floor height differences between rooms

18 years ago

Hi,

I have been reading hundreds of posts and articles on the subject of tiling, backerboards, installation, tips, techniques, etc. but have not gotten enough detail to answer my question sufficiently enough. I have been remodeling my kitchen for the past couple of years doing all of the work myself. Have gotten through all the mechanicals (plumbing, electrical, heating, lighting), brought the walls and ceiling back up and have finally painted and am ready for my floor.

The room is 12 x 17 with 2 x 8 sistered joists running across the length of the 12 ft span at 16" o.c. I have 1/2 in. of plywood down now. I will be using 3/8" 13 x 13 glazed porcelain tiles.

Based on what I have learned, I will need to put down at least another 5/8" exterior grade plywood to bring the height to 1 1/8". With 1/4" backerboard this will bring the total height of my kitchen floor at least a 1/2 inch higher than the adjoining living room wood floor. Now this is without taking into account the thinset underneath the backerboard and under the tiles. Now for my questions:

- Based on recommendations, I will be attaching the second layer of plywood at a spacing of 6" intervals. Thats well over 100 screws/nails per board. Ringshank nails seem like they would be easier/faster to use vs. screws. What do you guys use?

- How much height will thinset add to the floor?

I am considering using Ditra which will help me an lose 1/8" and really only increase my costs by about $50-$60.

I am wondering the best ways to decrease the height without sacrificing a quality install.

- What would be considered too large of a height difference between rooms and/or what is considered acceptable and what would be the best way to handle the transition between the different levels. Sorry for the length of this post. Thanks for all your feedback, it is really appreciated.

Mark

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Comments (4)

jerry_t
18 years ago
Your 1/2" subfloor is most likely a CDX grade and not T&G'd. Thats a real problem underneath tile because the middle plies have voids throughout each layer. I would make sure the 5/8" underlayment is a BC or AC grade. Ditra is what I would use.

I don't know how many sq.ft. you have but it may be feasible to take up the subfloor and just use a single layer of 3/4" T&G plywood.
jerry_t
18 years ago
I have ADD :). The best way to transition down is to use a wood mini reducer. The tiles must have good clean cuts and place the "fat" part of the reducer against the tile and it would slope down resting on top of your wood floor. They come in various thicknesses and either prefinished or unfinished.

I leave a gap between the tile and reducer and fill that with color matched grout caulk.

See picture 14

Here is a link that might be useful: Mini reducer - picture 14
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marklevinson1
Original Author
18 years ago
Jerry,

Thanks for your response. I have around 230 sq. ft. I might be mistaken but isn't there a minimum thickness of around 1 1/8" required below tile to minimize deflection? I can definitely understand the use of t&g for stabilization of the floor. Too bad they don't make a 5/8" t&g panel. Thanks for the link to the reducers that really helps clear that up.

Mark
jerry_t
18 years ago
They still make a 5/8" T&G plywood subfloor, Lowe's item #12250.

You are a little confused about the minimums for a plywood substrate. The minimums are this for joisting 16" OC.

If installing tile directly to plywood the minimums are the subfloor (bottom) layer to be 19/32" T&G subfloor rated plywood with a layer of 15/32" sq.edge plywood underlayment installed on top... equaling 1 1/8". This is for residential, light commercial settings state both layers to be a min. of 19/32" thick.... equaling 1 1/4" thick.

If you are incorporating either CBU backerboard or Ditra membrane between the tile and plywood the minimums drop down to a "single" layer subfloor using a minimum of 19/32" T&G subfloor rated plywood.

Those are the absolute minimums as far as plywood substrates go.

I personally go thicker in both cases. Bottom line is 3/4" (23/32) T&G subfloor rated plywood is OK to use underneath CBU or Ditra.

These minimums are straight from the Tile Council of North America 2007 Edition Handbook.