years. The cracks in the corners have been there since I moved in. I can't say that they're getting worse... I plastered over the corner cracks when I moved in and became concerned when I saw they'd re-cracked in the same location... noticed it while landscaping.

I don't know about the one in the garage - it may be that I simply didn't see it, since it it's right behind where we keep our trash can and recycling bin.

ballengerb1 · Jun 5, 2008, 09:16 AM

I agree with rtw, hairline cracks like you describe are very common, almost expected, in concrete. Even a small crack in the interior drywall is not a reason to lose sleep. However, if you eventually get doors sticking and windows that do not operate you might need to consult a structural engineer but not at this point.

STG · Jun 5, 2008, 09:55 AM

Originally Posted by ballengerb1

I agree with rtw, hairline cracks like you describe are very common, almost expected, in concrete. Even a small crack in the interior drywall is not a reason to lose sleep. However, if you eventually get doors sticking and windows that do not operate you might need to consult a structural engineer but not at this point.

Thanks a bunch. The comment about the cracking being common and almost expected is especially comforting to read. So far, no issues with doors and windows... so I'll get these patched up for cosmetic reasons.

I should be OK with this, right?

ballengerb1 · Jun 5, 2008, 10:46 AM

Yep, but don't expect patches to hold real well unless you use a patch with some flex like modified thinset.

STG · Jun 5, 2008, 10:51 AM

Please excuse my clueless question...

What's a "modified thinset?"

ballengerb1 · Jun 5, 2008, 10:56 AM

Look in the tile aisle at a home center. It is used to set ceramic tile on none concrete floors like Hardibacker and Wonderboard. It is a thinset which is mortarlike but has some acrylic added to it so it has a tiny bit of flex to it, won't crack so easily.

STG · Jun 5, 2008, 10:59 AM

Great. Thanks a bunch for the help.

STG · Jun 5, 2008, 02:27 PM

One other thing I failed to mention earlier...

The toe molding in the hallway above the faint crack in the floor concrete is slightly pulled away from the sheetrock. It's not damaged and there's no cracking in the sheetrock itself, but it is something I'm curious about.

Is this any added reason for concern?

STG · Jun 6, 2008, 07:37 PM

OK... did the repair.

I contacted Quikcrete's tech support line and asked for a suggested product. They told me that the appropriate stuff is Vinyl Concrete Patcher - a product with 5000psi of compression strength after 28 days of curing. I've applied this product to the crack - it actually looks pretty good.

I did dig out the crack a bit more with my cold chisel before applying the patching compound - found that the crack centered on two pieces of quartz rock in the cement. It appears that the quartz rock did not adhere to the rest of the concrete - and then caused spalling around it... and the hairline surface crack was the result.

Any thoughts on this would be appreciated.

ballengerb1 · Jun 7, 2008, 11:24 AM

When concrete cracks, and it always will crack, it finds the weak spot in the mix nearest the stress point. Sometimes it's the aggregate and other times not, you just never know where. That's why they make seams in sidewalks, they know it will crack and they are try to direct the crack.

STG · Jun 7, 2008, 12:19 PM

There also a number of hairline cracks in the floor surface inside the house, too. I spoke to a guy about them - evidently this is normal, too. These cracks only go down about 1/8" - just enough to make a guy nervous.

I've also found one area of concern on another part of the foundation. I found a half-moon shaped crack in the top of the foundation between two studs. I chipped out more of the crack - and the area wasn't deep - but it did start to give a little. I packed that area up with more of the Quikcrete vinyl patching compound. I think this will be OK.

The answers I've received have been very reassuring and I am appreciative of this treatment for my house hypochondria. :-)