# Stucco over Foam Board?



## buildgreen (Jul 1, 2008)

I am thinking about using 1" rigid foil-faced polyiso foam board over my plywood sheathing and then stucco over part of the house and hardiboard siding over the rest. Are there any issues I should be aware of? My contractor is concerned about the weight of the stucco not being supported by the longer nails that need to go through the foam.


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## clasact (Oct 21, 2006)

What your discribing is the DRYVET system it is not for DIY you have to be compay certified to use it and it expensive.If your dead set on useing some form of it I would talk to one of their contractors


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## mark942 (Feb 2, 2008)

I am wondering if when you say STUCCO you mean what you say? Stucco is a 3 to 4 part system with a cement base product. On the other hand,with your comment about a poly board being a sub straight I to would be inclined to think your referring to a DryVit type system.The difference being is that with dryvit the base is a Elastomeric product. Could you elaborate a bit more?


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## buildgreen (Jul 1, 2008)

*Stucco over foam board?*

Yes, regular 3-coat cement-based stucco, not dryvit.


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## clasact (Oct 21, 2006)

I would think that the weight of three coats 2 skin coats and the stucco finish coat would just pull the form board right off the nails no matter how long the were.If your thinking of this for decorative additions they do make preformed for around doors and windows that is stucco that you can either put into a skin coat or use adhesives on.I am doing a kind of stucco finish on my house also.It includes two part skin coat and then a paint ,roil on ,or trowel on stucco finish it is called con pro flex by conproco but it still requires at least two coverings of skin which I believe would make it to heavy for the foam board to stay put


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## buildgreen (Jul 1, 2008)

*stucco over foam?*

The stucco wouldn't go directly on the foam, there's the wire lathe that would be nailed into the studs through the foam board. It's not decorative. The purpose is to increase the R-value and reduce thermal bridging through the studs.


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## clasact (Oct 21, 2006)

if that the case why not just put the foam under the plywood then your lath on the plywood.thats what I did then your tar paper and skin coat also act as a seal around doors and window and where the seams of the plywood come together.You have to use longer nails to penetrate the foam board and by code I believe the nails for the lath must also be long enough to penetrate to the studs


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## mark942 (Feb 2, 2008)

There seems to be a good point here. But in my mind there is a area between the studs thats got me concerned. With the mesh you have to follow a nailing schedule,and that would include the spaces between the studs. You do not want to skimp on the nailing.Loose (metal) lathe or mesh will result in sagging,which will crack. It has been said by clasact "to put the foam under the plywood then paper over the top" Then go a head and Stucco. I would (If it were my peace of mind) go with that as apposed to having a worry in the back of my head.I know from experience that when I have worries in the back of my head with a project it usually bites me in the butt. Keep a posting of how it goes...................Good Luck........................:thumbsup:


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## MacRoadie (Apr 25, 2008)

What you are referring to is sometimes called a "western one-coat" (even though it's actually 2 coats) system and is used all over California, Arizona, and Nevada.

While often confused with "DryVit" type EIFS systems, a one-coat system is a hybrid between a traditional three-coat system and a barrier-type EIFS product. The one-coat system incorporates a vapor barrier applied over the sheathing (building paper, Tyvec, etc), followed by 1" foam board then lath, then a base coat of portland cement plaster (usually reinforced with fibers) at about 3/8" in thickness (specs vary on this). This is followed by a color coat of about 1/8" thickness. 

The lath is fastened through the foam using staples which are lengthened to accomodate the thickness of the foam board. I've seen thousands of these units and never seen lath fastener withdrawal when the appropriately sized fasteners were used.

http://www.nocsa.org/faq.htm#link2

http://omega.omega-products.com/Files/Download/Omega_OP700_DiamondWallSystem.pdf

http://www.prowall.com/PDF/One-Coat%20Stucco.pdf

As others have said, these are proprietary systems, however, and must be installed by approved applicators. They really aren't DIY products.


