tiling exterior covered porch with 3/4" osb subflooring

nocarpenter · 06-10-2009, 11:14 PM

I am getting ready to start an exterior tiling project and could use some advice. I have a 8'x20' exterior covered patio that I am planning on installing porcelain tile over. The patio is covered on 3 sides and unless it rains and wind blows hard which it did last night, not much of any water gets on patio. I was planning on simply installing 1/4" concrete tile backer board to 3/4" osb subfloor after putting down thinset between osb and tile backer board, then installing tile over backer board then installing epoxy grout. Friend of mine thought i should install a coat of redguard to protect subfloor just in case. Any thoughts or suggestions would be much appreciated. We are in north central washington state so we do get freezing and snow.

JazMan · 06-10-2009, 11:57 PM

Chances are your project is ill fated if the proch was built the standard way.

Need to know a lot more info on how it's built, type & size of joists, spacing, span, species & grade. How level it is, which cement backer you're planning to use, and is the OSB guaranteed for exterior use. More to it than that, but let's start there.

Jaz

nocarpenter · 06-11-2009, 10:21 AM

Quote:

Originally Posted by JazMan

Chances are your project is ill fated if the proch was built the standard way.

Need to know a lot more info on how it's built, type & size of joists, spacing, span, species & grade. How level it is, which cement backer you're planning to use, and is the OSB guaranteed for exterior use. More to it than that, but let's start there.

Jaz

Ok. beneath the 3/4" osb are TJI floor joists 16" on center. then my crawlspace is below that. My roof overhangs patio 2' on end. Basically I my house is 3 sides of this deck area and bottom of roof trusses are my ceiling to my deck.

JazMan · 06-11-2009, 04:12 PM

If the joists are not over spanned you should be OK in that regards. I'm assuming they span about 8' or less. Is the floor pitched for water run off? Outdoor tile project require a minimum pitch of 1/4" per ft., 3/8" would be better. We rarely find that unless it was built with tile in mind.

If the floor meets these requirements, you can do as you said and also apply a waterproofing membrane as suggested. The best would be Ditra, but it costs more. Which backer board are you considering? Does the porch get sun much of the day?

Jaz