How to Install a Marble Tile Tub Surround

This project was typical with a twist. It’s very common to upgrade a bath renovation with a new tub, tub surround tile, floor tile, etc. It’s less common to also add a window or replace every bit of drywall. But, if you’re already going mostly to the studs on a renovation project anyway, then it’s usually only an added incremental cost to go ahead and add every upgrade you want. Read on for tips on how to correctly install a marble tile tub surround!

The Before

There was plenty of upgrade potential on this project. The house was built in the early 1980s, and the original bathroom definitely showed its age.

The tub surround was made of dull brown cultured marble. This is a great material for waterproofing, but not so great for aesthetics. And the tub itself was just plain old. Steel tubs start rusting immediately when the porcelain layer gets scratched, and this particular tub was also leaking around the drain:

And finally, the bathroom was dark and stark with no natural light at all. This renovation would fix all of these problems.

The Plan

Demolishing original cultured marble tub surrounds and steel tubs is generally a surprisingly easy demo process. For this project, taking out the drywall and floor tile would actually prove to be the most difficult and messy step.

The full to-do list for this project:

Demo tub and surround
Chisel up floor tile and thinset
Rip out original vanity, toilet, and textured drywall to the studs
Reconfigure exterior wall for new window install
Re-plumb for new fixtures and install new tub
Install concrete backerboard with RedGard waterproofing
Install new tile for tub surround and bathroom floor
Install new drywall with finish taping/seaming and painting
Install new vent fan, new lighting, and new vanity

Did all go according to plan? Read on to find out!

The Demo

Ripping out an original 1980s -vintage tub surround usually reveals a moldy dryrot mess, since almost all homebuilders of that era saw nothing wrong with tub tile installed directly on drywall. But in this case there was no moisture intrusion at all, since (unlike grout and tile) cultured marble is actually waterproof — and also easy to demo with a small hand sledge:

Removing the bathroom floor tile was more difficult, since the previous installer had gotten pretty good thinset coverage between the tile and the concrete slab foundation. Since the room was a bit too small for maneuvering around a pneumatic hammer, the tile and thinset bits had to be removed the old fashioned way with a hammer and cold chisel.

Removing the old steel tub was the easiest part. Chopping it into manageable bits with a sawsall makes haul away easy. And, ripping out the tub revealed plenty of room to reconfigure the drain plumbing for installing a replacement:

Removing the drywall was actually the most tediously annoying demo step. The bathroom was originally built with a requisite ceiling soffit above the vanity lighting that, when removed, let loose a cascade of loose-blown insulation from the attic above. And the heavily textured original wall drywall had to be ripped out small piece by piece since the 5ftx8ft room dimensions and 22-in doorway opening didn’t lend itself to peeling off and hauling away large sheets.

The Carpentry

Once everything was ripped to the studs, re-framing the exterior wall for a new window was very straightforward. Normally, you’d want to avoid putting a window in your tiled tub surround if there’s any other exterior wall to work with. But with this house layout it was the only option for letting in some much needed natural light.

So if you do need to put a window in a shower or tub wet area, here are some tips. First, be sure to use a vinyl window. Vinyl is waterproof and won’t absorb moisture or change dimensions with wide temperature swings. Second, put the window opening above (or at least mostly above) where the water will mostly spray.

And third, be sure to properly flash and seal the exterior window trim. You don’t want to forget that moisture will get in through an improperly waterproofed window install from the outside too!

Since the new window opening in the new tub surround would be too high up on the wall to conveniently use for shelf storage, the clients also got a nice wide inset niche framed out below the window for storing soaps and shampoos and whatnot. Here’s how the project looked once the carpentry was finished and ready for tub/backerboard install:

The Waterproofing

The minimum code compliance for a tile tub surround install is just a vapor barrier (sheet of plastic) and concrete backerboard. But if you want to ensure a nice dry showering experience that’ll last a lifetime, spend an extra $100 for RedGard or similar paint-on waterproofing:

Remember that tile and grout aren’t waterproof. And while concrete backerboard is water resistant, it’s not waterproof either. Putting a continuous layer of waterproofing directly underneath the surface tile layer ensures that a shower or tub surround will dry out very quickly between uses. This in turn ensures a maintenance-free mold-proof happy bath future!

