Greetings:
I have an area off my attached garage that serves as an entry wall and on either side is a powder room and a laundry room. The total square footage is 125 sq. ft. and the subfloor is t&g OSB and I think it is 5/8″. The adjoining floor area is carpeted – but ultimately I want to have hardwood floor installed where the carpet current is.
I have selected some ceramic tile and need to choose an installer. One installer wants to use Jame Hardie backer board screwed to the subfloor and then tile over that. The other installer wants to first install 1/4″ underlayment and then Ditra decoupling flexible underlayment over that. His reason for the plywood underlayment was to provide enough final thickness such that when I have hardwood installed down the line, the tile will exactly match the tile level. He is not fond of James Hardie backer board and is not inclined to use the thicker Ditra XL product to avoid plywood underlayment altogether.
Which approach for my situation do the pros here favor? Does the plywood approach gain me extra structural support so grout is less likely to crack?If I choose the fellow that likes the James Hardie product, do they make thicker boards to ultimately achieve the same final thickness as with the Ditra approach?
Thanks in advance for any help.
Replies
I don't see much of a difference except to say that 5/8ths over 16 oc 2x8s or 2x10s is probably not enough stiffness for tile, if this a raised foundation. I'd address that first.
The other details are really no big deal. I've used both Ditra and Hardi in my home.
Thanks Scooter1
I should have mentioned this is on my ground floor and there is a full unfinished basement below. For what it is worth, neither installer mentioned a need to beef up the subfloor with any stiffeners, etc. Also, all the heating duct work is directly below this floor since the furnace is located in this corner below the laundry room. It would be impossible to add any stiffening to the subfloor from the basement without removing lots of ducting.
Regarding your concerns for the stiffness, is there an advantage then in going with the 1/4" plywood plus Ditra approach to take adantage of added stiffness from the added ply?
A quarter inch of anything will not add any stiffness. Your installer needs to run the deflection through the Deflecto-Meter, with the species of the joists, size, and decking thickness to see if your floor provides enough stiffness. You provide no information as to this, so really, what goes on top is premature at this point.
Stiffening up a floor without changing out joists is not a fun project--I've seen 2x4 used under the joists and extra beams below as well. But it all comes below, not above. Regards, Scooter "I may be drunk, but you're crazy, and I'll be sober tomorrow." WC Fields, "Its a Gift" 1934
Thank you for educating me about the Deflecto-meter. I was aware of L/360 rules but not a way to calculate it. I found this on-line calculator but there is no input for sheathing thickness. ?? Is the calculation independent of thickness?
http://www.johnbridge.com/vbulletin/deflecto.pl
Edited 10/12/2009 1:31 pm ET by Will92
Thats because, as I said, nothing you put on top of the joists will affect stiffness. Everything is from below, e.g., joist size and spacing and support beams for the joists.
That being said, my experience is when one adds an inch an eighth t&g floor, often called a Sturdy Floor, that does add stiffness, but its not supposed to be counted.Regards, Scooter "I may be drunk, but you're crazy, and I'll be sober tomorrow." WC Fields, "Its a Gift" 1934
First, I'm no pro but I've done similar to what you want in my home.
Plus my neighbour is a Certified Building Envelope Specialist and runs a build/reno company that is considered in the top three/four in my area. He helped me with my reno, improvements and I consider his advice to be good.I laminated ripped plywood to my joists from below, a sheet on each side. Attached using PL and screws. I also did the X brace thing where ever I could do so. You cannot overbuild a tile underlay system, I feel.
Strong and stiff is good.My tile is over Ditra which is over a plywood sub over the original sub (which was ply, not OSB) and looking and living with how that works and how it matches up in transition to other flooring materials, I'd do it no other way.Solid floor (I've walked on tile that did not feel solid), warm floor (electric in floor radiant), no, none, zero grout issues and the "look" is very tight, seamless. Hope this helps.