Exterior tile installation over living space
This week I got an email about tiling outside over an occupied room. This isn’t something that I’ve talked about so far but this is a high-risk situation and I wanted to expand on it a bit. Here’s the question:
Hello..
I was hoping you could provide some advice. I have lots of experience tiling. I also have successfully installed a wet bed shower. I have a project that I could use your advice on. I have an outdoor balcony that is located directly over a finished room. The existing tile floor is leaking. My guess is the builder cut corners and did not prepare the substraight properly.
The balcony is approximately 18ft by 8ft with a drain in the center. I was going to install a new tile floor in the following manner…
1) install roofing felt
2) nail down galv. wire lathe.
3) apply mortar bed sloped 1/4″ for every foot.
4) apply thin set with membrane on top
5) tile
The is a lot of work for a large area. Do you have any other suggestions? Thank you in advance for your advice.
About two years ago I got to talking with a local representative for one of the major thinset/grout/waterproofing companies in the tile industry. Amongst his duties are product demonstrations, technical questions, and handling problems that their products may be involved in. Typically, the number one problem that they have to respond to is grout issues. Discoloration, mold, efflorescence, etc. This is quite common amongst his competitors also. But as we got to talking, I was quite surprised to hear that this wasn’t the most common issue anymore. It had been replaced by exterior tile installations.
Now keep in mind that I don’t live in Southern California. This is up in the Pacific Northwest. His territory is Washington, Oregon, and Alaska. Also, keep in mind that every tile installation has grout. Not every tile installation is an exterior balcony. In fact, they are really not all that common up here. Yet this was his number one technical issue: exterior tile installations- especially over living space.
The reason that I bring this up is that a lot of contractors don’t take these installations seriously. They don’t think there’s anything more to them than a typical bathroom floor. But there are definitely some things to watch out for with exterior tile installations. Here are a few things that I wanted to talk about:
Waterproofing membranes
Liquid membranes typically aren’t a good idea for this application. But it does matter which product it is. Laticrete, for example, has a great set of instructions for exterior tile installation that involves their Hydroban liquid waterproofing membrane. However, the Hydroban isn’t approved as the primary waterproofing membrane. They don’t specify any of their products to be used as the primary waterproofing membrane.
Your choice in waterproofing membranes is critical. There’s only so many that are approved for exterior tile installations. If it were me, the only membrane that I would consider is Noble Deck by Noble Company. It’s a very thick and tough membrane and it’s made by a company that is a leader in sheet membrane manufacturing. But it needs to be installed properly. Where it ties into the wall is a critical area and needs to be flashed appropriately.
Another option is from Schluter Systems (page 16). They approve their Ditra membrane for exterior tile installation including those over living space. But again, reading the instructions is critical. For instance, they want their Troba drainage mat used as part of the system.
There are other products and methods that will work for the primary waterproofing system. Both products that I mentioned above have really good instructions. They tell you how much to slope the floor, what to install the membranes over, and how the floors should be built. It’s important to do your research before committing to a waterproofing system.
Movement Joints
I haven’t talked about movement joints yet in my blog and probably will at some point. But these are another piece of the puzzle for a successful exterior tile installation. What is a movement joint? Basically, it’s a grout joint in the tile that isn’t filled with grout. Instead, it’s filled with a flexible sealant like caulking. For exterior tile installations, you need either a urethane (best choice) or silicone with shore A hardness. Custom Building Products makes a silicone caulk that meets shore A hardness and comes in colors to match their grouts. The advantage of this is that the silicone joint will be less noticeable if it looks like the grout joints around it.
Where do you put these flexible movement joints? For exterior tile installations, they are to be installed every 8 to 12 feet. So, in the example above, if the exterior balcony is 8 ft. by 18 ft. then you’ll need at least one caulk joint in the middle of the 18 ft. run.
You also need a movement joint around the perimeter of your tile floor. If there is something covering the perimeter then it won’t need to be caulked. If the perimeter joint can be seen then you’ll need to fill it with the same flexible sealant. Typically a movement joint is about 1/4 inch. but can be bigger if you are near the maximum limit of 12 feet.
The One Thing Every Tile Installation Needs: Movement Joints
Thinset mortar selection
Another often overlooked aspect of exterior tile installation is the choice of thinset. For outdoors you’ll need to the strongest and most flexible thinset that you can find. It should meet ANSI 118.15 as a minimum. See my post on the different types of thinset mortar here. Good thinset mortars for these applications are:
Custom Building Products Megalite
Laticrete 254 Platinum
Tile Selection
The best tile selections for exterior tile installations are ones that are impervious. They won’t soak up the moisture. They won’t cause people to slip on them when they get wet. Typically porcelain tiles are best. They need to meet a slippage test called Dynamic Coefficient of Friction (DCOF). For interiors, the minimum is 0.42 DCOF. You’ll want to do better than this number for exterior tile installations. I am not aware of a minimum requirement for exterior tile installation. It’s something to ask about when shopping for tile.
Many people like to shop for slate tile for exteriors. This may seem like an ideal fit. But slate is typically a poor choice for exteriors. It’s porous and the layers will chip off over time. A nice non-slip porcelain tile is a much better choice.
So for exterior tile installations, especially those over occupied living space, the details of installation are critical. With proper research, good installation practices, and good product selections your exterior tile balcony can be counted among the successful installations.
Mike D Genovese says
Hi TileGuy,
I think your article above is very informative.