Be sure to pay special attention to waterproofing inset niche spaces and of course windows and other openings in the tile wet areas. For sealing seams in the backerboard before waterproofing, inexpensive masonry sealant like Silka works just as well (and is quicker to apply) as conventional aluminum mesh tape and thinset:

Now that the whole enclosure is waterproofed, the surface tile layer will simply be decorative.

The Tub Surround Install

Speaking of decorative, the 3×6-in polished marble tiles chosen by the client definitely needed good waterproofing. Marble is a natural stone that will absorb quite a bit of moisture even through a polished surface. It’s also a semi-transparent stone, so installation required the right thinset choice. And finally, natural marble is a naturally variegated stone — different tiles have naturally different shadings and grain. The bottom line? When installing marble tiles, pay attention to a few tips if you don’t want your final result to kinda suck.

Tip #1: Waterproof that Substrate!

Even ceramic or porcelain tile and grout aren’t completely waterproof, so this is a general guideline for any shower or tub surround install. But it’s very important for a shower or tub surround with natural stone tile. If the marble tile doesn’t quickly dry out between uses, then the trapped moisture will encourage mold growth between and behind the tiles. Eventually, mold can penetrate into veins and cracks in the stone tile and then be impossible to fully clean.

But if you just put a good waterproofing layer immediately behind the surface tile, then the moisture that’s absorbed by the tile and grout will evaporate back out very quickly between uses. Any mold cleaning maintenance will just be of the everyday simple getting rid of surface soap scum and whatnot kind. Easy-peasy!

Tip #2: Use the Correct Thinset!

Marble tile is both semitransparent and moisture absorbent. This can mean really bad news if you use cheap grey thinset for an install. First, the grey thinset layer color will significantly darken even thick-ish marble tile and make it appear noticeably dull and lifeless. And second, the lower-quality grey portland cement mix in lower-cost grey thinset can react chemically with the minerals in natural marble resulting in scaling, discoloration, or other unpredictable results.

The general rule of thumb? It’s best to treat any kinda-transparent tile install as though it were glass tile and use the same care with choosing an appropriate high quality natural stone or fine porcelain thinset for the job. Or at least use quality white mortar to help avoid unexpected tile dulling or discoloration.

For projects like this, I’m a big fan of Custom Building Products’ “ProLite” Mortar. It’s a highly modified thinset mortar that’s truly way less dense than traditional mortar. A 30-lb bag will indeed give the same coverage as a 50-lb bag of traditional modified mortar, and it mixes to a nice buttery consistency that’s really easy to work for wall tile install applications.

Tip #3: Do NOT Randomize the Tile!

Speaking of thumbs, it’s a general rule when installing any tile to completely randomize the tiles by opening and grabbing from multiple boxes as you go. Since each box of natural stone tile likely came from a different part of the quarry (or completely different quarries), randomizing your install this way will usually prevent unsightly transitions in the finished result. No one likes to see an obvious seam showing precisely where one batch of tile ended and another began.

That linked example is pretty extreme. In general, you usually just want to make sure that any supposedly random pattern tile (either natural stone or engineered pseudo-natural ceramic) actually looks random after the actual install is done.

But in this case the clients chose discount marble tile from Floor&Decor, which meant that there was A LOT of variation in tile color, hue, and visual texture between boxes. Completely randomizing the tile install would likely have resulted in some pretty jarring transitions between individual tiles placed next to each other.

