After your tub surround has been stripped down to the studs (or the sheetrock, depending on what your tub surround tile removal process left you with), you are ready to prep the space for tiling.This article will take you through the basic process to take your tub surround from studs and exposed insulation to tile-ready.
- Plastic sheeting (6 mil)
- Staple gun
- ½” hardibacker board
- Scoring tool
- Backerboard screws & drill
- Lots of patience
For this tutorial, the tub surround involves one insulated interior wall, one insulated exterior wall, and one non-insulated interior wall (where the plumbing is). We will be installing clear plastic sheeting only on those walls that are insulated.
If your tub surround has a window, before tiling you need to make sure that the wall framing is built up so that the tile falls on the window frame itself. Depending on the width of your hardibacker, you want to make sure that the distance from the wall framing (2x4s) to the inside edge of the window frame is just slightly larger than your hardibacker + mortar + tile, probably between 1/2″ and 1”.
There is a debate that exists between the necessity (or wisdom) of installing plastic sheeting, also known as vapor guard in this instance, behind backerboard if one is also using a waterproofing agent such as Redgard on top of the backerboard. Feel free to do your own research on this; I have done so and have decided plastic sheeting over insulation is a good idea. Use a thickish sheeting, such as 6 mil.
Measure the first wall width.
Add 6”-10” to that wall width, then cut your plastic sheeting. When unfolded, it will be 10’ long.
Staple a top corner of the sheeting. If your backerboard will be adjacent to and flush with the drywall, line the edge of the plastic up with the drywall, and staple it evenly down that stud. Do not leave overlapping vapor barrier in this instance.
Smooth the sheeting flat, and staple the other top corner.
You should have some overlap at the corner. Aim for 4”-6” of overlap.
Tuck the bottom of the sheeting behind the tub itself. (Trim the plastic prior to doing this if necessary.)
You want the vapor barrier between the tub and the insulation.
Keep vapor barrier flat, but don’t worry so much about pulling it completely taut.
Work the staples down the sheeting, stapling every foot or so.
Around the window frame or recessed shower shelf or any non-flat deviation from your wall, cut your vapor barrier slightly larger than the true fit. Staple the plastic to flat surfaces of the wall frame, then cut a diagonal slit to the corner (but not further than the corner).
Pull each flap of the triangle gently down and staple into place.
When it comes to covering the window frame, your vapor barrier should be cut wide enough that it will wrap around the wall framing with an inch or two of excess.
Use the ends of a pair of scissors, or a screwdriver, or whatever flat tool you have available to push the excess vapor barrier into the gap between the window frame and wall framing.
Cover all insulated walls with plastic sheeting, remembering to cut wide enough for overlapping on all edges. If there are any staples that didn’t quite “take” (as in, they stick out enough that the backerboard might not lie flat), hammer those down carefully. You’re now ready to tackle your cement backerboard, also known as hardibacker, duraroc, or others.
You’ll want to install backerboard in as few, and as large, of sheets possible. So begin by measuring one of the walls where the largest backerboard piece will go, then mark your board. Note: It is much easier to cut backerboard when the two sides are large-ish. It’s much harder to trim off, say, an inch than it is to break off a foot. Keep this in mind when mapping out your hardibacker layout.
Take a backerboard scoring tool (available for sale at your local hardware store) in hand.
Hold the metal ruler or square in place as you score firmly along the line. You need to cut with intention, but don’t feel like you must muscle your way through the backerboard during this one step.
This was a hard cut, as I only had to remove about an inch. Lay down an old 2×4, or something that provides an elevated straight edge. Place your backerboard on top of the 2×4 with the scored line directly above the edge of the 2×4. Apply pressure (jump, if you have to) to both sides of the scored line, and your backerboard will break along the line. However, this doesn’t work when one of your sides is very small, as is the case here, because there’s little leverage. I recommend scoring both sides of the backerboard in this case and using a hammer to pound off the small edge.
