Installing cement board behind my shower

[KatrinaK]

Hi Everyone,

I am remodeling my bathroom and am at the stage where I need to put the cement board up behind my shower. There is some vapor barrier there, but on the interior walls it only goes about half way down the wall. Does anyone have any thoughts on if I need to add more vapor barrier? There used to be drywall behind the shower, I'm not sure if having cement board now changes things?

Also, I am not sure how far down the cement board should go. The drywall that was there previously looked like it was just above the tub line, not touching it. This is one of those shower/tub combos.

Any thoughts on this would be greatly appreciated, I am very new to the do-it-yourself world!

Katrina

[jadnashua]

You do want a vapor barrier and bring it down lapped over the tub's tiling flange. You only need the cbu up to the height of the showerhead, but you can go further. To keep the cbu from bowing out, you can shim the studs, notch the studs (and recess the tub's flange so it is flush with the studs), or stop it slightly above the flange and make sure the tile is more than half supported on the cbu. The tile should not be touching the tub, but a slight gap that is caulked.

[KatrinaK]

Thank you Jim, this helps a lot !

[johnfrwhipple]

Katrina look into waterproofing products as well.

For another $70.00 you could make the entire tub surround waterproof.

Products from Mapei and Laticrete would be Aqua Defense, HPG and Hydro Ban.



The green product is Hydro Ban in this picture. You can see I used a waterproofing chalking to fill the tiny gap between the backer board and tub. This was done after I waterproofed the tub.

There are sheet membranes from many companies like Kerdi, Noble Seal TS, Noble Wall Seal, Jaeger, Wedi and on and on. The ones that allow modified thin-sets I think are best so avoid the Kerdi membrane if you can.

The Vapour barrier behind your interior walls is to provent moisture from wicking through the grout and the cement board. Why not stop it first before it even gets there?

Make sure the cement board does not flex when installed. Many home owners use under powered drills that do not set the board tight to the wall stud.

Tape the seams of the cement board and do not pin the cement board tight to the tub.



This is a free standing tub that sits into a corner. On the right side is an exterior wall and the left just a regular wall. On this project the entire home was spray foamed so no vapour barrier was required. The blue product is Mapei HPG a one step waterproofing system. I brought the waterproofing down the cement board and onto the tub deck. Later like the other project I used a little Kerdi Fix.

Good Luck.

JW

[galerie]

Can LATICRETE Hydro Ban be installed on Durock Backberboard?

[mtcummins]

Correct me if i'm wrong, but I believe you should NOT have both a vapor barrier behind CMU and waterproofing over it. Its one of the other, and the waterproofing over CMU is the better option by far.

Personally, I use Kerdi on walls and Ditra on floors with modified thinset (typically versabond), with no problems. I know that John Bridge over at his excellent tile forum (that JW above doesn't seem to like too much) does the same at least with Ditra, and he's been doing it a long time w/o problems. However, it will void the warranty if you're worried about such things, so its your call. The other options he suggested are also good ones, I just happen to like Schluter's products.

Can't tell you about hydroban on CMU, maybe someone else can, or read the specs on it. it should tell you the suitable applications.

With most waterproofing, CMU is overkill, though I like its stability and sometimes will use it. With Kerdi, I generally just apply directly to MR gyp board. Not sure what the other waterproofing methods require, but this is how Kerdi is specified to be installed.

[johnfrwhipple]

Can LATICRETE Hydro Ban be installed on Durock Backberboard?

Off Course.

Hydro Ban is an excellent product and if you go this route you will have many options in thin sets for the tile setting. With newer larger format tile it's nice to get the anti sag mortar (this is modified thin set) and with Hydro Ban you can use it.



Here is a look at more Hydro Ban installed in a walk in shower. Using a liquid waterproofing also aids in simple shower niche construction. Remember that a niche can not go on an exterior wall as it will not have any room for insulation.

It's true I don't care much for the Schluter's line of products. There is not much to like about them. For one it is the thinnest protection in waterproofing products at 8mil and one of the hardest to work with. When setting Kerdi over Durock you need un-modifed thin set and this dries very quickly when the Durock steals the moisture from the thin set. With modified thin sets you have a longer working time and a little more forgiveness. I could be wrong about Kerdi being the thinnest membrane - does anyone know of a thinner product? Noble Seal TS is 30 mil. Think about it. Your credit card or bank card is about 30 mil thick. Kerdi is roughly 1/4 that thickness. Hydro Ban is 20 - 30 mil when installed properly as are most liquid membranes. Each coat thicker than Kerdi.

You can use Noble Seal TS if you like sheet membranes and this like Hydro Ban allows for installation of all thin-sets without voiding the manufacture warranty.

Remember that your local building inspectors will require you to follow all the manufactures printed guidelines. This is my core beef with the Schluter product line.

Versa Bond is a cheap thin set and Kerdi the thinnest protection to my knowledge - for my clients and customers I demand more.

John Bridge is retired, he no longer sets tile for a living - John send me an email a couple years back saying just that. I believe John Bridge sends his refferals to a setter named Paul now. I believe John Bridge's income comes from selling products from his online tile store and selling Kerdi EBooks. I make my living installing showers and waterproofing showers. It has taken me a long time to learn all the different approaches and I don't think the Kerdi product is bad - just limiting and hard to work with. Each user should research these facts personally - Call Schluter and a thin set supplier and ask for the facts.

Often what you are told by tradesmen or by online posters is not what is best for your home but what is best for the tradesman or what is best for the schedule. we use what's best for the client and what offers up my company the best possible product with the least chance of failure.

Why break a manufactures guidelines and your local building department's guidelines? Makes no sense.

Installing drywall in a wet zone is a poor building practice - the worst. I understand that all old loop holes are closing on this method of construction and if you contact the NTCA (of which I'm a member) you will be hard pressed to find anyone endorsing this as an acceptable shower backer board.

Showers should be built to last not build with the cheapest, thinnest products. Shower backer boards should be strong and waterproofed after installing them properly. Waterproofing should be applied topically and all showers should be flood tested - every time. Demand it of your crew.

If you call Laticrete you will get excellent tech support and with the right selection of products build a bathroom with a 25 year warranty.

If you build it with Kerdi and modified thinset you will have no warranty unless you get prior approval - to date I have never seen nor heard of anyone getting an email or letter from Schluter allowing this.


Weighing all the facts it is a pretty easy decision.

JW