We have a gypcrete pour over pex and we want to lay tile on top of it. We know that thinset to gypcrete directly is a bad idea, and are looking for the best solution.
Has anyone used a product like Red Gaurd over the gypcrete then thinset then tile? How did it work for you, and how did you lay down the Red Guard?
I’ve seen ditra used, but we are concerned that using a membrane may reduce the thermal flow, and/or may lower the structural stablility. Any thoughts?
Many thanks for any idea, it is the first time we are using this combination, and we want to get it right from the beginning!
Amy
Replies
I'm not convinced that thinset directly on gypcrete is a bad idea. At least I hope it's not since I did my own bathroom like that. (Two years old and still looks like new.) Some say that the gyp should be primed first. There's some info on the john bridge forum about that although most of the pros there have a great disdain for gypcrete altogether. My gypcrete contractor said to simply use a thinned latex paint primer to seal which is what I'll do in my second bathroom. I'm also planning to use redgard in there as a waterproof membrane.
I wouldn't think that the ditra membrane would act as too much of a insulator. I've got 3/4 inch oak over most of my house (over radiant embeded in gypcrete) and it's OK. All layers will increase the response time, but will still allow the heat to get into the room eventually. Also, isn't ditra adhered with thinset?
You should be able to get some documentation from your installers regarding the compatibility of the underlayment, PEX, and the installation of tile or stone as a finish. Refer to the underlayment manufacturer's instructions. Most will require a latex sealer (not paint) and some may require a waterproof membrane if used in a wet area. Also, read the instructions and limitations on the bag of thinset.
Red Guard, IMO, is absolute garbage. You can find much better WP products out there.
-Bill
>>> Red Guard, IMO, is absolute garbage.
Can you please elaborate on why you think so? I have no experience with this stuff, have come close to using it once (I bought then returned the container) and found out something that changed my mind (I'll share this in a later post).
Thanks
I was given a lot of free product when a distributer started to carry it. My experience is that it is harder to work with, and does not perform as well as other similiar products. In my own home I used Hydraflex by TEC, a superior product to Laticrete 9235. Nobleseal is very good, and for iso membrane, ECB is the best. IMO.
Colvin - Crack iso membrane may or may not be required. In order to not have any warranties voided, you must find out what the u/l manufacturer requires for installation of tile or stone. Maxxon requires a primer/bond coat, and USG requires waterproofing subgrade. Find out what is needed, then find the installation product that is compatibile with gypsum floors.
We've put slate over gypecrete and hydronic heat with mixed results if done sloppily and good results if attention is paid to tile adhesion.
The problem with gypecrete is it's lower surface strength so less than full thinset coverage results in tiles that are more likely to pop. It's also very important to use a scratch coat. I really like the idea of priming the area with a bonding agent to help solidify the top layer, although it may not do any more than a good scratch coat and 100% coverage with a good quality thinset would.
Beer was created so carpenters wouldn't rule the world.
Gypcrete is very common in these parts. I have seen hundreds of pours. I have never seen ditra used over gypcrete. I have seen Ditra over concrete but not gyp. It may be a regional thing. Most tile setters here use a product called "Blue Devil" It comes in five gallon buckets and is rolled on. It makes a rubbery hard membrane that adheres extremely well to thinset. A bucket costs about a hundred dollars and covers about 500 SQ FT.
Thanks everyone for your responses. It is great to hear from folks who have seen this stuff and work with it. I had read the John Bridge forums, and indeed it seems like they are down on gypcrete, and that it may be a regional thing.
So it sounds like a primer/sealer is the way to go.
Mike, I did a search for "blue devil" on the web but couldn't find anything that looks right. Can you tell me the manufacturer, and where you generally purchase it?
Has anyone worked with Ardex P51? That is what our supplier said to use, but overall we were not impressed with thier pour and question their recommendations because of it.
Use a good crack isolation membrane, and you're good to go.
Laticrete has one, I think, I don't remember right now which one I use.
_______________________________________________________________
I'm off to see the wizard...
Laticrete 9235?
.... or Blue 92?
Amy,
Absolutely use an anti-fracture membrane (AFM), something like this: http://www.nacproducts.com/ECB.htm It will not affect the heat. It will keep you from worrying about adhesion between the gyp and the thinset. Just be careful rolling it out. If you get the adhesive side stuck to itself, it won't let go and you'll have a ridge that's a pain to deal with. You can't easily pull it out, because the material is elastomeric and will stretch. But the surface is textured for a great bond with the thinset. Haven't had a single problem with adhesion. In fact, a worker dropped a hammer and broke a tile. Getting the pieces and thinset off the membrane was much much harder than getting one off concrete. Don't take a chance. Use an AFM.
Ok, I'm just starting out here, so bear with the questions. =)
Is it fair to say that the primary function of the AFM, whether it is Laticrete, Ditra, Nacproducts ECB, is to enhance adhesion between the substrate and the thinset?
If this is the case, would you argue that and AFM should be used ANY time a large (or even small) installation goes down regardless of substrate?
OR... is the AFM suggested specifically in the case of gypcrete pour on hydronic floor?
An anti-fracture membrane is there to prevent cracks in a substrate from telegraphing thru the tile. It is common to use a membrane over concrete slabs so that if the slab develops cracks you may not get a corresponding crack thru the tile.
