Tile on top of Thermofin

Andrew_7

Regarding a stable tile installation, what do I need to put on top of the thermofin U/plywood sleeper sandwich to provide a stable uncoupling layer for small ceramic tiles? I don't want the floor to start cracking next winter. I will be able to get enough heat out of the floor, I just don't want to raise the height too much above the adjoining hardwood.

Andrew

Andrew_7

Regarding a stable tile installation, what do I need to put on top of the thermofin U/plywood sleeper sandwich to provide a stable uncoupling layer for small ceramic tiles? I don't want the floor to start cracking next winter. I will be able to get enough heat out of the floor, I just don't want to raise the height too much above the adjoining hardwood.

Andrew

Andrew_7

Regarding a stable tile installation, what do I need to put on top of the thermofin U/plywood sleeper sandwich to provide a stable uncoupling layer for small ceramic tiles? I don't want the floor to start cracking next winter. I will be able to get enough heat out of the floor, I just don't want to raise the height too much above the adjoining hardwood.

Andrew

Mike T., Swampeast MO

Cement board is awfully hard to beat for any ceramic tile installation. IMHO it's a true "wonder product" of the last few decades that's quite comparable to MUCH more expensive and FAR heavier mud jobs.

If the ½" thickness is too much, I suppose you can use "Wonder Under" (or similar). It's much newer than cement board and may or may not prove to be as good, but I think it comes as thin as ¼"--certainly 3/8".

Dale Pickard

We use and recommend Dens Shield from Georgia Pacific. It comes in 1/4", 1/2" and 5/8" and 4' x 8' sheets. I would set the Tile backer in thinset mortar and fill the open grooves with thinset, especially if using the thin stuff. I much prefer Dens Shield to cement board, like Durock. Dens Shield is flat, comes in large sheets and scores and breaks like sheet rock.

See,
http://www.gp.com/build/product.aspx?pname=DensShield®+Tile+Backer&pid=1511&hierarchy=pc

Dale Pickard
Radiant Engineering Inc.
Bozeman MT

Dens-Shield® Is The Ideal Substrate For Wet and High Humidity Areas

Atlanta, GA. May 17, 2000 -- When protection from moisture intrusion is required on interior walls and ceilings of swimming pools and natatoriums, Dens-Shield® Tile Backer is an ideal selection for use as a substrate. Since its introduction in 1987 by Georgia-Pacific, Dens-Shield has performed as a superior substrate for interior tile installations. The same properties, which make it an outstanding tile substrate, are equally appropriate for non-tile areas, which are subject to high levels of humidity and moisture. Dens-Shield is engineered to protect the integrity of an application while providing an excellent surface for smooth or textured finishes.
Dens-Shield protects any wet and high humidity area with its unique acrylic coating which acts as a built-in surface moisture barrier. Dens-Shield has proprietary fire and moisture resistant qualities, which make it the preferred product to be specified for walls and ceilings in enclosed swimming pools, laboratories, natatoriums, and other interior areas subject to high moisture.
Its acrylic surface coating keeps moisture from migrating where damage can result and protects the integrity of an installation. The additional benefit for non-tile applications is that a variety of finish coatings can be used which are available from several manufacturers.
In addition to providing superior moisture protection for interior surfaces, Dens-Shield is lighter than cement board and has many labor saving features, which make it faster and easier to install. Dens-Shield is available in a wide variety of sizes. The 1/2" variety is available in 32"x 5', 4'x5', and 4'x8'. There is also a 5/8", 4'x8' panel that is the only Type-X fire rated wet-dry application substrate for commercial systems. The 5/8" Dens-Shield panel aligns perfectly in applications where other 5/8" substrates used.
Dens-Shield meets ASTM C-1178 as a glass mat gypsum substrate for use as tile backer, Dens-Shield complies with the following codes: BOCA #90-30; ICBO #4465; SBCCI PST & ESI #9567-A; Los Angeles RR 24917; New York City MEA; 65-88-M and Wisconsin DIHL 910014-S.
Georgia-Pacific, one of the largest building product manufacturers in North America backs Dens-Shield with a limited 20-year warranty.
To learn more about how Dens-Shield can be used for finished non-tile surfaces in high humidity areas, please call our toll-free hotline on 1-800-225-6119 (Monday through Friday, 8:00 AM to 6:00 PM EST). Call 1-800-BUILD-GP (1-800-284-5347) or visit www.gp.com on the Internet for product literature and general information about Dens Shield and other Georgia-Pacific products.

Mike T., Swampeast MO

Heat Transfer Question

How does the lower mass of the shield tend to diffuse the heat compared to cement board? Is any change related to the slightly increased resistance of the shield?

p.s. I still look up "resistance" in the Sepller Syllabifilicator on top of my monitor.

Drew_2

Stable Tile

Go to www.noblecompany.com , click on products, click on CIS membrane. This may be what your looking for. The thickness is about the same as two business cards and has a R factor of less than 1.

Andrew_7

I had thought about using this (I already found the local distributor), but I'm a little concerned about where it would bridge over the tubing. I can fill that area in with self leveling concrete, but what about the motion of the plates as they expand and contract? I'm not very concerned about R-values, since the tubing is close to the surface and the joist space is insulated below, just about using the Thermofin in a method that sufficently supports the tile.

