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DIY Bathroom Remodeling: Phase 4

Cement board installation can be daunting.

Especially if you’ve never done it!

Our previous tutorial shared how to choose the right bathroom backer boards in order to avoid a moldy bathroom.

Cement board is a huge part of a bathroom renovation because it doesn’t contain any organic matter for mold to use as food.

Today, we’ll share how to install cement board in a bathtub surround.

Plus we’ll discuss what materials are needed to do the project correctly.

Let’s dive in.

Here are the supplies you need

Let’s start!!


Determine Where Cement Board Location

The first step in any cement board project is to determine where you want it.

In our case, Rob (my brother-in-law whose bathroom we’re working on) wanted the cement panels in the shower surround but preferred to have fiberglass faced purple board serve as the top border.

Determine Where You Want Cement Board Installed

It helps to know the dimensions of a typical cement board panel.

They are either 3 ft by 5 ft or 32 inches by 5 ft.

The manufacturers do this because bathtub surrounds typically have a back wall that is 5 ft long.

And both adjacent side walls are anywhere from 32 to 36 inches wide.

This makes installing cement panels much easier  because it involves less cutting.

The Bathtub Back and Side Wall Dimensions Fit the Cement Board Dimensions

Ideally you want the cement board to cover any area that will be exposed to water.

I don’t know about you but the front wall that contains the showerhead in our bathtub gets saturated with water.

This is a good reason to choose the 36 inch wide cement panel because it will extend out more and add protection against mold forming on any existing drywall that is paper faced.

Make Sure the Side Wall Cement Board Panel Extends Beyond the Bathtub Width

Choose the Correct Screws and Joint Tape

When you buy cement board it requires the same installation materials as drywall but with a twist.

You’ll need to buy cement board screws that have a special corrosion resistant coating and are much stronger than drywall screws.

Cement Board Requires the Use of Alkali Resistant Screws

In our prior tutorial we discussed how fiberglass drywall joint tape should be used to make wallboard panels one cohesive unit.

The same principle applies to cement board.

The tape you need to use is alkali-resistant, fiberglass-mesh, and polymer coated.

The polymer coating on the tape protects it from the chemicals in the mortar within the cement board itself.

This tape can also be used where cement board and drywall meet each other.

Cement Board Tape is Alkali Resistant and Can Withstand the Harshness of Cement Board

Instead of using drywall joint compound to embed the tape in the cement board you should use thin-set mortar.

We utilized the same thin-set that will be used to attach the tiles.

Use Thin-Set to Embed Cement Board Tape into Cement Board Joints

Having the cement board, alkali-resistant screws & joint tape, and mortar will get you one step closer to installing the tub surround the right way.

Start With the Back Wall

We installed the upper back wall panel first.

Since the width of the back wall was a little more than 5 feet wide we simply installed a full panel without having to trim it.

I spaced the screws on the studs about 8-10 inches apart from each other.

Attach screws at most 1/2 to 1 inch from the edge of the cement board.

Otherwise, the cement will crack.

Attach Cement Board to Studs and Space Screws 8 to 10 inches Apart

I prefer to add screws to the top of the cement board then use a level to trace a vertical line indicating the stud position behind the cement panel.

Unless you’re Superman or Superwoman it’s hard to see through cement and this step makes me feel better about the screws being directly centered on the studs.

Use a Level to Mark the Stud Positions Behind Cement Board Panels

To make the process easier I highly recommend using an impact drill/driver like this Ridgid I’m holding.

This is hands down my favorite tool and if you’re doing any DIY projects you need to buy an impact driver.

Use an Impact Drill:Driver to Attach Cement Board Screws

The Americast bathtub we installed had a good 1 inch lip on it, which we attached to the studs using galvanized roofing nails.

We also shimmed out the walls with 1/4 inch lath strips so the cement board would sit flush with the lip or slightly beyond it. This same method can be used for Wedi, KERDI-BOARD, or Hydro Ban Board.

This will allow the tiles to rest beyond the lip of the tub when we secure them to the cement board later in the project.

I measured the distance from the top of the nail (holding the lip to the stud) to the bottom of the upper cement board panel and subtracted an 1/8 of an inch.

This gave me the size of the bottom cement board.

It’s important to get this measurement correct because it’s tough to cut 1/2 inch from cement board!!

Measure from the Roofing Nail to the Bottom of the Upper Panel

Once we obtained the height of the bottom cement board panel I cut it using a special carbide tip knife and the straight edge of my level.

Since the cement board is sandwiched between fiberglass mesh tape it needs scored until the mesh is fully cut.

