No-Crack Stucco

[Gregg Block]

I'm a general contractor in Sacramenton Ca. I have been involved in residential construction for over 30 years now. I have used dozens of different stucco subs over the years and always get the same answers and similar results. They tell me "Stucco is going to crack, it can't be helped". Sure enough, it always cracks, no matter how I cure it, and no matter what time of year. I beleive the typical mix they use is 3or4:1 stucco sand to Portland cement in a three coat process: Scratch/Brown/Texture coat; over plywood/OSB sheething / 2 layers of building paper/ deformed stucco wire/ nailed 6"-8" at every stud. Cracks every time.
They also say that the smoother the finish/texture the more likely it is to crack (more/bigger). I have taken it for granted that I am going to get cracks, and I tell this to my clients. but I have seen new stucco jobs with a smooth troweled finish, and NO cracks or minimal cracking.
I have called all the stucco suppliers in the area and get no answers there.
Anybody established a good system to reduce or minimize stucco cracks?

[dgbldr]

Re: No-Crack Stucco

I suggest you post this in the Exterior Details section. I'm sure Bill and others will have helpful suggestions.

dg

[Dick Seibert]

Re: No-Crack Stucco

Gregg:

I've always had cracks, and they are really obvious on the smooth "Santa Barbara" finish. I do like you and tell my customers in advance, because of the cracking problem I try to talk them into a "Sand Finish", the "Texture Finish" is too "tract-house-like" so try to steer them away from that, the heavy "Dash" finishes only look good on certain architectural styles but they cover cracking pretty well.

All I do is make the plasterer come back and do a "Fog Coat" on the structure, it goes on quick with a "Hudson Sprayer" and most plastering contractors will do it for nothing when you complain about the cracking. As an Industry Expert I see lots more cracking when OSB is used, when the water overwhelms the weatherproof barrier the substrate gets wet and the OSB swells up to 150% of it's original thickness and cracks the stucco. All I can suggest is to always use plywood and not OSB, then cover it with #30 felt *and* Two-Layer Super JumboTex Grade D paper. That should keep most of the water off the plywood, comply with code, and if the substrate does get wet on the weather side plywood doesn't swell like OSB.

but I have seen new stucco jobs with a smooth troweled finish, and NO cracks or minimal cracking.

Stop and find out who the plasterer was and ask them, then post the answer here, I'd sure like to know their secret!

[denboy1]

Re: No-Crack Stucco

Gregg:

Everyone says "stucco cracks". True to a degree but there are strategies. You're also in a market that is traditional-stucco oriented with no exceptions. Bet the line went dead when you asked. Here's a short list of things I can think of:

Builder Strategies
1. Gap your wood sheathing 1/8" min to 1/4" max. Stucco cracks when the wood expands and has nowhere to go.
2. Put expansion joints at floor lines with 2x joists and gap the sheathing. A house can shrink 3/4" when it dries out.
3. Load home with drywall before stucco. Preferably install it.
4. Double check straightness of studs where you're putting cabinetry or other objects that could straighten out the wall.
5. Schedule application toward the end of the project. It's a Division 9 material after all.

Stucco Applicator Strategies
1. Lath rather than wire - good luck in CA
2. Don't run lath under control joints
3. Allow some time between scratch, brown and finish coats.
4. Fog the wall

Improve your Stucco
1. Add fibers to the mix
2. Add acrylic to the mix (don't fog when doing this)
3. Skim with EIFS base coat & mesh
4. Elastomeric acrylic finishes

[AZ Contractor]

Re: No-Crack Stucco

Are you guys loading the roof with roofing materials and allowing the building to settle at least 2 weeks before you stucco?

After your house wrap and before your lathe are you using 1" foam?

[AZ Contractor]

Re: No-Crack Stucco

Gregg:


2. Add acrylic to the mix (don't fog when doing this)
3. Skim with EIFS base coat & mesh
4. Elastomeric acrylic finishes

Doesn't sound like you are allowing your homes to breath.

[denboy1]

Re: No-Crack Stucco

Andre:

#2 & 3 breathe fairly well. Everyone associates EIFS with slow to pass water vapor. It's the foam, not the base coats or finishes.

You've got a point with #4. Elastomerics in general don't allow as much water vapor transmission. But most aren't a vapor barrier. It's the "hail Mary" of coating lines

I'm not familiar with the stucco habits in Sacramento, but in LA these ideas are greeted with blank stares. It's cement stucco and perhaps a coat of paint.

As a start, fog the wall as DS said.

[Kgphoto]

Re: No-Crack Stucco

How many wait two days between scratch and brown and 7 days between brown and finish coats?

I always do corners and around penetrations with expanded diamond lath. I only do one or two walls at a time, though and so far,they haven't cracked yet.

[Gregg Block]

Re: No-Crack Stucco

Thanks for all of your responses.
I have previously incorporated most of the suggestions, but you have given me some ideas that I will try on the future.
I do remodeling exclusively. Typically 50-100 yr old homes. I usually remove 100% of the existing stucco or siding, install new widows & doors, minor framing changes, like adding on a room or new window/door opening. So framing shrinkage is probably not a huge issue.
Roofing and drywall are always on prior to lath.
I wait a minimum of 3 days between coats and even weeks if I am allowed.
I always keep the fresh stucco damp between coats: Regarding this point, I have tried keeping it soaking wet; keeping it slightly damp; saturating it-then letting it dryout-then saturating it again. What's the recommended procedure here? I would think that the soaking-then-drying process would cause cracks.
My cracks usually show up after the brown coat and keep increasing in size and numbers for weeks, even months after the job is done.
I like the idea of plywood vs. OSB sheathing and I probably should be gapping the joints more than I have. I also like the diamond-lath-at-the-comers idea. That's where most of my cracks show up.
Acrylic admixtures, and fibers I'm familiar with, but the term EIFS base coat does not ring a bell.
Getting any of my stucco contractors to try any new technique or technology is like pulling teeth.
One other interesting thing.
I did a complete re-stucco on a home. To save cost, the owner elected to simply color coat the garage rather than remove and re-stucco it. When the house was ready for the color/texture coat, the stucco-crew fiberglass-taped all the garage cracks and put an acrylic bond-coat on 100% of the existing garage stucco. They then colorcoated both garage and house the same. Months later I went back and the house had some pretty obvious cracks at all of the walls, but the garage was perfect, no cracks, NONE!

Thanks again.

GB

[Russ Grassa]

Re: No-Crack Stucco

Im a plastering contractor in San Diego and informing customers of the likeliness of cracks in the final product is part of the job. People ask me all the time "what can we do to eliminate or at least minimize cracking in the stucco?"

Most of the answers you have all mentioned in this thread already. However in my opinion the best method of combating stucco cracks is a Crack Isolation system. Surprisingly enough, more and more owners are willing to pay the higher cost for the significant crack reduction.

Omega Crack Isolation http://omega.omega-products.com/pg--...on-System.aspx

[Ted S.]

Re: No-Crack Stucco

I'd recommend Bondo with a good primer.