Folks sometimes get hung up on waterproofing when thinking about shower niches. I think this results from thinking of a shower niche as a big ‘ol hole in otherwise waterproof field tile. But here’s the thing. Tile and grout aren’t waterproof to begin with. A shower niche opening is just a continuous part of all the rest of the wall area that needs to be waterproofed for a proper wet area tile install. This post describes how to easily (and permanently) waterproof a shower niche opening in your custom tile shower or tub surround.

Why you need to waterproof UNDER the tile

Here are two facts of life. Tile is not waterproof, and grout is not waterproof. The tile surface of a shower or tub surround is just a finish layer. It makes a bathing space attractive and (hopefully) easy to keep clean. But tile and grout alone DO NOT waterproof a space.

For example, here is what eventually happens when you install tile and grout on a tub surround wall with no waterproofing underneath.

It usually takes 5-10 years for a tile and grout install on drywall to start showing obvious surface problems from fungus and mold in the wall framing. But tile on bare concrete backerboard with no waterproofing will also result in an increasingly musty smell and increasingly difficult to clean mildew problem long before the install gets to voting age.

This is why tile shower and tub surround installations need a continuous waterproofing layer underneath all the wet area surface tile. Just using concrete backerboard isn’t enough, since concrete backerboard is also not waterproof. You need to budget for an extra day of labor and a $50-$150 triple coat application of RedGard or equivalent elastomeric waterproofing. This will guarantee your shower or tub surround tile installation for a lifetime.

This is also why waterproofing a shower niche is no different than waterproofing all the rest of a shower wall.

An inset niche is not a hole in otherwise waterproof shower or tub surround field tile. It is just part of the wet area wall that needs waterproofing underneath the surface just like all the rest.

Why preformed niche inserts suck

This is pretty clear once you get over the idea that a shower niche needs some sort of extra special leakproofing. A premade shower niche insert will not give the flexibility of a truly custom shower niche. You can’t maximize usability and perfectly match the wall tile layout with a prefab insert.

Any custom tile shower or tub surround remodel requires going to the studs to begin with. So ditch the prefab junk and go custom instead!

A truly custom framed and waterproof niche space will perfectly match the ideal size/design requirements for your specific shower or tub surround tile install. And prefab shower niche inserts are also a pain to work with anyway. It’s actually easier (and therefore faster and cheaper) to simply frame an ideally sized niche opening and then just finish it out like all the rest of the wet area wall. Here is a detailed step by step walkthrough.

How to make a custom waterproof shower niche

Working flexibly with the wall framing can get you the most usable niche space possible. Much like closet space, I’ve never met anyone who’s complained about too much shower storage. So you’ll first want to figure out how to rejigger the existing wall to get a big opening.

step one: frame it big!

You want to go large on niche space framing at the outset. Framing the inset space larger than the finished and tiled opening will give you flexibility to make the niche opening perfectly match the field tile layout and pattern. Also, everyone likes a nice big niche for storage!

You can always make a waterproofed niche space smaller on the fly by putting in some scrap tile shims to make it perfectly match the wall tile pattern dimensions. You can’t, however, make a niche space larger once it’s been framed, wrapped in backerboard, and waterproofed.

step two: Make it deep!

Inset shower or tub surround niche spaces are generally 3-1/2 inches deep, because that’s the depth of a 2×4 framed wall. However you can get an extra 1/4-in of depth by using quarter inch backerboard for the back of the niche. Remember that an inset wall niche buts up against the drywall or plywood surface of the opposite wall.

So you don’t need an extra rigid 1/2-in thick piece of concrete backerboard to support the tile that’ll go in the back of the niche. Just use polyurethane construction adhesive or 100% silicone to glue 1/4-in thick backerboard to the back of the drywall. This will provide plenty of support for the tile that will go on the back of the inset niche.

The pieces of concrete backerboard you’ll install along the sides, bottom, and top of the niche opening will also hold the backerboard in back of the niche in place. PRO TIP: You don’t have to use extra expensive stainless steel screws to install concrete backerboard. Regular exterior coated deck screws will work just fine. Just DO NOT use drywall screws!

And you don’t have to make all these bits of concrete backerboard fit together exactly perfectly. But, getting a good fit with tight seams will make the next step easier and faster.

step three: fill the seams!

This is a really key step to properly waterproofing a shower niche insert. You can’t leave gaps for moisture to wick through. The traditional method is to use fiberglass mesh tape and thinset to fill concrete backerboard seams.

But this method is a real pain especially for sealing outside corners and the seams inside an inset niche. The good news? You don’t have to use old-school mesh tape and thinset. Instead you can simply use Sika masonry sealant to close up all the backerboard seams and gaps.

Just be sure to use thick disposable latex gloves when you smooth it into the concrete backerboard seams. Heavy duty polyurethane sealant is like superglue when it gets on your skin. PRO TIP: Sika masonry sealant is the same thing as (3x more expensive) “Kerdi-Fix” joint sealer sold by Schluter Systems for installing their Kerdi waterproofing membrane. So don’t let an installer talk you into using super expensive stuff for sealing backerboard seams. Plain jane masonry sealant does the job just as well.

step four: use plenty of waterproofer!

This is the most important step for a waterproof shower niche. Simply use two or three good thick coats of a quality liquid waterproofing membrane. The best in my opinion is RedGard (also there’s a Home Depot with coupons just down the street from my house, so it’s where most of my reno shopping gets done). If you’re closer to a Lowes, then Mapei’s “Aquadefense” is also popular. Either one will work just fine so long as you take the time to apply several thick coats.

You need multiple coats because the paint-on waterproofer will shrink a bit as it dries and hardens. This can cause cracks and pinhole openings in a thin coat. So, roll it on nice and thick. Then wait an hour for it to dry, and put on a second thick coat. Then apply a third coat to your inset niche for peace of mind. Use a cheap chip brush to get the RedGard into all the inside seams with each coat.

Putting a continuous waterproofing layer on top of the concrete backerboard is the key to make any tile shower or tub surround install last a literal lifetime. Niche or not, it is the best practice for waterproofing a custom tile shower or tub surround project.

This is why waterproofing a niche is no different than waterproofing any tiled wall in a shower or tub surround. It just requires paying more attention to closing up all the extra seams and applying an extra paint-on layer for good measure.

Step five: Slope the niche bottom!

This is a very important finishing step. Even a properly waterproofed shower niche will be a real pain to keep clean if it collects standing water all along the niche bottom. So be sure that your installer tilts the finish tile in the bottom of the niche to drain properly.

I always suggest an agressive 1/4-in or more per foot slope for a niche bottom. It’ll make your shampoo bottles sit at a bit of a tilt. But it’ll also shed water super quickly. This’ll keep the niche bottom completely dry between uses.

More shower niche tips

You can find lots more info and advice for shower niche design in this post. But here’s the bottom line. Truly custom and maximally usable shower and tub surround niche inserts should be large as possible and also sized to match the field tile layout and pattern. This is why prefab niche inserts suck. They’re arbitrarily sized. They’re also completely unecessary so long as your installer does their job to ensure a truly waterproofed install for all of the wet area tile.

So this is the simple way to waterproof a shower niche. Just properly waterproof your tiled shower walls!