Hardi, while not waterproof will not be affected by water. Water will do it no harm. Hardi however will wick water just as any other cement board will. 15lb felt is acceptable as a vapor barrier. If you have already put the hardi up over the felt, just tape and mud it with thinset and you'll be fine.
Backer board = what you are sticking the tiles to. In most cases it'll be a cement board of some sorts. You paint this particular type of membrane onto the cement board after you tape and mud the cement board.
As long as it's Cement Board & not some crappy "almost" cement board stuff. You really don't need the RedGard, but the more protection the better...so go for it. And yes, you can do the boards beforehand.
I’m sharing our experience so that either you can waterproof your cement board or instruct your contractor to do what we did. Like I’ve said before, even if you don’t do this type of work it’s always a good idea to familiarize yourself with the process so that you know a good job is being performed on your behalf.
Before you start a tiled shower or tub you need to install the right wall. One that will be 100% waterproof and support the weight of tile. I’m going to cut to the chase and tell the 3 methods we like
The board itself is waterproof so you don’t have the labor of installing cement board and then waterproofing on top of it. The waterproofing is where they really have an advantage. Usually, they have a urethane glue that you stick the boards together with to waterproof the seams.
Do I need to fix things to ensure a waterproof enclosure? Or, can I just take my chances and hope the combination of cement board, thin set, and ceramic tile will provide sufficient waterproofing? I would like to avoid pulling down the walls I just pulled up, if possible.
A shower is considered a wet application, so you need to waterproof the foundation, which you’ll learn how to do in these instructions. After the waterproofing step, the instructions are the same as if you were installing tile on drywall.
Do I need to apply a liquid waterproofing layer (redgard) on the cement boards before laying down the tiles with thinset? I would think that makes sense since ovbiously the cement boards aren't waterproof, but I've seen many sites now showing installation of the tiles over the cement boards without any liquid waterproofing.
How to Waterproof Cement Board around a bathtub. Please consider joining my Patreon network. I just started it, but I think it can be a great resource for anyone taking on projects around the home.
the point is, you definitely CAN waterproof durock, but do you NEED to or SHOULD you? In this case, the OP says he already has vapor barrier behind the durock, so you SHOULDN'T waterproof it, otherwise, you'd be trapping moisture.
If so, the most important thing to consider is waterproofing. Cement board, backer board, thinset mortar, tile, grout and sealers aren't waterproof. Cement board and backer board only offer dimensional stability in wet areas. In other words, they won’t swell after repeated exposure to moisture in your shower.
If you decide to go this route, no sealant will need to be applied on top of the backerboard, as this could trap moisture between the two layers of waterproofing. Should you decide to use sealant over backerboard, there are a few points to keep in mind.
You do need to use thinset to set the sheets in place on subflooring. You do need to tape and mud all joints and fill screw holes with thinset when planning to waterproof. Cement board is not water proof and needs to waterproofed when used to enclose a shower area.
In other words, how do you make cement board waterproof? Well, the very minimum would be to install a sheet of 4 mil plastic behind the cement backer board or Hardiebacker. However, if you are waterproofing horizontal surfaces like a shower bench then plastic isn’t good enough.
Is a waterproof membrane necessary between the cement board and the ceramic tile on a bathroom floor? I am putting ceramic floor tile in my bathroom ( the shower is acrylic 1 piece). I have two layers of plywood and have the 1/4 inch cement board in thinset and screwed down.
You do not waterproof that, the liner should run a foot or so up behind it, and water on the wall will run down the face of the redgard into the liner. Gravity solves the rest. No, you do not need tape over the screws.
a detailed look at a shower conversion with hardi backer and waterproofing hardi. getting ready for redgard and tile.
No leaks in cement plaster over wire lath. But if you've already taken part of it down and are about to put up a new surface, the cement board only acts as a tile substrate, it doesn't contribute anything towards waterproofing.
To attach the cement board to the studs, you’ll need special 1-1/4 in. cement board screws (see Fig. B). These screws have a coating to resist corrosion, a special wide head with cutting flutes and hi-low threads for a strong grip. If you can’t find them at a home center, call tile specialty stores.