I am redoing an outdoor porcelain tile balcony in western NC. It’s got a northern exposure but still gets decent amount of sun in late afternoon. We are zone 7 but have seen temperatures down to 5F.
I’ve been researching the various options for the waterproofing of this balcony. I too have heard good things about the Noble Deck membrane. One relatively new product that also looked well engineered is the NAC Extreme Deck Waterproofing System. I’ve looked for reviews on this solution but I’ve had no luck. I was wondering if you have any thoughts/info on this solution. I like the fact it is a double waterproofing solution.
Thanks,
Mike
DIYTileGuy says
I’m not familiar with the NAC waterproofing system but I did take a look at their website and it looks ok. I’ll keep my eyes open for more info about it.
Pete says
We have used noble deck installed by the book and overseen by noble deck reps. The product fails. The drain weep systems are not perfected . Their are breaches in the blue glue seams after less than 3 years past installation. Try explaining that to the million dollar Condominium owners below. Absolutely terrible product and proven a bad choice even after reinstalling twice on 5 different decks. Proof is in the dismantling, what you see when you take everything apart is a disaster. Seams all separated, blue glue deteriorated from water penetration thru the grout and freeze thaw. Think about it…..even after using expansion joints, special thinset, corner patches, everything by the book. This building has suffered from a poor choice using a non proven product starting around 2007.
DIYTileGuy says
That’s unfortunate and I hope that things will be made right by those responsible.
michael a. says
I have a situation with a large red tile deck that directly overlays a living space and a downstairs bathroom. For many years the deck leaked, causing some visible water damage in the living space’s ceiling (wooden slats) and the doorjamb and sheet rock in the bathroom. We had a crew come out and paint the deck with two coats of Behr deck paint and that solved the problem for the last 18 months. However, we know that is not the final solution. Recently the bathroom was re-modeled and breaking through the sheet rock we saw that the 2×4’s were in OK condition in spite of the water. The door jamb was replaced and everything looks fine. We now are ready to address the cause of the leaking and will probably tear up the tile deck and check to see what lies underneath. I surmise that a membrane (if there is one) was installed incorrectly more than 30 years ago. Our hope is that we will not have to replace the ceiling in the occupied room which as I mentioned is wooden slats. We don’t know how much space is between the tile and the ceiling and what was installed in between. Obviously we will need a new membrane and also assurances that the water will drain off the membrane and over the edge of the deck without pooling and eventual leaking. In our situation what would you recommend. We are in the SF Bay Area and get about 20″ of rain each year in the winter season. Thanks
DIYTileGuy says
I like Noble Deck for these types of situations but there are other products also. For example, Schluter has a solution for an outside deck. But this is a tricky installation and the instructions have to be followed exactly. In particular, sloping for drainage, flashing waterproofing up the wall, and movement joints in the tile.
Here’s some information on Noble Deck: http://noblecompany.com/products/noble-deck/
I couldn’t find the Schluter information on their website. It’s possible they don’t have a system for exteriors anymore.
Mark Rippe says
I was hoping to get some thoughts on my exterior tile installation. It’s not over occupied space, but rather a crawl space. I should start by saying that I live in Charleston, SC. The climate here is quite temperate. As I’m fond of saying: “There is no snow, and the only ice is in my glass”. I think this has (or should have) some bearing, as I would hope that my space may not require the same engineering solution as say something in Green Bay, WI, or a Chicago high-rise.
I have a deck that was converted into a covered and screened outdoor space (open on only one side, via screen, to the elements) by the original homeowners nearly 20 years ago. At that time, they also decided to install a tile floor. A plywood underlayment (I’m not sure it was exterior grade or pressure treated) was installed over the 1×6 pressure treated decking, and the tile installed on top of that. Sometime shortly thereafter, I can only assume they decided that they wanted to improve drainage for any rainwater that blew into the space through that screen, so they drilled holes along some of the grout lines. Well, that just introduced water to the plywood underlayment and subfloor. And over the years (almost 20), rot ensued.
I removed the entire tile floor and plywood underlayment. The half furthest from the house came up easily, as the plywood was completely rotted. This was past the point where drain holes were drilled. The half closest to the house was still in great condition. I repaired the damaged subfloor (original 1×6 pressure treated decking) in the half furthest from the house, where some were rotted completed through. No repairs needed in the half closest to the house.
I’d like to restore a tile floor. This may technically be an exterior space (because it is not included in HVAC), but it is roofed and open on only one side to the elements. I have been told that Hardy cement board is not recommended for exterior installations because it delaminates. Why is this? Temperature? Moisture? Both? If I have a solid subfloor (so the tile/grout won’t crack) with an appropriate moisture barrier (such as Schluter filament or Nobel Deck – which I have to research) to prevent any water from getting to the subfloor, and I’m not subject to freezing temperatures or a lot of water from rainfall, why is this not sufficient?
DIYTileGuy says
I don’t know the technical reasons for why Hardibacker isn’t approved for exterior spaces. But most cement boards are. Can you just substitute cement board for Hardibacker and then install a membrane over it?
Jason Forrest says
Hardibacker is fiber board and is not meant to be used as a substrate for decks. We have used permabase or durock when using a hydrostop system that included using their barrier guard with portland cement and fiber mixed in. This system works well under the ditra but we are also building the slope into the truss or deck joist.
DIYTileGuy says
Thank you for this clarification.