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I want to build a play house for my kid and and fool around at the same time. Is is possible to use portland cement stucco over expanded polystyrene (the white stuff) Please bear with me. I am a painting contractor by trade, so I don’t really know anything about this stuff. The questions I have are these. What mix should I use? What about adding lime, laytex of some sort, pool mix? My instinct is to tape the joints with mesh. Knock on a coat, scratch it up and let it firm up. Then come back with another coat and call it done. Will portland stick to styrofoam? Do I need glue? Will lime increase plasticity? What ratio do I use? Single or double hydrated? I want to mix my own because I’m just that kind of guy. Cheap. Does pool mix (marble dust) decrease the breathability of the stucco? What is the difference between marble dust and whiting? Any tips I should know? Thanks in advance.
Matt
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matt,
If you add acrylic to the stucco it will bond to the styrofoam pretty well but you must keep the coat fairly tight. That is basically what most of the EIF systems are acrylic, fine sand and Portland. The acrylic makes it sticky, flexible and tough so it can go on thin. DRYVIT, STO, Pleko, Senergy are examples of EIF Systems. The EIF Systems use fiberglass mesh reinforcement. If you want conventional stucco and if you want this to last you should use stucco mesh or even chicken wire. Nail it up over the foam. If you are using only foam then of course you have to hit studs. If you have sheathing then nail every 8 to 10 inches. Use one bag of Portland: 1/3 -1/2 bag of lime and 25 gallons of sand for conventional stucco. Scratch it and rake it, let it set brown it float it and then you can put a finish coat on it if you like. I think marble dust and whiting are the same thing whiting might be more finely ground. I don't know about the breathability of pool finish. I do know that it is finished to be very dense.
*Why the foam? Conventional 3-coat stucco will go up readily over sheathing (plywood or OSB), or directly onto studs. In either case, two layers of builders felt go on first, then the stucco wire lath, then the scratch coat (3/8" thick, keyed into the lath), then the leveled-up brown coat (also 3/8") and finally the finish coat at about 1/8". When stucco is applied directly to the stud framing, taut wiring is fastened horizontally to the studs at about 12" centers, to brace the lath from pushing in when applying the scratch coat. If doing this, do wire, then felt, then lath and scratch coat. An excellent resource is the Portland Cement Plaster (Stucco) Manual (Portland Cement Association, Skokie, IL). It is a 50 page pamphlet loaded with great information. If you want to mix your own, fine, go to it, they show you all the recipes. Good luck! Tell us how it turns out.
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I want to build a play house for my kid and and fool around at the same time. Is is possible to use portland cement stucco over expanded polystyrene (the white stuff) Please bear with me. I am a painting contractor by trade, so I don't really know anything about this stuff. The questions I have are these. What mix should I use? What about adding lime, laytex of some sort, pool mix? My instinct is to tape the joints with mesh. Knock on a coat, scratch it up and let it firm up. Then come back with another coat and call it done. Will portland stick to styrofoam? Do I need glue? Will lime increase plasticity? What ratio do I use? Single or double hydrated? I want to mix my own because I'm just that kind of guy. Cheap. Does pool mix (marble dust) decrease the breathability of the stucco? What is the difference between marble dust and whiting? Any tips I should know? Thanks in advance.
Matt