Waterproofing penetrations in tile installations

by Roger

When you build a shower you will eventually need to make some holes in it – it’s just part of the overall process. You’ll need to install frames or hinges for your shower doors, grab bars, shower curtain rods, a picture of your pet iguana – whatever. The problem is that now you have that completely waterproof shower you really don’t want to go poking holes into the waterproofing.

No matter which waterproofing method you’ve used any fastener penetrations will have to punch a hole into it. You want to make sure you install your screws properly in order to maintain the integrity of the waterproofing. You don’t want to ruin all your hard work because you need to drive a screw through it!

The first thing you need to do is mark the exact locations of your screw holes. Most things like grab bars come with little templates you can hold up and get exact placement. With shower door frames and stuff like that you can hold up the frame piece and mark the correct location.

Ideally you want to have the placement of things like grab bars in mind before you even put the substrate up on the wall. This way you can instal backing for them. A 2×6 between the studs in the right location eliminates the need to use wall anchors and gives you a solid framing piece to screw directly into. That isn’t always possible (things are added later, layouts change, etc.) but if you can do it you will save a lot of time.

Spade drill bit for tileOnce you have the location of the holes marked you need to take your drill and put a hole there – all the way through the substrate. I normally use the spade-shaped bits for most tile and stone. They look like the little arrow bits and are normally labeled for use with glass tile, they work with nearly any tile. Make sure you get the correct size for either your screw, if you have backing, or your anchor if you don’t. They look like this:

You want to drill slowly! If you attempt to drill too quickly you may burn up the bit and/or crack the tile. That sucks – just trust me on that one. It’s usually easier if you have a spray bottle with water and mist it down as you drill through the tile, it helps keep the bit cooled down.

Holes drilled for screws It’s also much easier to drill through grout lines if you can. That doesn’t always lay out correctly, but it helps tremendously if you’re able to do it.

For this particular post I’ll be using a small two foot grab bar installed on a shower wall. You can click on any of the horrible photos to see a full-size version.

Once you get the holes drilled through in the correct location get some 100% silicone and fill each hole all the way up to the surface. This particular grab bar has a total of six screws – three on each end.

penetrations filled with siliconeOnce the holes are filled with silicone push your wall anchors all the way in. Silicone will ooze out as you do this, it should – it means you have a full hole and there is enough silicone to seal whatever you place in there.

The little red things are the screw anchors I’m using. If you have solid backing behind your screw locations you can just skip this step – you know – since you aren’t using screw anchors.

If you do have backing and aren’t using anchors you need to ensure that you have screws long enough to penetrate through the tile, through the substrate and into the blocking you placed back there. 2″ or 2 1/2″ screws are normally what you want.Screw anchors placed in holes

When you have your holes filled with silicone, and your wall anchors in if you’re using them, go ahead and install your grab bar or whatever is causing you to drill holes into your brand new tile.

As you drive the screw in the silicone will seal the penetration. No matter which waterproofing method you’ve used, the hole will be sealed all the way from the surface of the tile to the area behind the tile substrate.

 

 

Waterproof grab bar installed

And there you have it. Completely waterproof fastener penetrations in your brand new tile. As long as you fill those holes with silicone you will never have problems with leaking or any other issues that commonly derive from poking a hole in your waterproof wall.

Besides, if you’re hanging a picture of your pet iguana in your shower you already have bigger problems to deal with…

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Tom

Hi Roger,
Once again your site popped up on the Google with the info I needed. ..and more….

For the pet iguana pic, should I go with 11×14,or try and find one of those custom print houses that could wrap the entire shower with a pic of my iguana? Maybe graphic wrap could be waterproof too! It could be the new thing, thanks for the idea!

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Rick

Hello Roger,

I am planning on installing a fold-down seat on the wall opposite the ‘wet’ wall (where the shower fixtures are located). This fold-down seat was in the plans from the beginning of this shower project so I reinforced the wall area with two 2x4s going horizontally between the studs. The seat is made for showers. I have 1/2 inch hardibaker substrate and then 12×12 wall tiles. The brackets for the seats (left and right sides) take 4 screws each. Three screws in the top of each bracket that span a total distance of 3 inches and one screw in the bottom of each bracket approximately 3 inches below the center screw in each bracket. It is a fold down seat with no supporting legs. It is only supported by the brackets. My question is – when I install this seat, is there a potential for the brackets and screws to place too much force (torsion) to the tile on the wall and possibly pull the tile away from the wall or possibly crack the tile?

Thanks for your help.

Rick

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Roger

Hi Rick,

Provided you hit the studs you placed into the wall, and they are fastened securely, it shouldn’t have any problems at all.

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Charles

Hello Roger,

For a tub surround redo, what do technique/products do you recommend to clean up the bathtub surface (remove old caulk and dirt) before installing hardibacker and caulking it to the tub? I am going to put Hydroban on the hardibacker. I was thinking of using a razor blade for the caulk and a Scotchbrite pad with Simple Green for the rest. Does the surface have to be perfectly clean, or is it ok to have some tiny rough spots here and there?

Also, I installed hardibacker on two short walls which are at 90 degrees and will be subway tiled (the cooking range goes against these walls). Before I found your site, all joints were taped with thinset, including the corner and Redguard was painted on the seams (with mesh in the corner seam).

The wall will have subway tile. To follow your recommendation to not thinset vertical corners,I was thinking of making a cut down the corner, running a caulk bead, and then reapplying Redguard with mesh to allow for independent movement. Is it worth the effort for a “range surround”? The only water the wall would get would be a spill or maybe steam from cooking.

Thank you.

