Replies

1. 
   Notchman | Jul 22, 2005 04:45am | #1

   Personally, I think Hardy board is nice tile substrate for countertops and entries and such, but I prefer that miserable Durock or Wonderboard for wet areas, like baths and showers....and decks.

   And now, after a good first experience with Ditra, I plan to explore its use as an exterior tile substrate.

   The only exterior waterproof tiled decks I've been involved with consisted of a heavy frame, PT ply, a membrane (don't recall type) and a 2" concrete slab....all engineered and in perfect shape after about 11 years....I just helped with it....wasn't my project.

   I do build walk-on decks and have discussed them here, but the the materials and method I use probably wouldn't work for tile.

   Try http://www.johnbridge.com

    

2. 
   menken | Jul 22, 2005 05:01am | #2

   Yea. Forget the Hardi. Just use Ditra. No screws to screw up your membrane. Ditra works.

3. 
   Wango1 | Jul 22, 2005 06:25am | #3

   Hey-

   Try looking at Schluter.com for info on exterior tile applications. Also the Tile Council of America has the guide on all installs.

   Incidentally you cannot use Hardibacker outside!!!

1. 
   PapaDave | Jul 22, 2005 08:57am | #4

   Thanks all, I checked out the web sites, and now I am thinking:Tarpaper
   1/2" cement board
   Thinset
   Ditra/Kerdi
   thinset
   TileThis sound good, or should there be a thinset mortar bed under the cement board as well?Dave

1. 
   Wango1 | Jul 22, 2005 03:20pm | #5

   You don't need the tar paper, next yes you will need mortar under the CBU, and then it is overkill to do CBU AND Ditra (one or the other is fine). Schluter makes a Kerdiband that goes with the Ditra to waterproof.

   My concern is putting the CBU outside--that's a no-no. 

1. 
   WorkshopJon | Jul 22, 2005 03:44pm | #6

   "My concern is putting the CBU outside--that's a no-no. "

   Why?  I thought it was waterproof.

   WSJ

1. 
   Wango1 | Jul 23, 2005 12:25am | #10

   NOOOOO! It is water impervious --- not waterproof. It is unaffected by water, it can sit in it for years, but it will not hold it back; water will pass right thru it. Hence the need for the Ditra or similar. Ditra when combined with Kerdi will be water proof.

   This is a common mistake/misnomer among non-professionals. CBU's are only there for strength and stiffness. They do nothing for waterproofing!

2. 
   PapaDave | Jul 22, 2005 08:32pm | #8

   Well, the folks at Schluter show the CBU, then thinset and the Ditra with Kerdi on the seams for an exterior deck detail...

   is this overkill?

    

   Also if we mortar under the CBU, do we need some metal lath screwed to the plywood?

   Edited 7/22/2005 1:38 pm ET by Dave

1. 
   Wango1 | Jul 23, 2005 12:57am | #11

   No I don't think it's overkill at all.

   I also don't think you need metal lathe at all. Just follow Schluters instructions. Be sure to have your building inspector look at it.

4. 
   timkline | Jul 22, 2005 04:45pm | #7

   i've been asked this before, how do i put ceramic tile on my deck with living space below ?

   my response is mostly, you don't.

   how much profit do you have built into the job ?

   if the deck leaks, what are you going to do about it  ?

   accessing the membrane means ripping up the tile and doing the whole job over.

   inaccessible membranes to me involve huge risk and liability.

   my recommendation is don't do this.

   if you choose to do it, take every precaution possible. this means installing a quality membrane roof system designed for low slope. follow this with an uncoupling membrane  (ie Ditra) for your tile base installed as per manufacturers recs to ensure that there are no compatibility problems between the roof system and the Ditra.  NO penetrations are allowed in the roof system. Sidewall flashing is critical.

   good luck

    

   carpenter in transition

1. 
   PapaDave | Jul 22, 2005 08:36pm | #9

   Thanks Tim.

   I reread my original post, and it was a little confusing.  My deck is not over living space, they are stacked exterior decks, the top one being covered by a roof.  Each deck acts as a roof for the deck below.  The lower deck acts as a roof for an exterior patio on a daylight basement.