If some of your cuts involve corners, or more than just a straight line, you may need to get creative in how you pull off the cuts. But the basics stay the same: score the backerboard, place the score line directly on the edge of a 2×4 or other elevated straight edge, and figure out some way to carefully apply pressure equally to both sides of the score line. This cut involved a right angle, so I was precise in my scoring and kept the pressure points away from the scored corners while breaking the hardibacker.
I used a hammer and chisel in the very corners so the back side of the hardibacker wouldn’t rip or tear away.
Dry fit your backerboard onto the wall of your tub surround to ensure a great fit. Begin screwing it in if it fits well.
If for some reason you need to shave some off any bits from the sides to make it fit better, I recommend a drywall saw or a hammer and chisel, with the chisel’s edge working along the side of the hardibacker rather than the front or back.
Use your backerboard screws to install the hardibacker.
Screw the hardibacker into the wall studs to ensure proper support. This is why, during our tile and drywall removal process, we cut the drywall halfway down a stud – so the sides of the hardibacker would have somewhere to attach to.
You want to put in enough screws that the hardibacker is sufficiently supported, but you don’t have to get crazy about it. Do attach the board to every stud at least once, though.
It’s important to mark where the studs are if you won’t be able to see them once the hardibacker is in place. (An example of this is under a window.) This stud and others were marked on the windowsill.
Keep edges as flush as possible. Remember, the goal here is not just to cover the insulation, but also to provide a continuous, flat surface on which to tile your shower/tub surround successfully.
If you haven’t already, smooth out any surfaces that will be adjacent to your backerboard. This includes the ceiling or connecting walls.
Not shown: For the windowsill, I used ¼” hardibacker to frame the four sides of the window, because the ½” board would’ve been too thick when tile was placed. Feel free to make adjustments like this as needed to suit your space. But use the same size of board for all the walls, for continuity and proper moisture protection.
Continue measuring, scoring, cutting, and attaching your backerboard until it’s complete.
In the instance of cutting holes in the middle of a larger piece of backerboard (for your tub faucet, mixing valve, and shower head, for example), you’ll want to measure carefully where the hole needs to be.
Mark the size of the hole. For the tub faucet pipe, a small 1” hole will suffice.
For the larger mixing valve, a larger hole is needed. Find an object of the same size and trace around it. (A funnel works perfectly for this, because you can mark the very center of your circle, then peer through the funnel hole to make sure your traced circle is centered.)
Score an X (or a star-like X, with lots of lines from the middle point to the perimeter) in the center of your hole, with the ends of the X touching the hole’s perimeter. Score the perimeter.
Hammer, chisel, or hammer-and-chisel your hole out.
Scrape or cut the sides of the hole clean, then dry fit the backerboard to the wall. If you’re in position, measure, mark, and chisel any other holes you might need in that piece before attaching it.
When the hardibacker has all been installed, it’s time to apply Redgard. Redgard is the water sealing agent, or moisture protection deputy, for all the seams, cracks, and edges that have occurred during your tub surround prep. It’s like paint, but much thicker and gooier.
The key here is to hit every space where the hardibacker’s face has been punctured or sides are exposed. This includes screw holes, seams, and even edges.
In the case where your seams may not line up exactly perfectly (we’re not professionals, after all), use Redgard to fill in the space.
Wipe a bunch onto your paintbrush, then brush perpendicular to the seam or hole needing to be filled. The goal is to create as water-tight a tub surround as possible.
I recommend using Redgard at the ceiling, around the window seams, around the tub, and every other joint. It’ll be pink when you brush it on, but as it dries, the substance will turn a bright cherry red.
Apply it in the small gap between the backerboard’s and the window frame itself. Wipe off excess that gets onto the window frame, tub, or anywhere else – it’s much easier to remove when wet, and this stuff dries pretty quickly.
Apply Redgard around the cut holes for plumbing. Be sure to get the stuff to cover and coat the inside edges of the hardibacker, if at all possible.
Fill in small and large spaces at corners with Redgard.
With your plastic sheeting, hardibacker, and redgard all installed and applied, you have completed preparing your tub surround to be tiled. Congratulations! Now comes the fun part: laying the tile tub surround of your dreams.