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## mark942 (Feb 2, 2008)

:laughing:

Leave it to the west coast to come up with a synthesized version of Adobe.
Good to know MacRoadie ,,,,,,,,,,,,,,,,,,,,, Thanks for the post........:thumbsup:


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## MacRoadie (Apr 25, 2008)

mark942 said:


> :laughing:
> 
> Leave it to the west coast to come up with a synthesized version of Adobe.
> Good to know MacRoadie ,,,,,,,,,,,,,,,,,,,,, Thanks for the post........:thumbsup:


Well, they were using adobe for a year or two before the white man showed up out here, and it seems to have worked out just fine for them...lol

Actually, it is a better product for use in desert conditions. It is a much more flexible product and can handle the extreme temperature swings of the desert (below freezing in winter and over 110 degrees in the summer. You get much less thermal cracking. It also provides extra R-value as well.


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## clasact (Oct 21, 2006)

since I have a couple of pros here that know stucco and the original question has pretty much been answred I thought I would pop this in and see what you thought of the product its called conpro flex you can see moer about it by going to the web site at www.conpro flex .com I am planning on useing it if it ever stops rainning for more then half a day and wanted to get your thought or experiance with it Thanks


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## mark942 (Feb 2, 2008)

Classact,I had to laugh at your PRO comment.Least wise for me.I am no where near a pro,just have had a little expierence with Stucco.By the way the link
you posted doesnt seem to work.I can see from the name, I haven't used this product. Maybe MacRoadie will be able to shed some light on it ?

It has been raining a lot in Pa hasnt it? 



MacRoadie. Built one of my first homes in Cottonwood AZ from Adobe.What a mess it was for us at first. But we asked around and things turned out just fine. I saved the links you posted for a in the near future house that I will be working on..................Thank you once again................:thumbsup:


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## clasact (Oct 21, 2006)

jsut try to search conpro flex to see the web page and tell me what you think.You have worked with stucco products before so an opinion will work too eventhough you havent used it


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## mark942 (Feb 2, 2008)

Clasact.............Just had a little read about the Conpro flex by Conproco Corp. Acrylic base/Mildew resistance and a 1 step process.It all reads good, BUT I am old school and am a hard sell when it comes to new products.I always wait until MIKEY TRIES IT. I did read MacRoadie`s links and from the looks of it they too are similar to the Conpro flex your looking at. Both being good reads, but when it comes to Stucco it has got to be one two three and maybe 4 steps for me. I am thinking MacRoadie would be better to make comment about Acrylic base products. The only other Product or System I have used has been Dryvit. The company(Commercial Building application) I did the work for liked it very much. Myself, it just didn't have the depth that I have come accustom to. Please feel free to let me know how things went for you with the Acrylic products.................:thumbsup:


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## clasact (Oct 21, 2006)

I apreciate your taking the time to read it and comment on it.I wanted to do the DRyvit but they wouldnt sell me the stuff said I had to be a factory trained rep to use it.I went to the local masonary store and they sold me on thr conpro flrx said it would hold up very well in Pa. conditions.I may get the chance to find out someday when it stops raining or I may coat the ark with it:thumbup:


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## dsiemer (Jan 15, 2009)

Since this is a DIY forum & EIFS (synthetic stucco over insulating board) manufacturers/suppliers all seem to insist upon "professional installation" & charging a great deal more than they should, I'll describe my own experiences with it.

Seven years ago I concluded that the fake lapboard siding of my mid-70's era stick-built home here in Eastern Idaho was getting too ugly to paint again & also that it'd be good idea to add some insulation - a perfect EIFS scenario. At that time, 2" thick beadboard sold for about 25 cents per square foot, local insulation shops/lumber yards wouldn't sell their EIFS "systems" to amateurs & the pros were charging about $3.50/sq ft to install the stuff. Since my review of the relevant technical literature (I'm a chemist by profession) suggested that an acryllic-fortified thinset (eg. Walmart's "Versabond" - $15/50 #sack) would probably work just fine as a "stucco" I decided to give it a try: I stripped off the old lapboard siding (subsequently ripped into stove-sized chunks & used as home-heating fuel), tacked up full-sized sheets of 2" bead board with some 4" twisted-shank galvanized nails & homemade galvanized steel washers (approx 1.5 inch squares with their corners turned down to bite into the foam), stetched plastic-coated fiber glass stucco mesh over the foam & tacked it down with more nails/washers (into the studs), & then troweled on an approximately 1/6" thick layer (one bag/sheet) of white "Versabond" (just one layer). Since I didn't know where to put expansion joints, I didn't bother with them 'cept at the corners - which are covered with 3" by 2", L-shaped, white painted galvanized steel flashing nailed to the wall on its 3" side & free to slide on the other. Since I didn't want to change (or move) the original windows/doors, the foamboard running along their tops was slightly undercut to form a drip edge & that under their bottoms tapered off at 45 degrees to facilitate rain runoff. 

