Cement board installtion for reno shower
Hello all,
I am renovating my bathroom and would like people’s opinions on the install. I am not going to get into the discussion of CBU vs. Densshield tile backer products, but for the record, I am gong to go “old school” and use CBE (Durock to be exact). I don’t need to (or want to) rip all of the drywall out of the existing bathroom, but I will need to rip out quite a bit to make room for a much larger shower. The curent layout is a 9 x 9 bathroom, with a huge closert and a small (32 x 30) shower??? So, I am making the closet and shower into a huge shower. Sorry for the details, I can’t help it!
I have 5/8″ drywall existing in the bathroom, and I don’t want to get 5/8″ CBU b/c it’s going to be very tough to work with. I was thinking once I rip out the drywall, I was going to put insulation in the wall, use 6 mil poly wrap, put 1/8″ sheet of ply, then use 1/2″ CBU. I know it’s only 1/8″ difference, but the 1/2″ is more readily available and that much easier to use. I was thinking of putting up 3/8″ ply, and using 1/4″ CBU, but I’m afraid that won’t be thick enough?
So – here’s my question:
– would you use 1/8 or 3/8 ply under the CBU (i.e. 1/2″ vs. 1/4″ CBU)?
– should I use 6 mil poly under the ply, or would you use something else (felt paper, etc.).
As always, your opinions are appreciated!!!!
Replies
I've never seen 5/8" CBU.
3/8ths Plywood with 1/4" CBU is fine.
If I was doing it, I would use pressure treated plywood and, in the last couple of years, I've been using Ice and water shield between the ply and the CBU.
Now if you really want this to go well, I would suggest using the Kerdi waterproofing system over the CBU and for the pan waterproofing over your preslope.
After using it in the last couple of showers, I will never even consider the PVC pan liner....ever!
For the record, old school would be mudded walls.
You need to find out what true "new school" technology can do for you, by heading over to the John Bridge tile forum, and finding out everything about Schluter systems.
You'll get some opinions here, but the readership and forum size is much much larger over there. And it's all about tile. Nothing else.
Schluter's membranes, Kerdi for showers and Ditra for floors, are absolutely waterproof, absolutely. Their drain system, the Kerdi drain, makes your clamp-onto-the-pan thing with the gravel weeps look like stone age technology.
Find out what today's professionals are doing.
Grandchat27,
Ditto what Gene Davis says in post #3, above. I did a Kerdi shower over CBU recently, and loved it. John Bridge sells an e-book on the Kerdi system; I bought it and found it helpful.
Kerdi can be used over drywall, but I prefer CBU because of possible water intrusion at penetrations. With Kerdi, the back of the CBU should be open to the stud bays so any water that gets in can dry to the wall. It sure won't dry out through the membrane!
Bill
Edited to add: Kerdi over 1/2" panels will be close enough to 5/8" that thinset can manage the rest of the difference. Be careful of Hardibacker 500, though. They should rename it Hardibacker 375, because it is only 3/8" thick now. Weird.
Edited 8/26/2006 1:53 pm by BillBrennen
Do this with your leftover Kerdi. Make a cube box, open topped, with some scrap OSB. Say about 12 x 12 x 12 high.
Now make up some thinset and Kerdi the inside of the box, bottom and sides. Lap your joints and bond with thinset just like you would in doing a shower. Since you are working in a small space, you might need to be using a putty knife for some of the detail work.
Let it cure. Fill it up with water and set it somewhere where you can check in to see what is happening. Add water to account for evaporative loss.
That is least a 10 inch head you'll have on those joints. You won't see a leak, ever. Guaranteed. Guy's got one going here that's been filled for more than 4 years.
Forget the durock in the future. Just do the Kerdi on gyprock, like all the pros do. Spend your savings on some tile, instead.
Gene,I am already convinced about the watertightness of a Kerdi membrane. My redundancy was intended to protect at the penetrations like the valve (6" diameter hole), the two shower heads, any future grab bars or hooks, that sort of thing. The screws that hold the grab bar I mounted are fully sealed, but I cannot control what happens after I leave the customer's home. They paid for the CBU and labor, not I.Bill
well, i've used 5/8" wonderboard, but i doubt i'll ever use it again. it was insanely heavy in 4x8 sheets and was ridiculously expensive.
1/8" plywood ? never heard of it.
plywood under the Durock ? i guess you could, probably give you some extra density in the walls. not really necessary though.
1/2" ply and 1/2" Durock are your most common products, i would probably stick with them. felt paper between layers.
waterproofing membrane as recommended over the Durock is certainly a good recommendation. if you used the membrane, i would might consider skipping the felt.
on a design note, have you ever been in a huge shower ? what are you thinking about doing in there ? yoga ?
just a thought. big showers tend to be on the cold side when showering. they also have a locker room feel. bigger isn't always better. i think a woman told me that once.................
carpenter in transition
If you're compelled to have a 5/8ths" thick wall to match adjacent 5/8" thick drywall, then rip a bunch of 1-1/2" wide by 1/8th" thick strips off a 2x4 or 2x6 and tack them to the faces of your existing studs.
If using a 40-mil thick CPE or CPVC liner for your mambrane, hold those 1/8" thick strips about 8"-10" off the floor, or the height that the membrane will come up the wall.
That way the membrane will be stapled to the original framing, and the CBU will not be bowed out by the thickness of the membrane, "kicking it in" at the bottom of the walls. Especially in the corners, where the membrane ends up being folded over on itself.
Then use 1/2" CBU over the 1/8" furring strips and down over the membrane.
I'm a fan of Kerdi, but I do it over CBU not drywall.
Mongo
Mongo
Thats a good looking shower, nice work.
Doug
Thanks.Not one uncut tile in that whole thing. Gave the Felker a workout.Mongo
Very nice shower. Thanks everyone for their help.
I think I am going to go with 3/8" ply w/ 1/4" CBU w/ either poly or fire and ice shield in between the poly and the CBU. I am not familiar with the Kerdi product, but I will strongly consider it after reading up on it more.
Quick question - the reason I want such a big shower is b/c I am instaling a steam system. Do you think the Kerdi would be affected by the steam system? I think no, but I thought I would throw it out there. Thanks again!
On the contrary, if you are doing a steam shower, that really changes things. I highly encourage using Kerdi.For a steam shower you'll want a waterproof membrane on the walls, floors, and ceilings.The beauty of a topical membrane such as Kerdi is that the tile is thinsetted directly to the Kerdi. Thus, whether is be water, or steam, the only thing that can get wet in a Kerdi shower is the tile, the grout, and the thinset. Moisture cannot penetrate deeper into the walls (into the CBU) or into the floor (deck mud).If doing a steam shower, I HIGHLY recommend you use Kerdi.Mongo