So, when you’ve got a natural tile install situation like that, the best approach is to take some planning care to install the tile in a semi-random manner. In this case, some of the tile batches were dark and full of natural veins while others were very white and almost quartz-like in appearance. So, it made sense to install the darkest tiles at the bottom of the tub surround and transition to lighter tiles nearest to the window and ceiling and outer perimeter:

I still included a few patches of darker tile higher up on the walls, but tried to minimize instances where very light tiles were right next to very dark tiles by making wider patches of light/dark tiles. When complete randomization won’t work, using a bit of thematic direction for your semi-random install often can.

Tip #4: DO Use a Quality 10-in Tile Saw!

The clients were very keen on an install pattern that didn’t show any tile edges around the perimeter of the niche and window insets. Despite lots of advance planning and measuring, it wasn’t possible to get the wall framing precisely right to make this happen. The result was wall framing that was 1/4-in off from non-edge showing bliss:

So, what do do short of tearing everything apart and starting again from scratch? Fix it in post.

Marble is a very soft material, so in theory it can be cut or ground to nice thin slivers if you start with a solid tile that doesn’t have many fractures or veins. I took full advantage of this quality for grinding fill tiles to complete the window and niche openings:

Yay quality equipment!

The Floor Tile Install

The clients chose a large-format natural marble tile with an elongated hexagonal shape. The tile had a completely square edge profile, so a level install was an absolute must to prevent stubbed-toe uneven-ness.

The solution? LevelQuick! This is a no-brainer for tricky tile installs on an uneven concrete slab foundation. Just two bags mixed to thin pancake batter consistency was plenty enough to level the whole substrate:

The result was a dead-flat marble tile install that’d be guaranteed to not hurt the feets.

The Fan and Lighting Install

There was a 1980s -vintage combo exhaust fan and heat lamp combo kit installed in the bathroom ceiling originally, but like most builder-grade original installs it was a bit suspect. There was no actual roof or soffit penetration anywhere near the fan to indicate that it was actually properly ducted to the outside, and holding a piece of toilet paper up to the fan showed that the airflow was indeed going nowhere.

Demo validated this suspicion. The builder had not only not ducted the fan at all, but loose fill attic insulation was packed tight all around the fan housing. It was literally blowing moisture to nowhere.

So, the proper fix was to install a new fan along with ductwork connected to an exhaust hole cut into the nearest exterior attic wall soffit.

Using plastic sheeting to keep the attic insulation in place and metal duct tape to air seal the fan housing install looked like this:

Since the exhaust fan install required cutting into the ceiling to run new wiring anyway, it was an easy added task to add some additional overhead lighting to the tub area. The clients found these LED direct mount light kits at Home Depot, which were perfect. IC rated for direct contact with attic insulation, wet rated for shower areas, and even dimmer switch compatible and adjustable for color hue.

Now time for the finish bits!

Drywall, Grout, Trim, and Paint

The clients chose a neutral off-white “snow white” grout color to complement the marble tile, and long thin stone trim bits to cap the open sides of the tub surround tile:

Pro tip: never use sanded grout for marble tile. The abrasive grit will scratch and dull the polished stone tile surface. Instead just plan ahead to ensure that all the grout lines will be 1/8-in and use unsanded grout for all surfaces.

Another pro tip: use sanded color-matched caulk for all tub/tile seams. Even a well-mounted acrylic tub will flex a bit with each use, so packing the inside tub/tile seam with grout will fail over time as the joint flexes. Instead, simply use the color-matched caulk that PolyBlend and Mapei sell. Sanded caulk works best at holding up to future scrubbing and cleanings.

The bathroom also got all-new drywall from floor to ceiling with just a very light plaster texture:

Add new baseboard and doorway trim with a new Ikea vanity and sink, and every wall and surface of the new bathroom got an upgrade.

Before vs After Comparison!

Before renovating, the original 1982 bathroom had all the charm of a builder-grade Motel 6 right down to the brown cultured marble and nonworking heat lamp and fan combo: