Are you talking about a wet area? Or maybe the walls above the tile and above the showerhead? Technically, you could finish over CBU with USG Diamond Finish plaster–it would stick to the board and I’ve done a bit of that in bathrooms–but getting it to look good is not a job from someone who hasn’t done it before.
These defensive details give homes a better chances of surviving wildfires.
"I have learned so much thanks to the searchable articles on the FHB website. I can confidently say that I expect to be a life-long subscriber." - M.K.
Dig into cutting-edge approaches and decades of proven solutions with total access to our experts and tradespeople.
Start Free Trial NowGet instant access to the latest developments in green building, research, and reports from the field.
Start Free Trial Now
Replies
david, thanks for the reply. i have done plastering, on interior walls over blueboard. the area i'm speaking of is the complete walk- in shower walls. there are no tiles, except on the floor. i'm planning on tinting the plaster. would the diamond plaster be waterproof/ moldproof etc. or is there a better product or possibly an additive.
I don't see how you could put plaster as a wet surface in a shower, but hey, wadda I know? Sounds like you saw it somewhere. I seriously doubt a gypsum plaster like Diamond would be the ticket. Call USG tech support and see what they can say about it... they make a lot of plaster products... also have a good website.
Edited 4/2/2004 9:57 am ET by davidmeiland
Plaster is a mix of portland cement and aggregate. Swimming pools are "plastered," and Roman engineers lined the interior flow surfaces of their aqueducts with cement-based mixes. Stucco is "plaster," and the villa we stayed in in Mexico, recently, had all the glamour baths done with stucco-walled showers.
Waterproof? No problemo.
I've asked about this in probably 5 different ways, be/c I have a big need for this kind of thing, and the answer always comes back that stucco is not waterproof, won't pass code, is subject to cracking, can collect bacteria, and so on.
Any idea on how to resolve the gap be/t what you've seen and what others here have said? I believe each of you, but the viewpoints aren't compatible and I can't resolve the gap.
Find a contractor that does concrete swimming pools. Ask him what is used when they gun the sides and bottoms.
The ingredients, for the most part, may be the same...but the proportions differ.
Pools guys here once told me the ratio they shoot for the pool shell. Something like a 5:1 ratio of sand:portland. The sand/portland comes out of one nozzle as a dry mix and on its way to the wall, it mixes with water shot from another nozzle.
A marbelite or marcite pool plaster finish would have a different ratio, as well as other lesser additives.
The more fines you have in a portland-based mix (with portland being "finer" than sand) the more resistant the mix is to water penetration.
Good points from all.
So, I wonder what the Mexicans are using down in Puerto Vallarta, where I saw all this stucco in showers?
Actually, "showers" in Mexican bathrooms often consist of a shower head and controls sticking out of the wall, and there may or not be any wall baffles to separate the shower from the rest of the room. There is a floor drain, but often not a curb.
The floor gets wet. The walls get wet. Where we stayed, the floors were all concrete, with a lot of decoration in exposed aggregate, some of it being silver-dollar-sized smooth pebbles done in fabulous decorative patterns.
But the walls were all stucco over CMU, just troweled on, probably a base coat and a color coat, no diamond lath. In some areas ceramic tile was a finish, but I saw a lot of just plain old stucco in the path of the shower spray.
>Find a contractor that does concrete swimming pools. Ask him what is used when they gun the sides and bottoms.
I know about gunnite be/c that's how we build the houses I design. As some pointed out to me when I last asked about using swimming pool plaster in this application, the water has chemicals in it to prevent the growth of bacteria. That wouldn't happen inside.
I still face the issue of what will get code approval...
I talked to these folks at the FHB Builders Expo in Worcester MA a couple of months ago:
http://www.protexcote.com
It's a two-part polyurea spray system. They seem to claim it can coat almost anything.
Al Mollitor, Sharon MA
You've all but disappeared from this forum. What happened?
Very observant, David. Combination of things. One, I've been working a bit more and screwing around a bit less. Two, I tend to feed one addiction at a time. Now that rumors of Spring are getting more persistent, I've been getting out on the bicycle and surfing bike stuff on the web. Three, there are so many smart and experienced folks on this forum, it usually seems that anything I might offer has been pretty well covered. I still check in, but mostly to read and learn..and get a dose of some of my favorite characters on here.
Al Mollitor, Sharon MA
A friend sprays polyurea, and it's awesome stuff. But I'd still love the feel of the concrete/plaster, since that's what the rest of the house is. If a free-form plaster-based system was figured out that passed code, probably half my clients would be including it. Just perfectly fits the structure. The polyurea is too slick and rubbery...gotta add grit for the floors.
Cloud, here is a link that I ran across that might help. I have not used this so I can not say how well it works. It is a little exspensive..
http://www.artisanfinishes.com/techinfo.htmlWe are the people our parents warned us about. J. Buffett
I was referring to Diamond finish plaster, which I had put up by the square mile on walls and ceilings. I don't think you could put it on a wet wall, but I'm ready to be straightened up if I'm wrong.
