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wonderboard scratch coat for stucco

eleeski's picture

We are building a ski cabin. The schedule is running behind and we have not yet started to stucco the exterior. I am worried that it is too cold to stucco conventionally. Has anyone had experience with hanging wonderboard instead of the usual wire and mud scratch coat. Is the tarping and heating we will have to do still cheaper than hanging wonderboard? Will the wonderboard hold up well?

Thanks, Eric

(post #79856, reply #1 of 17)

Do you mean Hardiboard siding? Wonderboard is a cementitious backer board that's usually used as a substrate for tile. If you mean that you want to know how difficult it would be to hang hardiboard lap siding instead of doing stucco, then I did one last winter. I live in Ohio where we had a very mild winter. We started the mastersuite addition last October, and finished in january. I definitely under bid the siding part of the job. If I were to do it again, I would use my Malco Hardiboard siding shears instead of cutting the stuff with a masonry blade on my circular saw (too much dust!). the material is very brittle, and will break if not carried properly. Besides that, they have installation clips that will hold the siding at the perfect reveal. It's heavy, hard work, but the material is tough, acced lpts paint well, doesn't warp, and is uniform.

Good luck with your project. I used to live in Telluride, so I can't tell you how jealous I am!

(post #79856, reply #2 of 17)

Actually I am trying for a stucco look. There is a Hardi stucco panel but I am skeptical of the seams. Maybe it is best? I was thinking wonderboard as I have used it for some overhead stucco and some small details with good results. I used thinset and tape for the seams and applied a color coat over it. But a small job where the material and labor is less than the setup is different from a whole house.

And I don't want the synthetic foam stucco - I like the fireproofing characteristics of stucco or wonderboard. Plus it's already too cold for elastomerics. We did an elastomeric roof during the heat wave in California last week and it barely kicked off.

Across the parking lot from Squaw Valley is a great location! But it's getting cold.


(post #79856, reply #3 of 17)

I've had better luck with Denseglass Gold for exterior decorative stucco applications rather than harder substrates such as hardibacker or wonder board. My favorite is still expanded wire mesh and real stucco but the dense glass does fine in a pinch so long as you tape the joints with fiberglass mesh tape and skim them with a fiberglass surface bonding cement such as Surewall or equal.


"You cannot work hard enough to make up for a sloppy estimate."


"You cannot work hard enough to make up for a sloppy estimate."

(post #79856, reply #4 of 17)

Hey eleeski
Okay, I live in the tropics and don't deal w/ cold....but we do all stucco and cement buildings.
My experience is with Durock, a tile backer cement board. I have great luck with durock, tape and seal all seams with durock cement or any of the elastomeric coatings. (Accrocrete, Total wall, Dryvit, STO etc.) Then put on a finish coat of the elastomeric, Never needs painting, very fire resistant, water resistant etc. I do know you need a few days of no freezing of the material till it cures.....other than that it is a great exterior finish in most climates.
It is heavy stuff but covers walls quickly.

(post #79856, reply #5 of 17)

Thanks all.

Any ideas of costs vs stucco? Also it is already too cold for elastomeric. How will densglass survive the winter exposed? Durock vs wonderboard, is it just a cost issue? I'm pretty sure the durock or wonderboard will do well over the winter - it might not look great until we finish it in the spring. But grey is an acceptable color for a few months. Can I just paint on the elastomeric or do I need the fabric/mesh as part of the elastomeric finish?


(post #79856, reply #6 of 17)

You can stucco in awfully chilly temps by working under tarps with lots of heat.  I'd be more concerned about going with an unproven method and having to deal with major headaches rather than the cost and effort to tent the exterior.

Stucco guys in the colder states are used to these kind of things and you might even hire a local to tent it or at least rent his equipment for a spell.

Call your hvac guy and ask him to save an old propane furnace that you can retrofit to heat the space without fumes. 

I'm not saying it won't work, but it seems that a heated wall structure expands and contracts much differently than smaller decrative areas of stucco that the wonderboard has been used for successfully.

Best of luck and let us know how everything turns out.


Beer was created so carpenters wouldn't rule the world.

If I could edit my location it would say I'm now in Reno :-)

(post #79856, reply #7 of 17)

I agree....tents are EZ.

The tents don't really have to be 100% sealed. It doesn't take much effort to keep the mud from freezing. It's already throwing off a lot of heat itself.