Mike T., Swampeast MO

I've always installed cement board with mortar just as Dale mentioned with the Dens Shield. Have always used a 1/4" x 3/8" notchet trowel for applying the backer. I then fasten the backer to the substrate. For floors I usually attach with electro-galvanized roofing nails, for walls/other with the rather expensive dual-helix "cement board" screws.

I like the cement board that has a semicircle of "extra" fiberglass netting extending from the long edges. You just butt these edges and force in mortar. For cut edges it's best to apply a bit of thinset to one, put the other against this mortared edge then finish the joint in "drywall fashion" with fiberglass tape and mortar. I was taught and have read that cement board should be installed like common bond brickwork. I've made a number of washing machine "overflow pans" in this way (no membrane like a shower) and they are waterproof. After five years one of these averted an absolute disaster (drain hose came out of fitting somehow) with only very minor damage to surrounding walls from the spraying. In another a slow leak had been occuring for many months before owner bothered to repair the problem--again no water penetration.

The Dens Shield is likely similar, but most certainly read and follow the installation instructions.

Make certain you use a polymer modified thinset--most particularly for attaching the backer to the substrate. Many thinsets have the polymers incorported into the mix--with others you use a proportion of "add-mix" instead of water. The polymer modification helps it join dissimilar materials (like wood and cement) and gives the ordinarily brittle thinset some flexibility. As the name implies, thinset is intended to be used quite thin--but the slight irregularity from the D-fin shouldn't be any problem--that's why Dale recommended filling this area with the thinset.

As long as floor deflection is within limits (usually 1/360th of the span) I seriously doubt that you'll have any problem with cracking that telegraphs through the backer board to the tile.

Isolation membranes are available from good supply houses, but they can be expensive and tricky to apply. {Tar paper is sometimes used, but I wouldn't suggest it in a radiant panel application.} I very seriously doubt that Dale would have suggested the Dens Shield product applied with mortar if he expeced ANY sort of problem.

Dale didn't say, but I would assume that any fasteners used to attach the backer to the floor should be into the floor itself--not through the plates.

hr

Swampy hit the nail on the head

undersized or over spaned joist are what leads to tile or grout line cracking in this application. If the floor is good and solid, the method Dale has indicated has always worked for me.

Stand mid joist span in that room and jump up and down. You'll know if the floor assembly is up to the task

hot rod

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Andrew_7

Well, I do know that the joists are up to snuff. They passed John Bridges deflectometer. Then, for good measure, I sistered most of the joists so that I would have a flat surface, then added blocking for a little more stiffness, and have now added sleepers and plywood infill to provide a level surface for the Thermofin. One joist was originally doubled up, so that one is now five pieces of lumber wide. I was just concerned since the plywood between the tubes is not continuous, like a typical subfloor underneath cement board.

Question for Dale, though. I was planning on 6" spacing of the tubing in the Thermofin, to ensure that I get enough heat out. This, then, would require nailing through the plates. Is there any problem with this? The cement board, though, would only be nailed into the top plywood layer. And for the half-circle loops at the end of each run, would self-leveling concrete work as well as the product suggested on your website? I have to bridge one area anyway, so will probably be mixing some up.

Andrew

Mike T., Swampeast MO

Check the instructions...

...on leveling compound bags VERY carefully. Many expressly say "not for use under cementious underlayment or ceramic tile".

If the cracks are no more than ¼" wide or so, I don't think there will be any problem filling them with thinset. For wider you might want to make a rich, dry mortar mix (1 part Portland, 3 parts sand, VERY little water) for filling.

hr

There are a bunch of tile websites

both manufactures and associations that have good help and advice for various installation methods. I'll bet they could help steer you to the correct products, also.

Try a web search for tile associations

www.tileusa.com

www.ardex.comwww.

www.floridatile.com

hot rod

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Andrew_7

I looked at the specs on the web for Mapei, and they didn't say anything regarding being under cement board, and at a bag of Novoplan 2 (sp?) at Lowe's last night, and it also didn't say anything about cement board.

I will probably need some SLC or mortar anyway, because there is an alcove off the end of the bath, and the threshold between the main part of the bath and the alcove needs to be filled in level with the joists. It is currently some brick and steel plate and random bits of lumber. Mortar might be best for that, as some areas are deeper than 1/2". But other areas, including the transistion into the hall and the bends in the heating tubing, will require something like SLC.

hr

Levelers and adhesives

are not the same product. You may need one product to level those areas, and another to adhere the CBS to the floor and level compound. BUT you want to make sure the two work together!

I'd still call the manufacture of the product you looked at to get an OK. Hate to see you do it twice

Feb. 04 issue of jls had an article on polymer level compounds, and topping coatings. They can be applied to 1/16" thickness, set to 3,000 psi in a few hours and 6000 psi in 24 hours. Very flexible.

Try www.jlconline.com Some articles are free, other downloads they charge for.

Polymer manufactures include www.concretesolutions.com www.designerfloors.com www.colormakerfloors.com

Some of these polymers are being colored and used as a final floor covering. The article shows some 1/2" overlays that have been acid stained and cut into a grid to resemble a tile finish.

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Andrew_7

Calling is a good idea. If I use SLC, I will get both it and the thinset from the same manufacturer, and if the labels don't explicitly state that they can be used together, I will call to find out. I'd go with a premixed
version, to limit the range of mistakes that I might make. Don't want to do the job more often than necessary. :-)

I read the article you posted. Interesting stuff. If we ever finish the basement, I might try something like that.

Andrew