Porcelain Tile - Exterior - Freeze / Slip Resistance / General Questions

[dwzemens]

After thinking about if for a year, I am going to start a project at my son's home tomorrow. Long story, but I am putting porcelain tile down over an 11' x 4' concrete slab front porch. Ditra will be underneath with Kerdi banding on the edge and folded up the first course of brick on the adjacent house wall.

This is an exterior application in Michigan subject to hard freezes. Here's the info on the porcelain tile. I'm worried about "slipping" on the wet exterior tile. How do these specs look for both slipperiness and resistance to freeze/frost?

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P.E.I. Rating IV has high resistance to abrasion and is suitable for heavy-duty residential and commercial floor installations, such as entrances, commercial kitchens, hotels and exhibition and sales rooms with some dirt conditions
Impervious tile has water absorption of less than 0.5% for indoor or outdoor use and is frost proof
Slip-resistance/Coefficient of Friction rating of .55 wet is marginally skid resistant for indoor use and is recommended for standard residential applications
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Any advice or comments about this would be great, including tips on installing on a 50 year old concrete slab. Great condition, no cracks, etc.

Thanks again!

[bbcamp]

Your tile would be OK except that the coefficient of friction needs to be something like .60 to .75. There are topical solutions to raise the coefficient of friction to make them less slippery, but it's best to start with one that isn't slippery to begin with. Focus your search for pool deck tiles. An alternative is to use a smaller tile with more grout lines and line width for traction.

Does the current porch have adequate slope for drainage (1/4" per foot)?

Is the slab clean and ready to accept thinset?

[dwzemens]

Thanks for the info Bob.

Unfortunately, the slope is not quite that good at all. What issues will I be finding as a result? Obviously, the old concrete would wick the moisture into it (which is part of this issue because it's over a finished basement space and was leaking), so this fix is really not for aesthetics, but I figure it will make the slap water tight.

[bbcamp]

Slope will help by removing the standing water. That helps with freeze resistance.

The slab can be topped with deck mud to provide slope. Look at the Ditra Handbook for the "Concrete or Wood Substrate Over Occupied Space" detail. A lot of their proprietary extrusions can be eliminated or replaced by clever tile work, but the main feature is a sloped mortar bed, a drainage mat, another setting bed, then Ditra with Kerdi flashing. This stack up will require about 2 to 3 inches. You will need another 2 or so inches to the bottom of the door threshold to properly flash that area.

I suppose you could skip the drainage mat, considering the Ditra is supposed to be water proof. You will need a sloped mud bed of about 1 inch thickness at the house and tapering to nothing at the edge of the porch. This would be bonded to the slab with thinset. So, you would still need about 3 inches from bottom of door to top of slab to start with.

[dwzemens]

I have taken a look at that Ditra handbook and see all the layers, but I have to be honest: I'm only going with the Ditra and Kerdi band on the inside edge because that's really where the water leaks: down the seam between the porch slap and the house.

Plus, there's just no real way I could add that 3-4" height and not have a stairway step height issue onto the porch. There's only one step, but adding that extra height would of course through off the correct ratio and present a trip hazard.

So ... this is a retrofit and I am just trying to make it "good enough". If you know what I mean.

[cx]

Dave, the only membrane with which I'm familiar that is indicated by its manufacturer for use as a single waterproofing layer under a tile installation over occupied space is Noble Company's Noble Deck. I'd want at least that in your situation.

Still requires the minimum quarter-inch per foot slope of the subfloor, though.

Using something like KerdiBand to flash up the exterior of that brick veneer (I'm assuming) wall will cut down on surface water entering that slab/wall joint, but it's not gonna make it waterproof. Likely the best you're gonna be able to do under the described circumstances, though.

My opinion; worth price charged.