Hairline stucco cracks at windows

[RichardAIA]

The exterior of a new home I designed was recently finished with an integral-color stucco coat. Virtually EVERY window has long hairline cracking at the corners, extending down and outwards at approximately a 45 deg. angle, down to the weep screed. (One-story house).

They were doing the finishing on a very hot day, and I doubt did any fog coating. The owner hasn't said anything yet, but I suspect it won't be long before he does.

I am trying to assess what realistic expectations should be, and whether the stucco company may have screwed up. Obviously SOME hairline cracking is to be expected, but EVERY reentrant corner?

Has anyone found any solution to this issue other than painting? Any insights appreciated.

[Allan Edwards]

Has anyone found any solution to this issue other than painting? Any insights appreciated.

What size cracks are they, and how visible are they? I have an integral color stucco house I'm doing, there are very small cracks, they show up more when it's wet. I think with integral coloring and no or minimal control joints, which is what architects I work with want, there will be some cracking. But boy, it's a lot better look than elastromeric painted stucco.

[NW Architect]

They need to have put an diagonal piece of lath (as a lath overlay) on each corner to change the stress dynamics a bit. Not done unless spec'd. Proper control joints - which would have been near those corners are the better response.

[Dick Seibert]

Richard:

That's strange, cracks going up and down at the corners of windows and doors *usually* indicate settling, but I can't believe that with the foundations we put in here that you would be having any settling, you do have an engineered pier and grade beam foundation don't you, PTSOGs can do it too? If you've got the time I'm going to be in your neighborhood Monday, I'd stop by and we could take a look at it. If it is due to the heat, which I doubt because those kinds of cracks usually run vertically, the solution is a fog coat after the cracks have stopped opening, fog coats are cheap and quick, I'll bet the plastering contractor would do it without argument or cost to solve the problem. The lath on the corners NW mentions I seldom see on exteriors here, we do it all the time on interior plaster. I see cracking stucco all the time on the Southern exposure when OSB is used, but never with plywood sheathing and never diagonal at the windows. Whatever you do don't paint, you'll seal mositure in the walls and you'll really have problems.

[AZ Contractor]

They are there because of settling and can be prevented to a degree by:

1. Loading up the roof with all the materials and let it sit a few weeks before finishing the stucco.

2. Using diamond lathe in the corners to give the stucco a better base.

3. Making sure the finishers use the correct amount of lime in their stucco mix.

4. Using a fiberglass based first coat.

And be careful with elastomeric paint on stucco. It holds in most of the moisture and doesn't allow the house to breathe.

[Tom Teka]

I think this elestomeric paint is a bigger concern in rainy climates. Down here most upscale homes (2-5 million) have elastomeric paint.

[RichardAIA]

I appreciate all the comments. I doubt this cracking is due to settling, since every window all the way around the house has identical cracking. If it were settling, it would be more localized. The tile roof had been installed for a number of weeks prior. In retrospect, I might have spec'd the diagonal lath at the corners, but I have never seen it done here.

Dick, I really appreciate your offer, but I don't think a site visit would add much at this point. (Also, the project isn't really in my neighborhood - it's in Los Altos.) My guess is that the brown coat was really dry, and combined with a hot day, just sucked all the moisture out of the finish coat too quickly. The cracks are really hairline, and reentrant cracking is a pretty common result, although I have never seen it to this extent.

I agree that an elastomeric coat is to be avoided. With the integral color coat, I don't know how well some touch up troweling would work. I'm just a little unsure of where to go from here if it becomes a problem to the homeowner.

[Dick Seibert]

Richard:

It won't hurt to do a fog coat, the supply house where the plasterers buy their supplies will stock the powder as long as you specified a stock color, is it La Habra?

BTW, do you have a Santa Barbara finish for the color coat? It looks great but shows every crack, before I'll put one on I bring the customer by a previous job so they are aware of the potential for cracking (it doesn't crack more, it just shows the cracks more). If the architect has specified a Santa Barbara finish, the customer doesn't like the cracking and wants to see an alternative I show them a sand finish. I hate texture finishes, they make the house look too much like a run-of-the-mill tract house, but the texture does cover a multitude of sins. I liked a dash finish in the old days when it was hand shaken, the new machine-blown dash finishes look very rough unless that's the look the architect wants.