The bottom line is that this "system" has worked just fine - no cracks (my biggest seamless surface/wall (no windows, etc.) is 30' by 10' & the stuff has undergone roughly a thousand freeze/thaw cycles since it was installed), my house is significantly quieter (less road/wind noise) & much cheaper to heat/cool, it doesn't have to be painted, "dings" are easily fixed - and it cost me less than 30% as much as a "pro" would have charged. Another handy feature is that you can make up your own trim etc by carving a thin sheet of foamboard into whatever shapes you like (cover with a contrasting colored stucco).

The downside is that you can't sue anybody if you screw up.


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## dsiemer (Jan 15, 2009)

Since this is a DIY forum & EIFS (synthetic stucco over insulating board) manufacturers/suppliers all seem to insist upon "professional installation" & charging a great deal more than they should, I'll describe my own experiences with it.

Seven years ago I concluded that the fake lapboard siding of my mid-70's era stick-built home here in Eastern Idaho was getting too ugly to paint again & also that it'd be good idea to add some insulation - a perfect EIFS scenario. At that time, 2" thick beadboard sold for about 25 cents per square foot, local insulation shops/lumber yards wouldn't sell their EIFS "systems" to amateurs & the pros were charging about $3.50/sq ft to install the stuff. Since my review of the relevant technical literature (I'm a chemist by profession) suggested that an acryllic-fortified thinset (eg. Walmart's "Versabond" - $15/50 #sack) would probably work just fine as a "stucco" I decided to give it a try: I stripped off the old lapboard siding (subsequently ripped into stove-sized chunks & used as home-heating fuel), tacked up full-sized sheets of 2" bead board with some 4" twisted-shank galvanized nails & homemade galvanized steel washers (approx 1.5 inch squares with their corners turned down to bite into the foam), stetched plastic-coated fiber glass stucco mesh over the foam & tacked it down with more nails/washers (into the studs), & then troweled on an approximately 1/6" thick layer (one bag/sheet) of white "Versabond" (just one layer). Since I didn't know where to put expansion joints, I didn't bother with them 'cept at the corners - which are covered with 3" by 2", L-shaped, white painted galvanized steel flashing nailed to the wall on its 3" side & free to slide on the other. Since I didn't want to change (or move) the original windows/doors, the foamboard running along their tops was slightly undercut to form a drip edge & that under their bottoms tapered off at 45 degrees to facilitate rain runoff. 

The bottom line is that this "system" has worked just fine - no cracks (my biggest seamless surface/wall (no windows, etc.) is 30' by 10' & the stuff has undergone roughly a thousand freeze/thaw cycles since it was installed), my house is significantly quieter (less road/wind noise) & much cheaper to heat/cool, it doesn't have to be painted, "dings" are easily fixed - and it cost me less than 30% as much as a "pros" would have charged. Another handy feature is that you can make up your own trim etc by carving a thin sheet of foamboard into whatever shapes you like (cover with a contrasting colored stucco).

The downside is that you can't sue anybody if you screw up.


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## Tscarborough (Mar 31, 2006)

What you can do yourself with a self-designed "system" is one thing. What a supplier/manufacturer can and should sell you or even tell you is a different kettle of fish.

I do not advise customers on methods of construction, period. If you know what you need, I am more than happy to help you, but if you do not, and can not estimate quantities required (from stated coverages on literature), then you will probably not be satisfied with your shopping experience with me. I do not even give contractor references except for commercial construction, and then only on faxed company letterhead requests.

This is a direct result of litigation.

Online, I do not mind giving advice, since there is no legal recourse. 

To the OP, one coat systems work well, but you must realize that any deficiency in application and detailing will cause damage that is not readily apparent (but very, very expensive to remediate), often for many years. This is especially true for areas outside of the Southwest.


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