I scored one side of the cement panel until the mesh completely severed.

Use a Carbide Tip Cutting Knife and Level to Trim Cement Board

Then I bent back the scored portion of the cement panel to expose the other side of the mesh tape.

You can either cut the tape with the carbide tip knife or cut it with scissors.

The lower cement board panel was installed just like the upper portion, and rested just above the lip of the tub.

One big tip is to make sure the tapered edges of both the lower and upper panels abut each other.

This is super important because it provides a recessed space for the joint tape to sit in.

Otherwise, you’ll have a hump at the joint and this will cause your tile installation to be uneven & look bad.

Make Sure the Tapered Edges of the Cement Board Abut Each Other

Our back wall was pretty simple to install.

The two side walls are straightforward as well, but I’m going to explain how we attached them to the studs in our next tutorial. Also, it’s critical to check the depth of mixing valves before installing cement board.

There are some details I feel are really important to share and that’s why there will be a Part 2 to this tutorial.

What’s Next

Hopefully these tips helped.

If you’re interested in an easier alternative to cement board then both KERDI-BOARD and Wedi are great options.

If you’re doing a bathroom remodel and need help, join one of our online courses – they’ll make your bathroom renovation much easier!

Let me know if you have any questions and I’ll do my best to help.



Cement Board Installation

  1. Eddy says:

    Thanks for the helpful info. When you hang the cement board, which side is facing out – the smooth or the rough? Does it differ depending on what kind f tiles are being used? Thanks!

    1. Hi Eddy,

      Nice question. The rough side of cement board is the side to hang the tiles on.

      Usually there is a sticker on the board that provides you with directions, though.

      So always read that sticker to be sure of what to do with your specific material.

  2. David Henry says:

    I saw your pictures about doing a tub bath above but did not see anything indicating what type of joint compound to use when joining purple board to cement board. I was told to definitely not use drywall joint compound. I used thin set to join the different pieces of cement board, but since I have a 12″ border of purple board setting above the cement board, I need to know what kind of joint compound that I should use to tape and bed the joints between the purple board and the cement board.

    1. Hi David, we used setting type joint compound that needs to be mixed with water. I prefer this variety over pre-mixed because it dries quicker and becomes rock solid. All the cement board joints were done with thin-set and not joint compound. You can also use thin-set to tape and bed joints between the purple board and cement board. Just make sure the thin-set is a bit thin (pardon the repetitive nature of this discussion) so that when you tile the transition there won’t be a hump that will make your tiles look offset. Hope this helps but let me know if you need more detail.

      1. David Henry says:

        Thanks for the reply about my question as to what type of joint compound should be used when joining purple board to cement board. Remember that I am using a combination of cement board and purple board for the shower walls. The purple board will go above the cement board, for about 12 inches, until it meets the ceiling which is also purple board. You suggested a setting type joint compound and said that thin set, mixed so that it is very thin, could be used. I noticed that when I used thin set on the cement board joints, the joints were pretty rough because of the cement board surface. This didn’t concern me because I new that the 1/4″ adhesive for the tile would basically smooth out the joint. Now, with the recommendation to use thin set (very thin) between the purple board and the cement board joint, I am concerned that it is going to cause the joint to look pretty rough ? I plan to light texture the purple board so I wanted to have a smooth surface, like when using regular dry wall joint compound. Will the thin set, very thin, produce a smooth joint on the purple board side of the joint ?

        Thanks for your help.

        1. If you tile over the thin set joint the rough texture won’t be an issue. But if the joint will be exposed then yes, it’s probably best to use the setting type joint compound instead. Great questions David and always feel free to send a video or pictures to me at [email protected]

  3. PJ says:

    We are re-installing shower doors after a bathroom tiling job, and they are a little narrow, as they were before. In the downstairs bath (which someone did before we moved in), they used a painted 2×4 or something close as a shim on one side, overlapping the edge of the tile. They fastened the shower frame to that, and to the tile on the other side, and then used a painted wood trim down that one as well. Is THIS a workable idea? If not, how can we better finish the frame installation on this second bath? We have tiled it flush with the outer edge of the bathtub, and it is a quite unfinished look which wasn’t a concern at the time, since we intended to use the wood trim. Having second thoughts now, and have seen info on the schluters trim. Is it still possible to use this type of finish? (It looks as though it is installed when mortaring in the final edge tiles, but perhaps there are alternatives?) ANY ADVICE is greatly appreciated. Thank you very much.

    1. Hi PJ, thanks for your question. Schluter trim is a great option and can be used when tiling. It is embedded into mortar then tiled over.

