I am finishing an outdoor screened in porch. The windows are screened with a product called Weather Master so the room will not get wet when raining. However the room is not heated and will experience the cold temps of northern Ontario. I have purchased ceramic tiles for the floor. The floor is pressure treated plywood. The room is 115 sq.ft. What is the best method to install the tiles.

Thanks
Hosh

Hi Hosh,

So you're saying this special screen will not let water in? I thought Weather Master was a brand of windows. I've never heard of "magic" screen.

I'll need more info as to how the framing is built and with what. How high of the ground. Type and size of joists, species of wood, grade, on center spacing of the joists and unsupported span of the joists to the inch. This is to verify the floor is stiff enough for tile. Sometimes people build a room on an old deck which usually doesn't meet standards for tiled floors.

I can tell you that the pressure treated plywood is the worst thing you could have chosen as the subfloor. It's very unstable, (unless it's kiln dried) and is not for interior use. It'll probably be OK to keep it, but you'll want to cover it with the proper plywood underlayment and then concrete backer thin setted to the ply, or Ditra matting. The tiles should be a frost proof type, such as porcelain. There's much more to it. Lets start with the framing info.

Jaz

Jaz is right! Any photographs? Plywood will not cut it And its a outdoor porch, it will be tested by the weather.

Okay, I know a little bit about this. First install a kerdie membrane over the plywood and seam all joints, than install your ditra membrane over the top of this and seam this, allow for a "bara flashing" by schulter if needed. If you have any water penetration at wall areas be sure to install kereick first before the kerdie. This method only works for porcelain tile or ceramic, stone applications require another spec. You must also provide for an expansion joint if your project is less than 8-12 '

Hewittile,

Where did you get that info from? Since when do you install Kerdi over ply and then Ditra? That's all wrong or did you misspeak.

Jaz

Jaz, sorry it took so long to get back, check with your schluter rep, this is the prefered method of installing porcelain tile over plywood at a deck area. Once again, kerdie, ditra,and the tile. This is what my Western rep told me, also I do have the paperwork on this and will dig it out when I can. Currently am in the process of installing porcelain tile at an exterior deck using this same process.

The Schluter handbook specifies Ditra, Kerdi on the seams, then tile. There are a number of approved substrates (eight, to be exact) for Kerdi. Plywood isn't one of them.

I agree with Kman. Never seen or heard of the method hewittile is describing.
Hope Hewittile can back up that method with an actual Schluter written specification.

Until such time I would ignore that method.

Okay ! I agree with kman and all who say that until hewittile can back that up with specs, forget about this method. I am looking at the schluter systems now, you will find this method under " ditra drain" at the schluter web site. I probably was not clear enough when I said " ditra" this is their drain system and still un uncoupled membrane, I will let you know in a couple of years as I am installing tile at an outdoor porch using this method. The schluter rep... 888-8531

Sorry I have no clue what your looking at.

The approved method is very clear in the Ditra Handbook specifications for exterior porch installations.
The only reference to Kerdi is for banding the seams only and the wall transition on Ditra.

RC ! got you, I agree, A person can use the " ditra drain" but not the "kerdie" because there is no proper tile substrate for the kerdi since this deck is plywood. My only question is, has any tile expert and installer ever installed tile at an area that was not by the book ?, and it worked. I still maintain that installing kerdi over plywood using say " laticrete 253 " works just fine even though its not by the book. If all tile experts go by the book and thats all where are we as forward looking contractors ? If I can't prove a certain installation method because it's not by the book, does that make it wrong. Just a note, the schluter rep, off the books says that installing kerdi over plwood and than the ditra drain, probably is acceptable. The only drawback would be " the guarentee ". I will still give my opinions based on my knowledge and can only hope this helps to provide answers to questions in the future. Thak You to the senior members on this.........

What is "ditra drain" ?

I can't see how installing Kerdi over plywood can possibly work. There's too much potential for movement in the plywood for Kerdi to be able to compensate. Kerdi is strictly a waterproofing membrane that must be applied to stable substrates. Plywood is not one of them.

Your Schluter rep should be fired for making those statements.

This exterior deck is 1" 1/8" plywood, what if I used redguard then seamed than the ditra drain mat over ? Also ditra drain mat is somewhat like schluters troba mat. I am trying to get another layer of waterproofing underneath the ditra as back up.

I think we need to clarify terminologies.

To my knowledge Schluter Ditra Drain was or is only available in the UK.

As far as I know there are only two types of Ditra available in North America, regular Ditra and Ditra XL. Both are uncoupling membranes only.

Here in this part of the world there are only two mats classified for drainage and they are Troba and Troba Plus.Each with their own characteristics.

Please correct me if I'm wrong on the availability of Ditra Drain in North America.

It would be your call Rick if you want to use a liquid membrane in your hybrid assembly. You and you only are the one who has to warranty the system your creating.

Whether it may or may not work is anybodies guess. We on this forum try to keep all answers to questions inline with manufacturers specifications and industry guidelines as specified by the TCNA and TTMAC

I don't think anyone is going to go out on a limb and tell you what you want to here.

According to one of my tile suppliers I can get " Ditra Drain Mat" after August of this year, I actually have a quote on this product.I better call again and check. Looks like a good product. I actually quoted an outdoor balcony based on the fact that I could aquire this product. Good luck I guess. Thankx