I am about to begin tiling the back hall of my home, a primary entry point from the garage. The tile will extend into the 1/2 bath (I will remove the existing tile) and a small laundry room (will remove sheet vinyl flooring).
I will most likely use a ceramic tile, as opposed to a natural stone (slate, etc..). After reading a recent FHB article on Ditra it seems like the way to go. Using Ditra will allow me to eliminate the use of backer board, and will allow the finished floor height to better match up with the hardwood in my kitchen and study.
The house is 8 years old, and has 5/8″ plywood sub floor over 16″ oc floor joists (2×10’s, max 10 foot span). Does anyone have experience with Ditra that would suggest I should not use it in this install?
Many thanks in advance for your expertise.
Replies
I'll let the tile experts here weigh in but my guess is that the 5/8" subfloor, Ditra or no Ditra, is insufficient. I myself would be wary.
Jon Blakemore
RappahannockINC.com Fredericksburg, VA
All,
thanks for the words of caution. I'll have to go home and pull a floor vent cover to measure the thickness of the sub-floor. It may be 3/4", at which point I assume deflection will not be an issue. The hallway, bathroom, laundry room is fairly narrow. From the garage entry to the outside wall of the laundry room is about 12 feet, and is supported by poured concrete foundation under the garage and outside laundry room wall (length). Going the other way (width?) I have a finisehd basement wall under the bathroom wall providing additional support.
So, all in all I have good structural support from underneath, I just have to check for the thickness of the sub-floor.
And based on reading the archives it seems like Ditra is a reasonable choice, if not a bit more pricey. I live near Philly so do not expect availability to be an issue.
Also, this is my first tile job and Ditra seemed a bit more user friendly. I have installed over 600sf of t&g hardwood strip flooring recently, so can follow directions pretty well.
Many Thanks.
I don't remember if they mentioned it in the article in FHB but make sure the thin set that you put between the subfloor and Ditra is on the wet side and make sure you have good contact between the cloth side of the Ditra and thin set. Good luck!
Ditra itself is a great product, but Jon is probably very correct to be wary. You need to first resolve the deflection and make sure that what you have is either sufficient or make the floor so it is. While that might involve more thickness to the floor, one thing the Ditra will help you avoid is even more height. You can assume that mud under and mud over it, you've only added maybe 1/4" before you're to the bottom of your tile.
"A bore is a man who, when you ask him how he is, tells you." -Bert Taylor
There's absolutely no way that Ditra or any other thin membrane can make it possible to ignore the problem of deflection. Tile can't bend, period. Consider dropping the subfloor on cleats between the joists to get more depth.
-- J.S.
I used it for the first time in my own house. In the second floor bathroom we have 2x12s 16 IOC with 3/4" ply subfloor with a span of 16 feet. There is enough deflect that some of the grout has cracked and some times are now loose. The wisdom back then was that 16 foot spans would be OK.
However, we are extremely happy with the performance in our 36'x20' family room. The difference there is that there are three spans of 12 feet each for the 2x12s (for a total of 36'). After 3 years there are no cracks anywhere in the fam room.
Soooo, be conservative regarding deflection...
Amanna: Go to Schluter's site http://www.schluter.com/
and read the technical info about Ditra. Then read the related info from the Tile Council of America's handbook.. All your questions will be answered.
Cliffnotes version: if you have 2x10's on a 10' span @ 16" o.c., 5/8 ply subfloor under Ditra would be marginal, though I'd be confident it would suffice if you didn't have any heavy point loads on the floor. A 3/4" subfloor is more than substantial in your case. Ditra is an outstanding product.
According to Schluter, you are ok going over 5/8" as long as it is plywood. NOT OSB. (That would have to be 3/4"). Your deflection can't be more than 1/360th the length of the room. e.g. a room 15' would be 180" divided by 360 gives you at max 1/2". Cut that in half for natural stone( /720).
Ditra is unlike any of the CBUs in that it acts as an uncoupling layer, allowing the subsurface to move independantly of the top layer. Think like a layer of gravel under concrete. If you are going to use a heat mat, it must go under the Ditra.
What concerns me more is the amount of times people are concerned with their floor height. Unless you have an addition in which the subfloors are not at the same height (and they should be) the layers on top should be close. I always tell my associates that a finished floor should be 1 1/2" thick. A 3/4" hardwood over a 3/4" plywood subfloor = 1 1/2". You can't change that, so that's the minimum. It's where you vary from that that we get issues.
Based on what you said ... 2x10 @ 16" spanning 10 ft max, your deflection is L/850.
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt