Can Durock be used under ceramic tile?
nickjandrews
| Posted in Construction Techniques on
I am going to help my brother install ceramic tile in his house in Precott Valley, AZ to replace carpet. It has a crawlspace under it with wood subfloor. Can we use regular Durock under the floor tile instead of the more expensive Hardi-backer? And do we need to run thinset between the wood and Durock for bonding? Or would it be asking for trouble? Everywhere I’ve looked, it seems that there is a pretty big price difference.
Nick
Edited 6/21/2005 12:33 pm ET by nickandrews
Replies
Why are you going to put down durock? It doesn't add any strength, and you'll lose a 1/2" of height. Better to use 1/4" hardie or a membrane. If yoiur subfloor is not strong enough, you will need to install a layer of underlayment ply. Yes, I always use a thin layer of thinset between the hardie and the subfloor.
I'm sorry, I thought you wanted it done the right way.
Well, that's why I asked! I haven't done tile over a wood subfloor before and was wondering. Do we even need a backer layer if the subfloor is good? It doesn't give when you walk on it, and it is insulated underneath. The house is only about ten years old and seems pretty well-built. The guy working at Home Repot told my brother he had to use the Hardi-backer. As you know, that doesn't always turn out to be accurate...
Nick
Not a carpenter or tile setter,
I had GB in my bathroom, I had to tear it out and after some advice from the folks here I went with the Hardi, it may be a few bucks more, but the stuff if LIGHTER than Durock, and easier on the back. I had an old skilsaw and old carbide blade I used to make the cuts . Went thru the board like #### thru a goose ! you will only need the 1/4 backer board with Hardi as well instead of the much heavier 1/2 Durock just my thoughts maddog, (not Scott, ....... the other one)Edited 6/21/2005 3:26 pm ET by maddog
Edited 6/21/2005 3:49 pm ET by maddog
I used Durock before under tile for a store display of fireplaces and such, but not on a floor. Will have to check if the thickness is going to be an issue...
Nick
I just looked at the label on my stuff it reads, " embed the Hardibacker 500 in a 3/32 bed of mortar" Seems like more work? maddog..........,not scott........ ,the other one!
The hardie, and the durock, give you a very good tiling surface. Some folks will gasp with fear if you propose tile over plywood, but it's been done for many years and works well. The bigger question is if the subfloor is stiff enough. One layer of 3/4 ply is usually not enough, you need to try for more than an inch.
Any idea what you have for floor joists, what the span is, and the spacing?
I'm sorry, I thought you wanted it done the right way.
No, it's actually my brother's place. They did the insulation themselves, so maybe he knows. I'll ask him about. I'm sure he will be interested if he can save some moola. I am, of couse, concerned about grout or tile cracking, etc. I think he got the 16" tiles. What would you recommend as a maximum span and spacing for just wood subfloor? I guess we could drill through to gauge the thickness. If it's too thin, might as well go with one of the cement products vs more wood. The tile is going in the living room, kitchen, dining, hallway and bathroom.
If it were my house, I'd be installing a heat mat at least in the bathroom floor!
Nick
I'd be installing a heat mat at least in the bathroom floor
There's a past article on just that--worth searching for.
Also, know there's a thread or two on the topic, so, I'll do the "rezz" thing and suggest that you try out the "search" function for "tile floor underlay."Occupational hazard of my occupation not being around (sorry Bubba)
Yeah, I saw that in the magazine a while back. Thanks for the info!
Nick
Here is a deflection calculator to see if the floor is stiff enough.http://www.johnbridge.com/vbulletin/deflecto.plAlso lots of good stuff in their forums.
No, don't drill a hole in the floor. Almost a sure bet that it's 3/4 ply. The question is about the floor joists, which you would have to be in the basement to answer.
If it was me, and I didn't know/couldn't determine what the joist situation was, I would glue and screw a layer of 1/2" underlayment ply on top of the existing ply, then use a crack control membrane. 16" tiles ... are they natural stone (most prone to cracking) or ceramic or porcelain?
Someone suggested dens-shield. That's just sheetrock in a fancy wrapper ... that's not appropriate for flooring.
I'm sorry, I thought you wanted it done the right way.
Can you get Dens-shield, which is a gypsum product from Georgia Pacific, in your area? I think it's pretty good. Not too expensive, easy to cut and install.
Look here, see if you like it.
http://www.gp.com/build/product.aspx?pname=DensShield%c2%ae+Tile+Backer&pid=4684&hierarchy=pc
Ron
I just tore out a bathroom that was about 15 years old. There was floor tile thinset to the subfloor, and it came up incredibly easily. There was wall tile thinset to wonderboard and it was almost impossible to get loose, so I just tore the wonderboard off.
My advice is to use any of the cement backer boards that's 1/4" thick for your floor. And yes, set it in thinset. Use rock-on screws to attach it.