I have a feeling you may need to do a conventional-plaster-with-lath covering, not just a two or three coat veneer. The kind where the scratch, brown, and finish comes in at about 7/8" total thickness, and the scratch is bedded into the lath.
Jake, I'm going to go out on a limb here and think out loud with you a little, since it really is an interesting challenge.
Gypsum plaster is out of the question. There is a plaster called Keene Cement that you could use in relatively humid areas, but I don't think water contact is a good idea for this stuff, either.
If you were to pay attention to the waterproofing on the walls, especially where the walls meet the pan, I bet you could make a Portland cement plaster work. No matter what you do, you need to waterproof the wall behind the stucco. Let's assume you have a stud wall. If it were my house, I would sheathe it with 5/8 CDX, and cover it carefully with bituthane, like maybe Mira-Dri. I might even use a couple of layers. (You mentioned a cement backer board – I suppose this could work, but you would still have to waterproof behind it very carefully.)
Then some expanded metal lathe, applied with galvanized nails, properly oriented and lapped. If you want it to be really flat, consider low-rib lathe.
I'd definitely do a three-coat job. Mixing stucco is as much an art as a science, and conditions always vary. The first (scratch) coat I'd want to be really strong, I'd probably go with about 18 to 20 #2 round shovels (maybe 4 or 5 cubic feet) of clean ASTM plaster sand (clean sand and clean water is crucial) to a sack of cement. No lime, no plasticizer, no masonry cement. Minimal amount of water to get a workable mix, and I would definitely use Anti-Hydro. I don't know what the stuff is made of, it's been a secret for years I suppose, but it makes anything with Portland cement work better. Lay the scratch coat on about 3/8” thick, rake it lightly when almost hard. Let it set two days.
As for the brown coat, I think Mongo is on the right track. If you were to use an ASTM plaster sand and add several different grades of some finer sand, like maybe the variety of silica you can get at good hardware stores, it should get really tight. If you use a little more sand in the brown coat, you should end up with a really strong second coat that does not crack. I would add some acrylic fortifier (watch out for the false set, don’t be tricked into adding too much water). I’ve had real good results with this stuff. Use a commercial quality product, follow the instructions, and you get a very strong material. If it does crack, no big deal. Apply some nylon mesh and bonding adhesive, and try again.
Wet the scratch coat down thoroughly before applying the brown coat. This will help control the capillary “suction” and help reduce cracking by helping with an even cure rate and adequate moisture for full hydration. Trowel the brown coat on 3/8” thick, float it out when it stiffens up, and hard-trowel it smooth when it just takes a thumb-print. Wait three days. It should be looking pretty hard and tight.
Again, if it were my house, I might roll on a bit of bonding adhesive (commercial stuff like Hornweld or ElRey100, no HomerDesperate Quickcrete Brand Elmer’s Glue) before I put the color coat on.
As you can tell, I can’t see a reason in the world why you couldn’t do this with good result. If you do end up with a less than satisfactory result, you can always tile over it.
Please do let us know how it turns out.
DRC
OK... we got someone who knows their stuff here... time for the rest of us to stop guessing.
Thanks for the vote of confidence.
Sure, I've spent a little time with a trowel and a whole lot more time trying to not get screwed by stucco subs -- but I have never built a shower this way. Pure speculation informed only by the experience that I've had at other applications.
Be all that as it may, now I'm tempted to try this, too. It sounds like a pretty cool idea. Just think, a shower that is any shape you want, no corners, and a comfortable seat? Wouldn't be too hard to design so it had no door, either. Maybe even no curb and easy access for old people or folks in wheelchairs. Might even be easy to clean -- what if a person was to use a masonry sealer (like maybe OKON) on the stucco so the water would run off a little faster?
OK, I'm on a roll now. How about we run a radiant heat tube through the whole thing?
DRC
I was once told plaster and stucco are the same thing. It's just called plaster if it's applied inside, and stucco if it's for exterior use. That's from the mouth of a guy who's been troweling since before I was born.
Plaster binders are usually something along the lines of gypsum, lime, and portland cement. Different binders impart different qualties to the plaster.
Gypsum plaster should not be exposed to water, which limits it to interior and non-wet locations, I think Dave already wrote that in his earlier post. Gypsum rock is crushed and then heated. The heating, or calcining rids the rock of the majority of it's held water. This calcined rock is then ground up to a powder. Keene's cement is still a gypsum-derived plaster. To make Keene's, the gypsum is heated until just about all of the held water is driven off. Keene’s cement can give a very hard and fine textured surface when troweled.
Lime and portland cement plaster maybe used both inside and outside, or dry and wet locations. The most common aggregates are sand, perlite, and vermiculite.
What ever happened to the plaster guy that used to hang out here maybe four years ago or so. Brian? I think he had a site, or hung at a site, called http://www.ornamentalplaster.com or somethng like that.
Mongo , I think that Brian got fed up with some one jumping on his chit . Seems that every time he posted a response some one would claim that he did not know what he was talking about. And if I remember right he was a long time plasterer. One of his last post was about ceiling medallions and how he installed / made them.