FKA Blue (eyeddevil)

(post #79856, reply #8 of 17)

Thanks for the input. I feel better about tenting and conventional stucco.

When considering options we started doing some cost comparisons. Maybe my stucco bid is too high but the wonderboard might be less expensive. Does anyone have experience with the time (cost) needed to cut and hang wonderboard and tape the joints. And will a conventional color coat cover the wonderboard without too much other prep on a large wall?

As always, it all boils down to time and money.


(post #79856, reply #9 of 17)

Hi E
I'll chime in again,
Here we tape and seal the joints as flush as possible and then put Total Wall with integral color right on the board without mesh. On my own place I used it over concrete and it looks great after 6 yrs.
Good luck with the weather
If you feel like it, durock will hold up well over winter, but I would at least tape and seal seams so you won't get freezing water behind it
By the way- here in the tropics we use Stainless Steel bugle head screws, it won't get rust runs thru the material if there is any moisture. Screw it on similar to sheetrock

(post #79856, reply #12 of 17)

I'd often wondered if this approach would be worthwhile. I love the appearance of stucco. I can see how it'd be a cost-effective DIY approach.

Just scratching the scratch coat sounds like a pain in the ####, let alone spreading it.

(post #79856, reply #10 of 17)

My last house was a tudor style with stucco and fake half timbering which was poorly flashed. I did an addition on the house and had to replace a lot of the existing stucco around the "timbering".

I used Durock in the fashion you describe instead of lathe and a scratch coat primarily because I was working by myself on weekends and this seemed less labor intensive. Durock has specific details for this application on their website. I was by there this summer visiting my old next door neighbor and it all appears to be holding up fine. The stucco looks fine other than my color match was not perfect (but not too bad, either). It's about 12 years old at this point.

I say go for it.



I was born in a crossfire hurricane..........shooby dooby do

Edited 10/28/2007 5:14 pm ET by seeyou

(post #79856, reply #11 of 17)

Wow, more good info!

The Total Wall looks very easy. At least I won't have to pay a huge premium - and I might save a bit!?

It sounds like either way will work. Now off to to see if there is a strong trend to watch for. Truckee had the low for California the last couple of days. I hope the garage pour on Thursday kicked off OK.

Thanks again all for the help.


(post #79856, reply #13 of 17)

I had a wonderboard salesman approach me and tell me the same thing - use it as a substrate for stucco color coat - tape the  joints with fiberglass mesh and ? (pourstone?), then color coat.  I wondered if this thread would bring any examples out.   Got any pics of the job?

 “Good work costs much more than poor imitation or factory product” Charles Greene

(post #79856, reply #14 of 17)

Got any pics of the job?

Not digital. I'll have to dig them out and scan them and I'm busy as hell right now so it's not likely to happen. Sorry.

If I ever have to personally do anymore stucco, I'll repeat the process. I hate working with wire lathe and it seems to be the point of failure in most of the stucco problems I've witnessed. Of course water infiltration was the culprit.


It takes a big man to cry, but it takes a bigger man to laugh at that man. - J. Handey

(post #79856, reply #15 of 17)

Probably couldn't tell a lick of difference from reg. stucco from the pics anyway!  Glad to know it worked out.  Did you tape the joints at all?

 “Good work costs much more than poor imitation or factory product” Charles Greene

(post #79856, reply #16 of 17)

Probably couldn't tell a lick of difference from reg. stucco from the pics anyway!  Glad to know it worked out.  Did you tape the joints at all?

No you couldn't and still can't. I think I took some progress pics, though, but I can't remember. I taped with mesh tape.


It takes a big man to cry, but it takes a bigger man to laugh at that man. - J. Handey

(post #79856, reply #17 of 17)

An unseasonable warm spell hit California and we were able to get the stucco done conventionally. I now see why wonderboard is not the base of choice for a stucco contractor. With a large crew of really hard working guys they were able to finish a fairly large house in a day (the really warm one)! OK the wire and paper took 2 days and the scaffold another but it was still really fast. Color coat took another day.

Wonderboard could work quite well but I doubt a crew could do the house in a day (or four) and the color coat would still take time. Of course for a guy with a small crew and a small job wonderboard would be the ticket.

As far as advancing knowledge with either cold stucco data or wonderboard results, I wasn't very useful. But the exterior is done before the snows and it looks great. Thanks all for the input.