      Can you send me a few pics of your situation and we can come up with a solution 🙂

  4. Nate says:

    I am using concrete board in my shower and am having a hard time getting the screws recessed even with an impact driver, what can I do, I am hesitant to use a hammer on them.

    1. Hi Nate, as long as the screws are only a fraction of an inch off the board you should be okay. But if they’re more than 1/16 of an inch off the panels you’ll need to get them more flush.

      What kind of impact driver are you using?

      1. Nate says:

        A dewalt and no matter what bit I use it has tendency to just spin in the head even at low torgue as if the studs are made of concrete

        1. Hmmm, what size or length screw are you using? I wonder if the screw isn’t long enough to really bite the stud. You’re totally right Nate, the screw shouldn’t be spinning. It should be super tight and suck the board to the stud.

  5. Chris L says:

    Hi Jeff,

    Your site is fantastic! My shower grout cracked, allowed water to get into the drywall which then buckled the drywall and creating a bigger grout gap. Sadly water got into these gaps and saturate & molded the drywall behind it. Now I’ve gutted the bathroom and am doing research comparing cement board to green board. This is how I came to your site 🙂

    I’ve never used cement board but am eager to learn. However, I just wanted to clarify a few things first. According to above, you leave a 1/8 gap between the top “lip” of the tub and the cement board. Is this gap for expansion? Also, I’m a little unclear as to what you use when mudding where drywall meets cement board?

    Thanks again!

    1. Great questions Chris.

      Definitely use cement board instead of green board. I suggest shimming the studs (only if you have to) to get the cement board down over the tub lip. The cement board should be plumb, hence the need for shims sometimes.

      You can then caulk the 1/4 inch gap between the bottom of the cement board and top of the tub. There could be a bit of expansion and contraction and that’s the reason for the gap. There shouldn’t be much since it’s cement 🙂

      You could use either setting type joint compound between the cement board and drywall or thinset mortar. I like setting type compound since it dries hard and is sandable. The tile should go over it any way. And you can add a water proofing membrane to this transition in the form of RedGard.

      Hope this helps a bit

      1. Chris L says:

        Hi Jeff,

        The drywall edge that meets the Hardibacker is the factory “finished” side (the side that slants downward). Thus creating a gap in the depth of the two meeting surfaces. You mentioned using setting type joint compound but would you also use tape? I didn’t know if this would possibly cause a hump on the Hardibacker where the tiles sit?


  6. Brittney says:

    Thanks for sharing this informative post. I don’t think I am as great at DIY as you are, so I may need to hire a professional. Great job!

    1. You can totally do this kind of stuff Brittney. I’m no DIY guru. None of us are gurus.

      Let me know if you have any questions, I’d be happy to help 😀

  7. Emily M says:

    Wow – your site is GREAT! Just what I’ve been looking for – I’m a novice to everything home related, but I figure I have to learn somehow, right? I’m updating my bath/shower and I have a question if you don’t mind. I ripped out everything to the studs in the shower area (40 yrs old, so of course found drywall, not cement board) plus an extra 3 inches out, similar to what you do above. But, the studs are positioned in a totally not helpful place for attaching the cement board – 15 in apart, like 7 in in from the edge of the tub and therefore 8 inch out. Plus I found some other plumbing and electrical work behind the walls along the edges, so just adding a stud would honestly be above my pay grade right now. I know it’s important to attach the edges of backer board to actual studs all the way around, but I don’t feel confident in adding those with so much going on behind the walls. So, what I think are my options: 1) hire someone to come in and just add the studs, 2) rip out the drywall further to the next stud, which would be about 8 inches past the edge of the tub, or 3) is it possible to add horizontal 2×4’s just in the places that need screws? That could be horribly against code or something, no idea, but that would definitely be more possible for me to do than adding a full floor to ceiling stud. What might you suggest? Thank you so much! Seriously, your site is so great and helpful.

  8. Jennifer Zhu says:

    Hi Jeff, what would you recommend to use, thin-set cement, ready mixed quick set cement or concrete? I read that they settle to different levels. Thanks!

    1. Are you using the thin set for tile Jennifer?

      If so, I like mixing the thin set myself. The consistency for tile should be such that the ridges stand up when troweled over the substrate.

      Now, if you’re laying down Ditra over your wood subfloor or cement floor the consistency of the thin set should be a little thinner.