Too bad. I remember his posts as being helpful.
It is one of the downfalls of these forums, I suppose.
thanks dave and all,
i've since been looking into two products. are you familiar with thoroseals plastermix , or conproco's conpro-plaster mix? each is designed to withstand loads of hydrostaitc pressure, used for below grade coatings, water tanks etc.
i can't see why these wouldn't do the job for shower walls? if you can let me know please.
check them out at http://www.chargar.com or the sites for thoroseal or conproco.
also a great article in FH # 127 with a shower similar to the one i'm designing. nice job and pics, unfortunately no info on the plaster material.
You're on the right track.
Here's another link: http://www.lahabrastucco.com/C2210_shower_fin.htm
Remember, take Dave's advice regarding good base/scratch coats. Since this is a shower, you need the plaster in a good plastic state for workability so when you trowel and work the mix you get a nice, tight, "no pore" finish.
Definitely snap some progress pics for an eventual "how to" thread.
Thanks for the link. First one I saw that directly mentions showers. Now if I can just wok out the concrete floor detail...
Very likley a naive question, but I'd think it'd be easier and safer (leak-wise) to have a monolithic, or integral, shower in an all-crete dome, as movement-wise, the structure would be more stable than a wood-framed house.
In domes, are interior partition walls generally wood or steel stud framed?
How about floor platofrms? Are they poured as well, or post-framed with wood or engineered lumber?
I agree on the stability of the structure and the similar expansion/contraction. Walls can be done any way, as can floors, but I'd specify a shotcrete wall for this area for this purpose. The challenge is the slab floor and the wall/floor intersection. Slabs can crack and need sealing. Installing a drain that won't let water where it doesn't belong is a trick, be/c the 2-part clamping drains won't work the same way as normal. And getting an acceptable wall-to-floor detail is important--don't want water rolling down the wall to get trapped under that joint or just soak into the slab or beneath the slab.
I can see a building dept accepting the product you linked--thanks again for that!--but I gotta flesh out the rest of the details, too.
Why can't you do the floor same as regular shower? Preslope , membrane shower pan drainclamp ring, then your mudbed(in your case finnished floor) . Then use a flex caulk to seal the wall to floor.
>then your mudbed(in your case finnished floor)
The mudbed as a finished floor?
Yeah ,the mud bed would be concrete. And there would not be any issue with water seep as it would be over a waterproof membrane that slopes direct to the drain.
You would have to do a good finish on the mud bed . Maybe trowel in some color or acid etch or both.
Never thought of the mudbed as a finished surface. Anyone else have a thought on that? Any potential problems to note? And someone mentioned a sloped slab, membrane, and 3" of concrete over that. Is that worse or better than the mudbed as a finished surface?
Edit: Boris has been generous with his time answering my questions on this kinda application...I wonder at his thoughts on the wall material Mongo linked and on Don's floor idea...
Edited 4/5/2004 9:57 am ET by Cloud Hidden
Thanks for that link, Mongo. I could be dangerous with that stuff. <G>
DRC
So Dave, with your background, and assuming you have issue 127 p 48, how would you guess those walls were done and integrated with the floor?
As was mentioned, I'd LOVE to see something like this documented w/ photos during construction, 'cause I could use it over and over and over.
I'll have to go dig out #127 and get back to you.
DRC
The picture on page 48 of that issue is exactly the kind of thing I've been aiming for. Wish they did a wall detail. Would love to see their material layering. Same with the floor--it's a slab, which several people here have said should not be a shower floor. Yet they found a way to--I assume--get it done. Wish the author was here to quiz...
A little (lot) off the subject of plaster showers, but....... I spoke with the people who do spray on truck bed liners a while back and since they guarantee the product on trucks to be waterPROOF forever, as well as to standup to the abrasion problems, they could see no reason why their product would not work as a complete shower surround.
With this idea you could form any shape shower enclosure, even with paper mache, and have it totally waterproof. Textured, too.
yeah isn't that a beauty. wish i could talk to the dude. .
i don't see why everybody is worried about the slab floor. i did a pre-pour, a membrane, and 3 inches on top of that, plus i'm tiling the floor. i'm thinking of doubling up the cbu and an additional vapor barrier on the walls, before i plaster.
what do you think of sealing the first joint of cbu between wall and floor with a polyurethane caulk, maybe set the second layer of cbu right on another bead, then plastering right down to the tile?
I did this to the shower in one of my rentals many years ago. I was trying to find a way to make the showers more durable since the tenants were tearing up the fiberglass surrounds I had been using. It is a corner shower with one wall being block and the other cement board. It's been probably 12 or 13 years now and I've never had a problem with it. Finished it off with 2 coats of pool paint.
plastering shower
My life is my passion!
http://CLIFFORDRENOVATIONS.COM
Sorry, didn't read every response. The answer is Tadelakt or Italian plaster modified for showers. I've done several prepping them just as you would for tile but skim the entire membrane surface smooth like stucco with thinset, then add 2-3 layers of plaster and seal with 511 impregnator tile grout sealer.
You're 15 years too late.