Porcelain Tile On A Wood Framed Exterior Porch

Originally Posted by jmckay

I have a customer who's hired me to build a screened porch. The overall size of the porch is 14 x 20 and the foundation is built with 2 x 8 framing because of low ground clearances. There is a ledger attached to house, a double beam in the middle of the framing (parallel to the house) and a double beam for the rim joist (so the longest joist span between beams is approximately 7 feet). Joists spaced 16" o.c. The subfloor is covered up with 3/4" exterior plywood and is blocked at the seams since it wasn't available T&G. The homeowner had planned to use outdoor carpet but has now asked me to lay down porcelain tile and/or slate. Just want to be sure that this scenario: exterior (but covered), freezing and thawing (Indiana) and wood foundation described above would adequately support the tiles. I would probably install a 1/4" tile backer over the plywood subfloor first. Any advice or cautions....? Thanks!!

Originally Posted by Leo G

Thanks for that tidbit of information Darcy.

Originally Posted by ChrWright

I wouldn't recommend installing any tile outdoors over a wood substrate, even with a tile backer over it. Despite the fact that it's covered, it's still going to be subjected to extremes of temperature and moisture. I'm also in Indiana, and I've seen more than a few grouted installations--even over concrete--that crack and fail within a couple of seasons.

Drainage is another issue. Even if you water proof the installation, how will you prevent moisture issues at the perimeter?

Originally Posted by A and K

If proper measures are taken and correct materials are used, you stand a much better chance of an acceptable outcome. The grout will more than likely discolor or oxidize because of moisture and climate changes.

This seems elementary....but you would be surprised how often it isn't the case...

Make sure the deck slopes away from the house! If it has no slope...you can add some to it, to ensure proper drainage...If it slopes to the house...you will need to mud it.

It is imperative that flashing be used where the deck meets the house, as well as under the membrane on the outside edges.

There is a "self sealing" membrane that can be applied to the plywood.

We always thinset and then screw down the backer board.

Next...you must find in your area exterior approved waterproofing for extra insurance.

Investigate the brands and types of thinset available to you...ask questions...call the rep...get the best thinset for this application.

Mix grout correctly and seal with high quality sealer.

Choose a tile rated for extreme weather. (Porcelain...full or color body is best.)

I always suggest a "slate look", textured or stone look with some texture....to help prevent slipping when the tile gets wet.

Don't do wider than 3/16" grout joints.

Caulk to the house instead of grouting...but make a nice close cut.

Use at least a 3/8" trowel and check well for adhesion.

This can work out fine for both the installer and the homeowner. It does look great...and it is not difficult to do.

I hope that this helps.