7 posts / 0 new
Last post
mitsuman35
sub floor for tile
mitsuman35

I am going to install porcelain tile in my kitchen but I want to make sure that my subfloor is strong enough so that I don't have any problems once the tile is laid. I have a 1950's ranch that has 6 inch by 3/4 inch tongue and groove plank subfloor, I was thinking of adding a layer of 1/2 inch playwood that I will glue and screw in place. What I want to know is that going to be strong enough and should I use 1/4 or 1/2 inch cement board on top of that, also should I put down thinset before I put down the subfloor or not? Any help with this would be appreciated.

HoustonRemodeler
Re: sub floor for tile
HoustonRemodeler

More importantly we need to know if your joists are up to speed first. For the best tile information, head over to the John Bridge Tile Forum and use the handy dandy deflecto-meter linked in the dark blue bar to calculate if your joist can handle tile. Then we can get to the planks and plywood.

dj1
Re: sub floor for tile
dj1

You will need to know your joist dimensions in order to use the deflection formula. See if you can crawl under the house to find out.

mitsuman35
Re: sub floor for tile
mitsuman35

Thanks for the responses, the structure under the floor is 2x8's that are 12 feet long I will be sistering them with 2x8 doug fir. I used the delectolator and got a measurment of L/603 after the sistering. It appears that is going to be ok according to the deflectolator. Any additional help would be great.And thanks again.

HoustonRemodeler
Re: sub floor for tile
HoustonRemodeler

Screw down the planks to the joists.

Orient the face grain perpendicular to the joists

Screw down the CC grade or better plywood to the planks and not the joists. (BC is usually easier to find, T&G is optional)

Be sure to use thinset under your CBU before screwing down the CBU to the floor.

Offset the CBU, installing them like bricks.

Gap the CBU sheets 1/8", use an alkali resistant mesh tape and fill the joints with thinset

Use Backer-on CBU screws (or similar) and an impact driver to set the screws in the CBU

Tile the floor before setting the cabinets.

If you are setting a natural stone as your tile, you need a deflection of L720 and 2 layers of plywood.

Buy John Bridge's book on installing tiles as this is just the beginning on the 400 questions you'll have. The good folks on the John Bridge forum will be able to give you more detailed, speedier answers. Plus you can post pictures there a whole bunch easier.

mitsuman35
Re: sub floor for tile
mitsuman35

What size cement board do I need to use 1/4 or 1/2 inch?

HoustonRemodeler
Re: sub floor for tile
HoustonRemodeler

1/4 inch is plenty. CBU provides zero structural support. Its merely a tile-able surface.

Sponsored Stories

TV Listings

Find TV listings for This Old House and Ask This Old House in your area.