Why is new Stucco cracking so badly?

flyingflowerSeptember 25, 2008

We just replaced an old window with a new one. After it was installed the contractor applied stucco around the window frame to blend in with the existing stucco wall. It started cracking the day he left and just got worse. This has never happened with other stucco patches we've done in the past. Anyone know what could have caused it? He's telling us to go buy stucco caulk and fill in the cracks.

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Judging by your picture,(tell me if im wrong), it looks as if that application is the scratch/ brown coat with no stucco top coat,(typically 1/4" thick). After the lathing/underlayment, a cementious based scratch coat is follwed by a brown coat of the same material that is brought out to a level to match up to the existing. The scratch/brown coat will crack normally and is important for it to sit for at least 3-4 weeks in most cases before the stucco color coat is applied. This allows the cracking, again normal, to happen as much as it can and wont follow through to the color coat. You can caulk with an elasomeric caulking after "v-grooving" out the cracks, but i would let it set for the 3-4 weeks and top coat with stucco mix top coating, then paint to match.

Cracking can also occur due to a "too dry" mix drying out too fast,(hot weather), as well as improper install of the lath wire.

If you go the top coat route, while waiting for the scratch/brown coat to "cure and crack", periodically a.m. & p.m wet the area down with water, Give it a good soaking with a garden hose.

    Bookmark   September 25, 2008 at 2:06PM
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It appears that your patch has been scrubbed off to the level of the existing finish.
Call the contractor and have him correct this.
This cracking is not normal and is from too much water in the mix and/or the product applied, if single coates without the benefit drying time,(1 day scratch to brown, 14 days brown to scrub,color coat).
Using hy-early cement allows for the application of the scratch and brown coat in a single operation.
The use of an exterior speedy patch product will allow you to either paint or scrub in a matter of 1 or 2 days.
If properly applied.

    Bookmark   September 26, 2008 at 1:04AM
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Have to respectfully disagree with you,snoonyb. The importance of the waiting period before top coating is to allow the scratch/brown coat to crack which is normal. The "normal" cracking is hairline or a tad more than hairline but not talking about any serously wide or deep cracking here. By waiting and allowing for the cure/settling of the scratch/brown coats, the cracking typically wont follow through to the top coat.

The o.p hasn't responded as to wether this is actually the scratch/brown coat shown, it's assumption on my part. If not, that cracking is a different animal and regardless, either way should be addressed and fixed by the contractor as you stated.

    Bookmark   September 26, 2008 at 10:09AM
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I've been forwarding your responses to my husband, thank you so much for your detailed answers.

What the contractor did was put on one scratch coat. Then he let it dry for 3 days. Came back and did the final coat. He told DH there was no need to hose it down with water. He says he used the better stucco product that he buys from Home Depot.

DH is so angry this happened, he's going to use a saw and cut the final coat out, let the base coat cure and then bring the contractor back to redo the final coat (since DH is not good at smoothing out stucco). Contractor tried to weasle out of it by telling us to fill the cracks with stucco caulk but DH isn't convinced that's going to work over the long term.

I told him to let the contractor cut the stucco out but he's lost all faith in this guy now and wants to do it himself. I don't think he trusts him to cut it out without damaging the window given how sloppy he was prepping for the project to begin with. DH normally does a lot of our construction projects so whenever someone we hire botches things up he cusses for a day or so and then fixes it himself!

    Bookmark   September 26, 2008 at 12:53PM
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You can disagree all you want.
I've been plastering for almost 40yrs and my stucco does not crack.


"What the contractor did was put on one scratch coat. Then he let it dry for 3 days." Thats fine.

"Came back and did the final coat."
And there-in lies the problem. That material is not designed to be applied in thick coates, as you can see, and hosing it down may have washed it off.

As I said before, with the proper material, stucco can be applied in 1 or 2 coates.

    Bookmark   September 26, 2008 at 8:55PM
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I owned a stucco home in Calif. and watched several being built around us. I never saw cracks form in our home and if they did on the newly built homes, the owners had it repaired immediately due to the worry & horror stories of leaks/rot once the rainy season started.

Hairline cracks near window & door corners may be seen due to settling but I wouldn't call those cracks on flyingflower's home hairline.

    Bookmark   September 26, 2008 at 11:25PM
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I learned the trade when there were 4 inspections, in the toughest town in So.Ca., Long Beach, and if you failed an inspection at any stage, the 17 day clock started over.
It didn't take many short paydays before you perfected your trade.

    Bookmark   September 27, 2008 at 1:42AM
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We are in the mojave desert. Maybe it's a geographical thing, but i have never in my over twenty years not seen hairline cracking on the scratch/brown coat and when let set the mandatory 30 days ,(in our county), rarely see the cracking follow through the top coat. Cracks over openings that are considered the weak point of a structure are usually addressed by reinforcing with rib lath wire at those corners to help prevent cracking.

    Bookmark   September 27, 2008 at 11:53AM
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The underlayment/lath/flashings are what keeps a structure dry along with the proper drainage plane by way of a weep screed. Water or moisture is going to condense behind the scratch/brown coats despite cracking. A faulty install of the underlayment/flashings/lath/screed is what will lead to rot of the framing members, not water through cracks. The use of a double ply underlayment is helping to reduce this moisture as the scratch coat has a tendency to stick to the first ply that causes the condensation. This even happens in the low humidity of the desert, so double ply is a good practice.

    Bookmark   September 27, 2008 at 12:12PM
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