Welcome to the DoItYourself Forums!

To post questions, help other DIYers and reduce advertising (like the one on your left), join our DIY community. It's free!

How finish off deck tile job


debeze's Avatar
Member

Join Date: Dec 2012
Posts: 95
CAL

12-06-17, 08:03 PM   #1 (permalink)  
How finish off deck tile job

I am pretty well done rebuilding my elevated deck and am including a 32" X 72" tiled area to hold a Weber kettle and a heavy Egg type cooker. The substrate is 2 sheets of PermaBase Durock type cement board, 1/2" thick each, glued together. Lower board is screwed to joists. Isolation around the edges to deal with shear. I have been advised to put the tiles down directly on that using premixed SimpleFix adhesive + grout.

Do I really need a membrane for an area so small? Any other issues??

This is a small area. No need for movement joints. No one will walk on it....

8" square porceilain tiles, 1/8" spacing.

Here is a picture.

THanks so much!!

Attached Images
     

Last edited by debeze; 12-06-17 at 08:04 PM. Reason: typos
 
Sponsored Links
Marq1's Avatar
Member

Join Date: Sep 2016
Posts: 1,473
MI

12-06-17, 11:36 PM   #2 (permalink)  
Do I really need a membrane for an area so small?

Like a shower pan membrane?

 
marksr's Avatar
Forum Topic Moderator

Join Date: Mar 2005
Posts: 42,077
TN

12-07-17, 03:58 AM   #3 (permalink)  
What is under the cement board? cement board by itself doesn't have much structural value.


retired painter/contractor avid DIYer

 
debeze's Avatar
Member

Join Date: Dec 2012
Posts: 95
CAL

12-07-17, 10:27 AM   #4 (permalink)  
Underneath I have 4 x 6 joists, spaced 8 inches on center. Lots of screws going through the first course of cement board into the joists. Then I laminated the second cement board on top of the first. Itís pretty stiff when you walk on it Thanks for getting back to me

 
debeze's Avatar
Member

Join Date: Dec 2012
Posts: 95
CAL

12-07-17, 10:30 AM   #5 (permalink)  
Waterproof crack insulation. I could spend $80 on Schluter and throw most of it away, or spend $60 on liquid paint- on membrane and throw most of that away. I wondering whether either is necessary. My architect friend told me to drill three holes through the foot of the cement bed ( it slopes downward) but I am unclear as to why

 
marksr's Avatar
Forum Topic Moderator

Join Date: Mar 2005
Posts: 42,077
TN

12-07-17, 10:34 AM   #6 (permalink)  
IMO there out to be plywood or deck boards under the cement board to give it strength but I'm just a painter, hopefully some of the others will have better info for you.


retired painter/contractor avid DIYer

 
debeze's Avatar
Member

Join Date: Dec 2012
Posts: 95
CAL

12-07-17, 10:47 AM   #7 (permalink)  
Beg to respectfully differ. :>) Plywood is an invitation to rot. Don't really need it. What you are talking about is called "deflection", as you might know. Simply put, if you apply weight, does it bow downward in the center, and by how much? The joists run parallel with the long dimension. Deflection is a function of span. With 8" OC and doublewide joists, there ain't much span here. (I hope!)

 
stickshift's Avatar
Group Moderator

Join Date: Oct 2004
Posts: 18,316
WI

12-07-17, 11:38 AM   #8 (permalink)  
You're not using standard methods here - the plywood you seem to hate - so it may be difficult for anyone to advise. As mentioned, CBU does little to stiffen the surface and 1/4" is considered sufficient for flooring, so I'm unsure what was accomplished with your build.

 
Pilot Dane's Avatar
Group Moderator

Join Date: Mar 2003
Posts: 15,922
NC

12-07-17, 11:52 AM   #9 (permalink)  
With 4" wide joists 8" center to center that's a lot of support and relatively little (4 1/2") unsupported. Durarock isn't structural but it does have strength. If you can stand on one foot between the joists and it feels solid I'd go ahead and tile. Worst case you do get some cracking but it's a small area if you ever have to re-do it. But I think you'll be fine.

 
debeze's Avatar
Member

Join Date: Dec 2012
Posts: 95
CAL

12-07-17, 01:37 PM   #10 (permalink)  
Thanks PD! You have been helpful in the past and I appreciate what you do for me.

My friend (an architect with 35 years' onsite experience) says that rather than using two substances (1. mortar 2. grout), use 1" of cement as the "mortar" surface as a substrate for the tile, and then a single unified product like epoxy grout (money is no object to him) or this adhesive plus grout stuff as both an adhesive plus a grout. That way there's no possibility that the two substances can separate. I guess I am mostly concerned about water getting in there.... but again, it's a small area, with a ton of support, and not a walking surface.