I prefer Durock in wet areas. And I get it in 1/4", 3' X 5' sheets and 4' X 8' (I wouldn't recommend the large sheets unless you've got help and a big layout to justify them).
I used GP's Denshield a couple of years ago....easy to use, but I wasn't impressed. It's moisture resistance is negligable.
Worm, I'm not totally sold on Denshield either..But do a search on it for failures. I can't find any. John Bridge's site doesn't query any info on Denshield failures. I've never heard any real people with real experience give real feedback on a Denshield failure. Have you tested it? I've used it. If done it to man./specs, I can't see a flaw in the stuff. And no, it's not just "sheetrock w/ a fancy wrapper". It's a proprietary fiberglass/gypsum composition INSIDE the fancy wrapper. It seems like a pretty good product for the right application (tub surrounds, not floors, methinks).. And I was damn impressed w/ the ease of use. C'mon--lugging, cutting and installing durock sucks, man.Higher-end installations, of course, I just use regular old sheetrock. And Kerdi. (Doesn't everybody?)
I know of no failures with Denshield, but this was what happened to me:
I was building a custom about 3 years ago and the HO found Denshield on the net and wanted it for ALL his tile substrate and for a room in the basement that housed a water pressure tank, a geothermal heat pump and a couple of water heaters.
His insistence on the product was its moisture/water resistance.
It was Winter here on the Oregon Coast and I hauled a full unit of the stuff from supplier to jobsite on one of my trailers. The unit was factory wrapped with plastic and we'd shrink-wrapped the load after it was strapped down.
In the end, there was a small tear in all those wrappings and the corner of about 6 sheets got wet. Those wet areas, about a 12" triangle, responded to the wet just overnite about like you'd expect of regular gyp board.
It didn't affect the project and we used the damaged sheets for cut-ups, BUT, I lost my faith in Denshield that day as "moisture resistant".....returned to Durock for the potentially wet areas.
And, I wasn't too fond of the little fiberglass hairs driving me nuts at days end....like putting in FG batt insulation.
Well, the product doesn't claim to be waterproof. But then, neither are CBU's. Difference is, Denshield may certainly be destroyed by moisture--IF it can penetrate and saturate. I did find it interesting that the manufacturer requires NO vapor barrier behind the panels. Leave the felt and poly off the walls in a Denshower. If moisture is allowed to be trapped in the core, it can fail. But how can this happen in a correct installation? Don't know. As of yet, know one has given me an example of how.But I'm with you on the little fiberglass hairs. They are a freakin nuisance.
Hey, I was just talking to a tile guy, asked him if he liked Kerdi...he said emphatically no, because he couldn't snap lines on it!
So, how do you do lay-out on Kerdi?
Didn't like Kerdi bcs he couldn't snap lines on it? Please.I've only used it for walls--I don't snap lines on tub surrounds..I use my stabila levels and either a pencil or a sharpie. Works for me. ANd honestly, I can't conceive of why a person couldn't snap a chalk line on it.
Just wondered....I haven't seen the product used, so just checking out opinions of peope who have....thanks
myself ... I prefer Durock.
3/4 ply isn't thick enough. And U can't "test" a floor by just walking on it. Drill that hole and see just how thick the single subfloor is.
backerboard isn't structural and doesn't qualify as "subfloor" ...
without seeing it ... sounds like U need at least another layer of 1/2 ply ... then the backer board.
thinset under the backer is needed. It's a leveling agent ... not an adhesive in this application. yes it does add a step.
backer seams need to be mesh taped.
nails or screws are fine.
Kerdi is a shower waterproofing ststem ... the name "Ditra" is what he's pretending to know about.
there ... I think I covered all the misInformation going on in this thread. That was exhausting ...
Jeff
Is the crawlspace dry?
Buck Construction
Artistry In Carpentry
Pittsburgh Pa
Edited 6/21/2005 11:34 pm ET by JEFF J. BUCK
There are several floor specs for tiling over 3/4" plywood subfloor in the TCA Handbook.
F144-05 is tile over thinset over CBU over thinset over subfloor over joists @ 16" OC.
F146-05 same as above but with 'coated glass mat water resistant gypsum backer board' (which I take to be Denshield) instead of the CBU.
Both methods specify joist deflection to max at 1/360. I think that's the most important factor, more than the ply. It's rare to see a house with 1-1/8 subfloor although I just tiled in one and it was like the deck of an aircraft carrier.
I've seen plenty of tile successfully installed over 3/4 ply. There is rarely a case when you can afford an extra 1/2" of ply plus the 1/4" of CBU plus the tile and thinset... buildup is over an inch. Yeah, you can do those little bevelled transition ramps up and down from the hardwood flooring. Hate those. I'd rather try to flush out with the hardwood.