In my opinion you need a prescription for this job provided by the manufacturers of the materials. I would talk directly to the gypcrete supplier and find out what he knows. Perhaps there is a trade org for gypcrete that publishes application specs. I would definitely talk directly to Laticrete, Mapei, or Custom Building Products and find out what they have to say regarding applying their membrane and/or thinset materials over gypcrete.
What meiland says goes for me, too. It's to not telegraph cracks to the tile. Thinset can bond so thoroughly that it'd crack the tile before giving up its bond. I used the AFM recommended and sold by my gypcrete installer. Doing that gives you someone to speak with if you encounter problems. Otherwise, you might see finger-pointing--"it's THEIR fault!"
I just remembered that I have the Tile Council handbook sitting on my shelf.
Their method RH111-05 is for "poured gypsum underlayment, hydronic system, thinset". What it shows, bottom up, is concrete slab, primer/sealer, tubing embedded in gyp, primer/sealer, CI/waterproofing membrane, thinset, then tile.
Method RH122-05 is similar except that joists and subfloor are shown instead of concrete.
For both methods the diagrams indicate crack isolation and/or waterproofing and/or uncoupling membranes. Maybe any will do...?
The membranes, mortar, grout, etc., are related to various ANSI specs and such. There is a note stating essentially that some membranes are to be used with primer/sealer, and that manufacturer's instructions are to be followed.
So, just like everyone here has been talking about...
Ok, sounds like doing some phone research may be the best bet from here on out... Call the gyp company, see what their opinion/recommendation is and go from there, following manufacturers instructions as we go.
The argument seems to be leaning strongly towards primer then membrane... anyone out there just dying to vote for primer only?
Are most of these products available at places like Home Depot, or will I most likely be ordering through the manufacturer?
I think I'm making this harder than it is. And sapwood's inital response makes me smile now... his way was super simple and it seems to have worked.
Again, thanks to all for your input.
I would call probably Laticrete and see what they say about your application. They make membrane and thinset, so that covers both areas. It might be worthwhile finding out which manufacturers' products are easily available in your area, then going that route. Anyway, I don't shop at Home Depot much and I doubt they have this kind of stuff.
Also, I would not skimp on a tile installation. When they are not done correctly and go bad, they are usually torn out completely, or sometimes left to fail a little at a time for eternity.
So... find manufacturer--->call them--->follow their specs--->enjoy floor. Hopefully!
Ooops. I now remember that I first layed a layer of 1/4" wonderboard over the gypcrete befor tiling. The wonderboard was to bring the grade up level with an adjoining floor. It was thinset to the gyp, then the tile was thinset. I'm going to use a roll-on or trowel on membrane in my next bathroom to guard against any water reaching the gyp or subfloor. In winter any water should dry out of the floor, but in the summer the heat never comes on. And just to reassure everyone, I shower throughout the year.I've read on the John Bridge forum that redgard is commenly used and well thought of. I'd like to know of any problems with it.
Thanks Cloud for that membrane site. That looks like a fantastic product for our current project.
How much per sq ft is this product?
blueOur Skytrak is for sale. It has 500 hrs on it. We want 50k (you pay the freight) and we'll finance it. Drop me an email; it's a good buy.
Google "anti fracture membrane" and you'll see a bunch of options. I just picked one, be/c I didn't remember the precise brand I used. This looked similar/identical. I used it in probably 2000 and it was something like $300 for a 3' x 100' roll, though I may be off by a factor of 2. It was whatever AFM my gypcrete contractor supplied. 2000 is ancient history when it comes to remembering costs and sizes.
Thanks for that info Cloud. The stuff was $1 per sq ft in 2000 and even if it's tripled in price, I'm estatic.
blueOur Skytrak is sold. Frank sold it for 47k cash.
I would think that something like Ditra would help when it came to replacing the tile (if that may be your concern someday).
Scott.
Always remember those first immortal words that Adam said to Eve, “You’d better stand back, I don’t know how big this thing’s going to get.”
I'd membrane the gyp. Ditra, Nobelseal, PVC, something. Not a big deal.Regards, Scooter"I may be drunk, but you're crazy, and I'll be sober tomorrow." WC Fields, "Its a Gift" 1934
I have put porcelin tiles directly on a hydronic floor system using a gypcrete pour.
Nothing has moved and I placed this on a 1.5" styrofoam base. Today, I would use a anti-fracture membrane like Ditra before any stone type tile. Be sure to use a "dry-setting" thinset which in Toronto, Canada only costs less than $9.00 vs. $17.00 for latex modified thinset. Be sure to use a dry set mortar to lay the stone tiles. Absorbtion does not seem to be affected by the stone for cupping effects.
Ditra does not affect the mix temperature for the tiling. Used under electric radiant heating really!
When in doubt, membrane it. Ditra, PVC, Nobelseal.Regards, Scooter"I may be drunk, but you're crazy, and I'll be sober tomorrow." WC Fields, "Its a Gift" 1934
As much as I hate to admit it, one of the decoupling membranes is what I'd use on a client's house since they are readily available and reasonably priced.
Beer was created so carpenters wouldn't rule the world.