Any further thoughts?

 
czizzi's Avatar
Forum Topic Moderator

Join Date: Jul 2007
Posts: 6,750
VA

12-07-17, 03:57 PM   #11 (permalink)  
Pre-mixed adhesive products are not designed for use in wet areas, which an outdoor area certainly is. Outdoor pressure treated lumber is also subject to lots of expansion and contraction so my thoughts on longevity of your plan are short lived. I understand what you want to do, but not sure on your approach.

 
debeze's Avatar
Member

Join Date: Dec 2012
Posts: 95
CAL

12-07-17, 05:00 PM   #12 (permalink)  
Thanks. Upon reading the fine print, I see it's not recommended for exterior applications. You saved my skin!

So I might go with a thinset mortar and use latex additive instead of water. That's what theguy in the tile store recommended.

What if anything would a water barrier between the cement board and the thinset provide me? Does it have anything to do with the long-term integrity of the thinset? Something else I don't pretend to know that much about the chemistry of mortars with a cement substrate.

 
debeze's Avatar
Member

Join Date: Dec 2012
Posts: 95
CAL

12-07-17, 07:11 PM   #13 (permalink)  
How about Kerapoxy -CQ?

http://www.buildsite.com/pdf/mapei/K...ata-850043.pdf

 
czizzi's Avatar
Forum Topic Moderator

Join Date: Jul 2007
Posts: 6,750
VA

12-08-17, 04:16 AM   #14 (permalink)  
Thoughts running through my head:

-Decks usually take up to 6 months to "dry out" and during that time, there will be a lot of shrinking of lumber. Will this shrinking have and effect on the tiled area?

-Were the screws used to hold the cement board to the joists rated for use with pressure treated lumber? If not, they will rust out.

-Cement boards are usually used for bonding of tile and are not designed to be a structural element. Traditionally they are set in a mortar bed on some other structural subfloor or underlayment. The subfloor & Joist system provides the strength, the cement board provides the bond. The isolation of the two from the joists structure prevents movement from cracking out the tile. The mortar bed is utilized to provide for the uniform support of the cement board to account for any small imperfections in the subfloor.

-Permabase is manufactured with small styrofoam pellets embedded in the cement both to lighten the overall weight of the board, but also allows the product to bend around curved walls. So is it the right product to use in a situation that doesn't have any solid support underneath it.

-While is shouldn't make a difference, it appears the Permabase was installed upside down. There is a different texture on the front side of the boards that I believe helps with adhesion.

-What did you bond (glue) the two layers together with?

-Will the herring bone pattern supply enough lateral stiffness that there will not be any movement n the deck that will effect the tiled area? Don't know how the framing of the deck was installed and if everything is just on hangers will that prevent lateral movement.

-What is the span on the joists and do they meet proper L360 deflection?

These are just some thoughts running through my head. Trying to provide some direction and give you some talking points to continue your research. These are talking points that apply to best practices in a tile installation setting. Yours is a unique situation and normally I would advise against tile on a deck. But given that it is a small area, I want to make it work for you. Thinking that a layer of 3/4" exterior PT plywood as the base would make me feel better with one layer of 1/2" cement backer board set in a 1/4" troweled bed of thinset mortar that is designed both for exterior use and a wood subfloor (some are designed for use over cement slabs only).

The other thought is to go old school and float a mud bed to provide isolation from movement. 3/4" PT exterior plywood, a layer of tar paper on top, wire lath fastened with staples rated for PT lumber and then hand float a 1" mudbed on top using bed mortar. The tar paper creates the isolation from the rest of the deck and the slab would not be subject to lateral movement.

Thanks for giving me a sleepless night to think about this.

 
Marq1's Avatar
Member

Join Date: Sep 2016
Posts: 1,473
MI

12-08-17, 04:38 AM   #15 (permalink)  
The substrate is 2 sheets of PermaBase Durock type cement board, 1/2" thick each

use 1" of cement as the "mortar" surface as a substrate for the tile,

You have 1" of CBU, appears to be well supported. I do not see the need to place another 1" of mud base but if you do do not use regular concrete mix. Mortar contains a higher amount of cement for greater bonding.

Plus you are in CA so the temps/environment are mild compared other locations!

 
Pilot Dane's Avatar
Group Moderator

Join Date: Mar 2003
Posts: 15,922
NC

12-08-17, 05:45 AM   #16 (permalink)  
I would stick the tile down with thinset mortar using latex modifier then grout with a two part epoxy grout. The grout is expensive but one $50 package should be enough to do the job.

You've got 2 layers of PermaBase and you have so much wood structure there is very little gap between your 4x6 joists that I don't think strength will be an issue. The only area I don't know is how you glued the two sheets together. But, even if they delaminate/separate I don't see much problem. The top layer with the tile will move as a unit. And as an absolute worst case it's such a small area that if you do get grout or tile cracking years down the road it's easy to replace and come up with a plan B.