      I guess my point is that the thin set allows you to mix it to different degrees for different materials and gives you options 😀

  9. Anne Marie says:

    Can you please clarify something for me. So the cement board gets hung about 1/8-1/4″ above the flange of the tub. I will put a bead of caulk where the cement board and the top of the tub flange meet. My concern is when starting tile. What about that hollow portion behind the bottom of the first row of tiles at the tub level up until the cement board starts? Do you put mortar for tiling to try and fill up the space. I’m concerned of it being able to STICK to shiny new porcelain tub. And after its tiled I feel it will be weak at the tub level. I hope you understand what I’m asking.

    1. Great question Anne.

      After caulking the transition between the tub lip and cement board you can fill the space between the tub and the cement board with thin set mortar. Make sure the mortar is plumb and level.

      Let it dry and then you can apply a waterproofing membrane over the cement board/mortar.

      I personally like RedGard or think you should explore Kerdi by Schluter for your membrane.

      All this combined will ensure a solid surface for your tile.

      Let me know if you have any questions

  10. Ashley says:

    My husband and I are removing our current tile shower to replace it with a fiberglass 4 piece shower stall. Only problem is, once we removed the tile and drywall, it doesn’t seem the shower walls will line up perfectly with our studs. Any advice so we have something to screw in to? Thanks!

  11. CJ says:

    If my tub is 5’X31″,what size of direct to stud tub surrond would I need

  12. Lisa says:

    What about a vapor barrier between the studs and cement board? Is this required? If you’re using Redgard on top of the cement board, is this why no vapor barrier is needed? Thanks.

  13. Andrew says:

    You mention using cement board on the ceiling, but my question is can you paint cement board? Or should it only be used where you plan to tile?
    I have an 50 Sq ft bathroom and was thinking about using cement board for the whole thing, but I was told you can paint it and we are only tiling the lower half of the walls outside of the shower.
    Thanks in advance!

  14. Ed Branscum says:

    I’m working with cement board but I need to cover a couple of 1/2 inch strips and every time I try to cut the cement board I score it deeply on both sides but it crumbles into a million pieces, is there a trick for this?

  15. Ross says:

    Hi Jeff,
    Were having a Vikrell surround installed. Is there any reason to tape or finish the cement board behind surround?



  16. Donna Adams Ruckart says:

    When there is a gap between the top of the cement board and the ceiling should the gap be filled with thin-set mortar or waterproof caulk before the cement board walls are waterproofed?

  17. Marcus says:

    I am putting tile up in my bathroom and I have installed durock backer board my question is that the existing sheet rock is higher then the backer board should I just fill it in and water proof it of do I need to take another step to even it out be for I go any futher

  18. Syafique says:

    Hi Jeff.. im syafique from malaysia.. currently building my house using cement board.. i got a question.. i would like to install a tile in a shower room.. can i install tiles on cement board at 10ft high??

  19. Stacey Kulick-Hart says:

    We just installed a three piece tub surround. We are now installing hardy cement board around it. We are having a difficult time figuring how to tile up the outer sides. Do we put the cement board over the flange then tile up to the edge with a 1/8 space? It is not a straight line along the surround edge. Not sure how to tile and have it look nice. Hope I explained Myself correctly. I thank You for your time and consideration.

  20. Nitin says:

    Hi Jeff, great site, full of practical information for people like me. I am in the middle of a tub to shower conversion. The older tiles didn’t go all the way to the ceiling and I’d like to keep it this way. One of the walls has a half moon shaped window and the tiles stop at about the window plate height. I made the mistake while removing the older tiles by making a cut into the drywall at upper most edge of the tiled area. Now when I abut the kerdi board with the drywall there is no room for mesh tape to easily overlap the existing painted drywall above the tileable area. I say tileable area as I don’t want to raise the height of tiled area any more than what it is right now as then the new height will be not be flush/close to flush with the lower edge of the window and that won’t look nice (existing edge is slightly higher than the window’s lower edge). On the sidewall luckily I removed the tiles without removing the drywall behind them so I can tape kerdiboard to 2″ of drywall and then cover the overlap with tiles, but on the upper intersection the 2″ required from drywall side has to come from the drywall side beyond the tileable area and it will be visible. I’m trying to plan the best approach to deal with this. One of the option is to remove the high gloss paint for 1″ and then embed seam tape and after tape and mud, and then paint it. The wall is textured and I’m not sure if my limited taping skills and any paint mismatches will ruin the look. Is there any way to handle this intersection which can keep the paint as it is and not raise the height of tiles to cover the seam. Thank you.

  21. Adina Trusz says:

    Thank you for such great advice and links- I ripped out my tub and putting a standing shower. Any videos/ pages on that? Should the cement board be behind my shower pan or above it? Can I use the cement board on the floor? Especially the entire bathroom?

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