What Is the Best Backer Board for a Shower?

For a tile shower we use waterproof foam board, GoBoard specifically. Half inch on the walls, and two inch where we are building a bench or fabricating something structural.

But they all have their place. Which one is right depends on the shower build itself, on what the customer needs, and on the budget. So here is the honest comparison rather than a brand, and here is when something else is the better call.

Is backer board waterproof?

That depends on which one. And none of them are waterproof as an assembly on their own, because a board can be waterproof and the shower still leak. Water finds the seams and the fastener heads, not the middle of a panel.

The four kinds of shower backer board

Cement board. Durock, HardieBacker. It is porous, so water passes through it and the entire panel has to be waterproofed, not just the seams. That surprises people, because it is the board most often described as the one you use in a wet area. It is low cost and durable, and it is heavy and hard to cut. It is more impact resistant than anything else here and it does not bow when you fasten it. It will break, though, if you try to bend it over an uneven surface or if you are not careful cutting it, and what you are left with is a jagged edge. Depending on where that edge lands, it can be difficult to waterproof, which means pulling the board back off and starting that piece again. Where it earns its keep is heavy-use construction, a commercial building rather than a house bathroom, or anywhere an extremely rigid, flat surface is necessary.

The other three are waterproof tile backer boards, which means the waterproofing goes on at the seams and the fasteners rather than across the whole panel.

Waterproof cement board. PermaBase WP. Seams and fasteners only, which is the advantage you are paying the higher price for. Still heavy, still hard to cut.

Glass mat gypsum. DensShield. Similar properties, and lighter. It is gypsum, so it cuts like sheetrock, score and snap, and then you run a rasp over the edges to get them smooth. It also breaks easily, for the same reason drywall does. And the waterproofing is on the two outside faces with gypsum in between, so if a fastener gets run too far through it, or it is not cut cleanly, that core can crumble.

Waterproof foam board. GoBoard, Kerdi-Board. Waterproof, lightweight, and you can fabricate curbs, benches and niches out of it. It comes in different thicknesses for different uses. It costs more than cement board, and how much more depends entirely on which one you buy.

One caveat runs across all three of the denser boards, and it is the one that matters most in a shower: you cannot cut small pieces out of them. Anything under about two inches wide will snap off, either while you are cutting it or later while you are fabricating with it. That is what makes building a curb, a niche or a bench out of them difficult, and it is where foam board pulls ahead.

Those are 1/2 inch four by eight sheets, priced August 2026 at Home Depot, Lowe’s and Floor and Decor. You can go and check them. Cement board is also sold as a three by five, which is half the coverage, so compare per sheet with care.

GoBoard vs cement board

Three reasons, and the third is the one that decided it.

Weight and speed. Foam board is lighter, quicker to put up, and waterproof. On a second or third story bathroom the weight matters on its own. It also takes less time on the job, which means we are in and out of your house sooner.

The cost is not what it looks like. GoBoard is $57.98 a sheet against $35.99 for cement board, about $22 more. A 60 by 32 shower, eight feet tall, takes three sheets. So the difference across the whole shower is roughly $66, on a shower that averages around $5,200.

With a contractor who knows what they are doing there is real saving in that sixty six dollars, because you are paying a bit more for a better product instead of paying more for the extra labor a heavier, harder-to-cut board takes.

Fabrication, which is the real one. Curbs, niches and benches are built out of the board itself, and that means narrow pieces the denser boards will not give you. Built out of cement board they are also very hard to waterproof correctly. Those are the failures we find most often on the showers we get called out to repair.

That is not a claim off a brochure. It is what we see when we open showers up.

GoBoard or Kerdi-Board

Both are foam board, and Kerdi-Board is the name most people have heard.

We use GoBoard. It is denser, so the same board works on walls and floors. It is easily repaired if a tile ever has to come out, and the cementitious face makes it straightforward to reseal if it has to be pieced back together. It runs less than half the price: $57.98 against $129.28 for a 1/2 inch four by eight sheet.

Schluter does make products designed to work with Kerdi-Board, including benches, niches and drains, and it resists moisture wicking in a constantly wet area. That is a real advantage in the right situation.

Kerdi-Board is not a bad product. The premium buys a name brand rather than a better result for what we build, so we cannot justify it. We would use it at customer request.

What thickness backer board for a shower

• Half inch on walls. That is the standard.
• Two inch for benches and any structural fabrication built into the shower.

The shower floor is not backer board. That is the pan, and ours is a preformed Kerdi tray.

The part that decides whether it holds

Whichever board goes up, the assembly is what keeps water out.

Every joint gets sealed and then reinforced with membrane, either Kerdi or FloFX. Corners, changes of plane, the wall-to-pan transition, around the niche, every fastener. Those are the places a shower fails, and they are the places that take the time.

If you are reading a quote that names a board and says nothing about how the seams are treated, you have been told the easy half.

The rest of what we build, and why, is on our custom showers page. Call (864) 747-9325 for a free estimate in Greenville and across the Upstate.

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