# Porcelain Tile on a Wood framed Exterior Porch



## jmckay (Sep 21, 2009)

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!!


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## ChrWright (Jul 17, 2007)

jmckay said:


> 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!!


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?


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## A and K (Sep 20, 2009)

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.


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## WarnerConstInc. (Jan 30, 2008)

I have tiled several screened porches here in northern Indiana but, they were all on a slab.

I used Daltile that said it was for use in/outdoors, karabond karalastic mixed with milk (100 bucks everybag you mixed) epoxy grout.

First one was done 3 years ago and still looks like the day I finished.

The wood framing outside is the part that would bother me.


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## jmckay (Sep 21, 2009)

ChrWright said:


> 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?


 
Thanks for your feedback. I'll address with homeowner and go from there. If he goes back to his orginal idea of outdoor carpet do you know of any exterior grade floor levelers that I could use to float all of the plywood seams prior to carpet glue down? I've used the interior leveler but don't know how it would hold up with Indiana temperature swings and moisture. Thanks again!


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## jmckay (Sep 21, 2009)

A and K said:


> 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...
> 
> ...


Great. Good info here. Thanks for taking the time to share your thoughts.


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