Charles

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Roger

Hi Charles,

Razor blade and scotchbrite will work fine. A few rough spots are no big deal. I would leave the corner as it is, it’ll be fine with a range surround.

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Karin

Roger-

Just checking that this is the waterproofing concept I would use when installing a slide bar over the Schulter-KERDI membrane?

Thanks,

Karin

Reply

Roger

Hi Karin,

Yes it is.

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Randy

Super site/info! I wondered about penetrations messing with the nice waterproofing- good read. Q: I will be making my shower curb out of concrete/brick blocks as mine is on top of basement concrete floor…this site convinced me of this verus wood 2x4s. So…..when I install my shower door on top of my concrete curb….how do I screw/fasten the door fasteners into/onto the curb??? I will be using 2 layers of approx 2″ brick plus thin layer of thinset over this so I can stick the kerdi membrane over it then tile over the curb. Now when the shower door instructions call for screwing a few door brackets into the curb (sliding door) what do I use (tapcon screws?? Do I predrill the screws using masonry bit first?). Do I need a 2×4 on top to hold the screws or is solid concrete and tile the way to go…..I only want about a 4.5-5 ” curb height and I intend on backsloping the curb by 3/8″ for drainage when I tile it… help appreciated!!!!!

Reply

Roger

Hi Randy,

Never saw a shower door call for that. Normally the bottom rail is siliconed to the tile and the two side rails are set on top of the ends to hold it in place. Are you sure that’s what it calls for (you already have the doors)? Or is it just assuming it’s attached in that manner?

You can use tapcons by drilling, filling with silicone, then installing if that’s what you need to do, but I highly recommend against drilling into a curb for ANY reason.

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Larry

Hello,

wanted to ask a quick question. But first a history, this is my second tile job, the first was the downstairs half bath, turned into full bath with steam/shower, learned a lot, pony walls, neo-angle, etc. which included all kinds of life learning experiences after being ripped off by the (so called) contractor, if I had only used the baseball bat on his ass! Anywho, I am doing the second floor hall bath, removed iron tub, installed whirlpool tub, reduced the size to add to the extremely small master bath. At the moment I am doing the tile, this is when I found your site because of niches, (just so you I had done some things wrong and some a lot better then the steam/shower). Now to the question, I had to remove a couple of tile after they had been in place for a day, due to miscalculating measurements (spacers). In do so, I damaged the Redgard. What is your recommendation in repairing? I was going to use fibertape and mortar, allow to dry then reapply the Redgard in the damaged area. So in stead of jacking it up, thought I ask you.

thanks

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Roger

Hi Larry,

That’s exactly the correct way to repair it.

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Ramon

Roger,
I am doing a job that as of now will be two bathroom floors over well aged concrete. The homeowner wants heating mats and the new Ditra system is about 3x any other mat so I am using “another” but still want to use Ditra under the tile…I know that the heat mat must be encapsulated..Under or over the Ditra? Please suggest a BRAND name thinset suitable to 1.)Encapsulate the heat mat. 2.) bond the Ditra to the concrete and 3.) Bond the tile to the Ditra. I am very confused about the thinset requirements. Thanks so much..Ramon

Reply

Roger

Hi Ramon,

You need unmodified thinset for everything in that installation. If you read through my post on unmodified thinsets it will give you the rundown of all the most commonly available.

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Ann

Dear Roger,

We are doing our umpteenth tile installation. Or, at least it seems that way. Our oldest son was over last night, and, as usual, was giving advice to us on what we are doing WRONG on our tile installation plans. Since there is at least a small chance he is correct, I thought I’d ask your opinion.

We are planning to put 21″ x 21″ tiles in our basement bathroom floor. They are very high quality, textured-type commercial tiles. He stated that tiles installed on concrete will always, always crack, and that we should go with smaller tiles to prevent this. (He worked at one time for a “high-end” remodeler, so he has some experience in these matters.)

Our first thought is that if the tiles are installed correctly, with actual thin-set under the entire tile, it shouldn’t crack. But, what do we know? We’re just the old, feeble-minded parents. Should we play it safe and put Ditra over the concrete and under the tile? Go with smaller tiles? Give up and use carpeting?

We couldn’t have done the tile projects we’ve already finished without you….many thanks! We have already purchased your Design, Tile Tips, and Shower/Tubs manual, and are rereading them several times before proceeding with the basement bathroom remodel – then we’ll tackle the upstairs with the Kerdi shower kit, so we’ll order that book at that time. You have done everyone a favor by writing all this stuff down!
Ann

Reply

Roger

Hi Ann,

He is partially correct. Concrete ALWAYS cracks – always. If tile is bonded directly to the concrete it will crack as well, in the same spot. It does the same with smaller tiles, except it will normally only give out at the grout line, since it is the weak point and there are a hell of a lot more of them. A crack isolation membrane of some sort is best, be it ditra, redgard or whatever.

Concrete also is manufactured to crack in specific areas, the expansion or saw joints. You need soft joints over these, whether the membrane is there or not. This compensates for the controlled crack.

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Freeman

Roger,

I am in the process of installing the backerboard surround for my new shower and am going with the liquid redgard method for waterproofing but am stumped with one issue. The water fixture has a 3″x5″ plastic plaster guard that is supposed to be installed flush with the interior finished wall. The plaster guard has a number of holes for the attaching screws and water flow adjusting screws. My question is how do you seal this type of penetration? I realize that the escutcheon has a rubber seal that will surround the opening but water will still be able to follow the grout lines and penetrate the opening.

Reply

Roger

Hi Freeman,

The water running down the grout lines is stopped by the foam on the back of the escutcheon. For the rest of the waterproofing of that hole, you do it like this.

Reply

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