I'm going down to Los Gatos after leaving Stanford, I can swing by Los Altos on the way if you want to E-mail me the address, but warn the customer that some dissolute looking old man will be coming by (of course that would alert them that something was wrong if they don't already know). I agree that it shouldn't be caused by settling if you are on Pier and grade beam, but if you are sitting on a PTSOG it probably is the cause but there should be interior cracking and sticking doors too, I saw houses cracking all over the place, including angled cracks at window corners with those things, but every engineer I know now puts pier and grade beams under the PT slabs.

[RichardAIA]

Dick,

It's fairly close to a Santa Barbara finish, which doesn't help, of course. I'd like to have a little more discussion and investigation with the GC on the project, and maybe the plastering association, before the dissolute old man (oh, I mean dissolute-"looking", of course) shows up and draws even more attention to the issue. But again, thanks for your offer!

BTW, it's just a plain old one-story house on a spread footing, similar to just about every other house in the area.

[Dick Seibert]

Richard:

Oh, I thought it was a new house, an old spread footing should have settled in by now (absent something strange going on underneath it). Was it a new 3-coat stucco job over the entire house, or was it it patched and a color coat placed over existing 2 or 3 coat stucco? If there is no cracking of the sheetrock and/or sticking doors or windows inside, you can pretty much rule out settling, but I don't buy your hot day theory with diagonal cracks at the windows only. If the cracks are drying cracks a fog coat should fix them, it certainly can't hurt to try. The Lathing & Plastering Institute of Northern California is located here in Lafayette now, I've called them a couple of times when I had problems with a plastering contractor, but all they seemed to want to do is protect the plasterer, but you can try them, it won't hurt and they may assure the owner that the cracking is "normal".

Santa Barbara finish is very desirable, but the customer should be pre-warned that every little hairline crack will be visible. I've had to go back with a fog coat everytime I've used it, now I make the plasterer include it in the bid, but it shouldn't be done until a couple of months after the color coat is applied.

[Diamond Custom Homes]

There will be cracking to some degree, always expect and explain it. Depending on the magnitude the fix will vary. Hopefully it is a standard color.

How new is it?
Does it have fiber in the browncoat?
What ga.wire?
How long between brown and color?
Did the moisture get controlled properly?
No disrespect meant but...are the windows flashed/sealed properly? If water gets behind the stucco to the wood soon after application, that will cause it.

[denboy1]

NW's point on diagonal lath is a good one but diagonal cracking is usually an indication that something is moving. Possible other causes could be tightly butted sheathing or simply tightly butted stucco to window connections.

[Stuccoman]

Was the sheetrock hung before the stucco was done?

Was the interior trim trim installed before the stucco was installed?

Did the basecoat cure before the finish was applied?

[RichardAIA]

There will be cracking to some degree, always expect and explain it. Depending on the magnitude the fix will vary. Hopefully it is a standard color.

How new is it?
Does it have fiber in the browncoat?
What ga.wire?
How long between brown and color?
Did the moisture get controlled properly?
No disrespect meant but...are the windows flashed/sealed properly? If water gets behind the stucco to the wood soon after application, that will cause it.

It's a fairly dark custom color, but supposedly controlled to be matchable in the future. Very new installation. Don't know if there was fiber in the browncoat, but I doubt it. At least a week between brown & finish coats. There has been little to no moisture in that time, so unlikely moisture is a culprit. Drywall and interior trim was installed long before finish coat.

Here's an explanation of probable cause: http://www.wconline.com/CDA/Articles...00000000073752

(Under re-entrant & shrinkage cracks.)

Question is what to do now, though.

[RichardAIA]

If the cracks are drying cracks a fog coat should fix them, it certainly can't hurt to try.

Dick,

I always thought a "fog coat" was essentially misted water, sprayed during the curing process, and done to keep the stucco from drying out too quickly.

How does your type of fog coat work, especially with a Santa Barbara finish? Is it stucco which is troweled immediately after spraying, or is it something else?