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nvstewar 09-21-2012 11:42 AM

Tile in enclosed porch
I'm planning to tile in my enclosed porch. Subfloor is concrete (pre-existing). Subfloor resides over finished basement.

I've removed the previous tile. It was a thick terracotta set in a strong concrete/mortar like mix. Demolition hammered it all out, scraped the floor mostly flat and have leveled it all out with self leveling.

I live in Ontario. Freeze thaw considerations required.
9'x9' porch area.
There's a couple small cracks that were filled in with the self levelling. Nothing major, although some had transferred to the removed tile.
The house is OLD. I think the old tile had been there 20+ years, and I don't expect settling/vertical movement to be significant.
The porch is fully enclosed. Roof, brick kneewall, aluminum/windows. it won't be exposed to the weather, but will see wet from foot traffic.

So my question:
Do I need to consider plywood, backerboard or membrane on top of the concrete subfloor, or should I be o.k. tiling directly on it?


JazMan 09-21-2012 08:29 PM

Hi Norm,

First of all it sounds the space is not heated, so you're running out of time without auxiliary heat. You need to have the floor at 50 f.degrees or higher, that's 10 c., not just the air, but the concrete.

You should use a porcelain tile rated for outdoors and the appropriate thinset mortar for the installation system you select.


Originally Posted by nvstewar
So my question:
Do I need to consider plywood, backerboard or membrane on top of the concrete subfloor, or should I be o.k. tiling directly on it?

Definitely you can not consider plywood or backerboard on concrete, but a membrane would be smart. Ditra would be a good idea, or a liquid membrane at least.


nvstewar 09-21-2012 09:41 PM

Thanks for the feedback Jaz.

I'll price out the difference for Ditra vs Redgard for the area.

How long many consecutive days of 10C+ temps do you suggest for thinset + grouting?

Our days have been pretty nice, but the nights are starting to cool of pretty good already. Looks like I might get a pass on this project till springtime. I guess this means I'm gonna have to bash down that chimney now:)

JazMan 09-21-2012 10:03 PM

I would want the concrete to be at least 50 at night for min 3 days before and a week or two after. Actually for a month after would be best.

Compare Ditra to Redgard if you wanna, but you're comparing apples to orange juice. Remember you'll probably need 2 coats of Redgard equaling a certain mil thickness per directions.


nvstewar 09-21-2012 10:20 PM

Thanks. I appreciate the help.
Sounds like it'll be a springtime project at this rate.

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