5. 
   Scooter1 | Jul 23, 2005 01:59am | #12

   I'll be a naysayer here--your deck is doomed for failure.

   I treat all 3 season porches, decks, sidewalks, and patios alike--they are all exterior structures and deserve exterior products and adequate drainage and slope. So no Hardi.

   From the subfloor up, this is what I would do: Subfloor, Sloped Mortar Bed Preslope (quarter inch per foot), Sheet Membrane (40 mil at least), Drainage Mat (like Schulter's Troba), 1 inch mortar setting bed, and finally tile. The Preslope should slope to a scupper or the edge of the deck or to a gutter.

   You don't say where the deck is--but if it freezes there, you really really need good drainage and a drainage mat.

   I think the idea of screwing Hardi through the waterproof membrane is nuts--hundreds of holes in your waterproof membrane?

   Check Hardi's Web Site--it is not suited for exterior applications, especially in a freeze thaw state.

   My two cents.

   Regards,
   Boris

   "Sir, I may be drunk, but you're crazy, and I'll be sober tomorrow" -- WC Fields, "Its a Gift" 1934

1. 
   PapaDave | Jul 23, 2005 03:23am | #13

   Boris,

   Thank you for your help.  I have run across your comments in other threads and found them very helpful.

   What is the difference between the Ditra and the Troba?

   Is the troba only a drainage mat, or are you doubling up on the waterproofing layers?

   Shluter shows a 1/2" CBU in their Ditra cross section for an exterior deck.  A check of Hardie's website in fact confirms it is not rated for exterior use...so is there another 1/2" CBU that is acceptable?

   Portland, OR  so no freeze to speak of, just occasional 3 or 4 days.

   I agree, the idea of the screws through the membrane gives me the hibbie jibbies. But will a thinset grab the slippery surface of the membrane enough to keep everything secure and in place?  It looks like the Ditra solves that concern with the waffle tread, and fleece.

   Thanks again,

   Dave

1. 
   Scooter1 | Jul 23, 2005 03:50am | #14

   Troba is a drainage mat--it is an orange waffle shaped mat with holes in the waffle holes which is at the bottom of the setting bed. It allows the setting bed to drain onto the membrane. Its like a strainer under a pile of spagetti.Ditra is a anti-fracture membrane, but is unique in that it is applied onto the setting bed, instead of under the setting bed. It is not waterproof. It is plastic, so it is sorta water resistant, made more so if one uses a waterproof tape called "Kerdi" to seam the edges, but I repeat is not waterproof. It is not a substitue for a waterproof membrane and is not used in showers. Ditra's highest and best use is over plywood, as it prevents the tile from expanding and contracting at the same rate as the plywood and is very thin, about an eight of an inch, so it is great where elevation issues are important. Essentially it is a subsitute for any backer board, like Hardi backer.Did I say that Ditra is not waterproof? Schulter does have surface applied membrane like Ditra that is applied to the setting bed called Kerdi, which in fact is waterproof and is used in showers. If I were spec'ing out your job with Kerdi, I would still want a preslope or sloped mortar bed onto which the Kerdi would be applied and therefore the water would flow out to air or a scupper or a drain of some sort.I don't use much Schulter products down here--they aren't Code, but they are terrific products, and I hardily recommend them. But if you are contemplating Kerdi, I would contact Schulter's Tech Service people to make sure it is fine for a quasi-exterior deck. I would suspect the answer would be yes, but check and see.I am a traditionalist, so I would probably recommend the preslope, a sheet membrane like Compseal, Nobel etc over the presope and a standard sand portland cement setting bed. Sand and cement is super cheap, and any such deck would be as good as any made with Kerdi and about half the price. It is also easier to find subs that have worked with mortar. Schulter products are still "new" here in the USA.Good Luck, and ping me on the BB or privately if have any questions.Regards,
   Boris"Sir, I may be drunk, but you're crazy, and I'll be sober tomorrow" -- WC Fields, "Its a Gift" 1934