Subflooring thickness


Old 03-05-07, 05:44 AM
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Join Date: Mar 2007
Posts: 6
Post Subflooring thickness

Hi....I have been readng a lot of threads on subfloors and just want to confirm some info.

I am tearing out all flooring down to the floor joists in my 1875 home...

QUESTION: for the kitchen and bath I will use cermaic tile. Is this configuration right?
3/4'' plywood OSB, roof felt, 1/2'' concrete board, then tiles???

For the rest, I will use hardwood flooring.
QUESTIONS: Is this configuration correct?
3/4'' plywood OSB, roof felt, then 3/4 hardwood flooring?

thanks for your help!
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Old 03-05-07, 07:53 AM
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Join Date: Mar 2005
Location: USA
Posts: 43,837
What was the thickness of the original floor?

Usually walls are built over the sub floor so when you remove the sub floor there will still be old flooring under the walls. Were you able to remove all the sub floor right up to the walls? If not you may need the new sub floor to be the same thickness.

Unless I'm mistaken, cement board is supposed to be installed over an thin [troweled with grooves] layer of thin set mortar and then screwed in place. The thin set takes up any voids under the cement board.

The rest is correct.
Old 03-05-07, 11:57 AM
Join Date: Dec 2005
Location: massachusetts
Posts: 67
5/8" subfloor is code, tile may require thicker.
Use 1/4" hardibacker or CB for floors
Old 03-05-07, 02:06 PM
Join Date: Jan 2007
Location: Central Indiana
Posts: 389
Agree with marksr, leave out the roof felt between the concrete board and OSB, and bed the concrete board with thinset over the OSB, then screw it (or air nail with roofing nails).

Tile Council of America (TCA) has a $7 (or so) handbook of approved installation sandwiches (for lack of a better term) that may be of help to you.
Old 03-05-07, 05:48 PM
Thread Starter
Join Date: Mar 2007
Posts: 6
Subfloor thickness

thanks again for your help. My farmhouse actually has NO subfloor at all so removing it from under the walls is definitely not an issue. There is insulation between the joists but I plan to remove the temporarily remove the insulation before next winter and install strips of plywood from below in between the joists & reinsert the insulation.
Old 03-05-07, 06:00 PM
Thread Starter
Join Date: Mar 2007
Posts: 6
Subfloor thickness

Oh....just to clarify....I am only remodeling about a fourth of the house....and the existing planks in the other 3/4 luckily leave plenty of room (thickness) to match the height of the new sub/flooring. What I am ripping out is thinner porch planks in one area and very thin plywood in another that is very wavy....THANKS AGAIN FELLAS!

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