----
5 years ago I took some 1/2" PermaBase and cut into approx 16" squares. I used thinset to mount leftover 3" thick concrete patio pavers to form garden stepping stones. I did not grout between blocks so they are a bit flexible to sit on uneven ground and withstand walking. After 5 years in the weather with no grout or sealing and using thinset for the wrong application all the pavers are still stuck in place and performing well. So, I feel the PermaBase and thinset

 
debeze's Avatar
Member

Join Date: Dec 2012
Posts: 95
CAL

12-08-17, 12:01 PM   #17 (permalink)  
I thought I was the only one spending sleepless nights over this. So sorry! Anyway, thanks for such a long and thoughtful reply. Here is what I can tell you.



-Decks usually take up to 6 months to "dry out" and during that time, there will be a lot of shrinking of lumber. Will this shrinking have and effect on the tiled area?

*** Ihope not. The area is small: 32" X 72". The wood has seasoned for 5 months so far. Fingers crossed.

-Were the screws used to hold the cement board to the joists rated for use with pressure treated lumber? If not, they will rust out.
*** Stainless steel fiber cement screws. I'm covered.


-Cement boards are usually used for bonding of tile and are not designed to be a structural element. Traditionally they are set in a mortar bed on some other structural subfloor or underlayment. The subfloor & Joist system provides the strength, the cement board provides the bond. The isolation of the two from the joists structure prevents movement from cracking out the tile. The mortar bed is utilized to provide for the uniform support of the cement board to account for any small imperfections in the subfloor.
*** Thanks for the lesson. ! I was curious about that. The architect was particular that I should screw only the first layer to the joists.


-Permabase is manufactured with small styrofoam pellets embedded in the cement both to lighten the overall weight of the board, but also allows the product to bend around curved walls. So is it the right product to use in a situation that doesn't have any solid support underneath it.

*** Well, it has four joists running the long way, and these are 4-bys, not the standard 2 by joists. So I have been considering that solid support. Also, they are only 12" oc, instead of the usual 16. So the gaps between them are ~ 8". That's not much space before you hit another joist. I am attching a photo so you can see the support side.



-While is shouldn't make a difference, it appears the Permabase was installed upside down. There is a different texture on the front side of the boards that I believe helps with adhesion.

***, Crap. I I was wondering about that. I read the board for This Side Up and couldn't find anything. Just "Cut this side". 50/50 chance and I'll guess wrong every time. The coated side is up. :>(


-What did you bond (glue) the two layers together with?
*** Mistake here. The sipleFix pre-mixed adhesive + grout. However, I figure it's not exposed to water or extremes of hot or cold (SF Bay area), so I am praying I am ok.

-Will the herring bone pattern supply enough lateral stiffness that there will not be any movement n the deck that will effect the tiled area? Don't know how the framing of the deck was installed and if everything is just on hangers will that prevent lateral movement.

** The deck is 4X6s, spaced12" OC. Span is under 8'. The far side rests on 2 2X12's, and is held down with hurricane ties. On the house side I have a ledger board.



-What is the span on the joists and do they meet proper L360 deflection?
7'10". I meet code, etc.

These are just some thoughts running through my head. Trying to provide some direction and give you some talking points to continue your research. These are talking points that apply to best practices in a tile installation setting. Yours is a unique situation and normally I would advise against tile on a deck. But given that it is a small area, I want to make it work for you. Thinking that a layer of 3/4" exterior PT plywood as the base would make me feel better with one layer of 1/2" cement backer board set in a 1/4" troweled bed of thinset mortar that is designed both for exterior use and a wood subfloor (some are designed for use over cement slabs only).

*** Great ideas. I think that since porceilain, cement, and PT don't rot, the idea was to keep other woods out of the mix.

Hope this helps. THANKS so much for putting so much time into my little mess.

Attached Images
     
 
debeze's Avatar
Member

Join Date: Dec 2012
Posts: 95
CAL

12-08-17, 12:09 PM   #18 (permalink)  
Thanks, PD! Super helpful and clear.

One little question: i have a leftover opened bag of modified thinset from a project 4 years ago. Are you suggesting I buy non-fortified and add liquid latex, or can I get by with my leftovers?

 
debeze's Avatar
Member

Join Date: Dec 2012
Posts: 95
CAL

12-08-17, 12:21 PM   #19 (permalink)  
Re: herrngbone: most of boards are around 50". They are short spans: attached to three joists each. That means they are pinnedmuch more than standard (easy-to-lay!) decking. I'm kinda hoping this little island of tile will be a little island of fireproof stability. Hoping....

 
Pilot Dane's Avatar
Group Moderator

Join Date: Mar 2003
Posts: 15,922
NC

12-08-17, 12:57 PM   #20 (permalink)  
I would be hesitant to use thinset that is that old especially if the bag has been opened. You may find that it has partially cured from moisture in the air.

For my outside stepping stones I used thinset that had a latex additive already in it. All I did was add water and in my case it's held up well. For my other outdoor tiling projects I recall using liquid latex but I can't remember if the thinset already had latex or not. Also, I have seen different flavors of modified thinset with some seeming to have more additives than others. Whichever brand thinset you're going to go with I'd poke around their website and read up on their available products to see which suits your needs best.

 
Search this Thread