In Tom Meehan’s article “Installing a leakproof Shower Pan” Aug/Sep 2001.
Tom shows a curb built with three 2×4’s. Here’s the attached drawing from the article.
I’ve got two questions:
1. The article doesn’t mention how he finishes off the curb. I would assume he uses metal lath and packs in some morter on all three sides. Is that the correct way to finish off a curb?
2. Three 2×4’s seem kind of short since I’ll be packing about 2-3″ of mud in the bottom of the pan to start with. That would only leave about a 2 1/2″ curb from the inside. Is that ok?
Replies
Here's how I do it. The membrane runs over the curb and is fastened only on the outside. I then bend metal lath over the curb so it holds by preshaping so it will clamp on the curb This gets buried in thinset and backerboard goes over it on the outside.
You can see my before and after pics.
The height of the curb is based on the distance above the drain surface. Three inches should do it. Depending on how far your curb is from the drain will determine how high the curb actually appears where it meets the shower floor.
I find my distance above the finished drain height with a laser. put the tape on the drain and set the laser at, say 20", and transfer the mark to the wall. Now measure up 3" and then down 20" to get your curb height reference point. Or just measure down 17". Using an even number makes it less likely to make a math error.
If the curb is far enough away, such as in a wheelchair-accessible shower, there will only be a hump instead of a curb.
Hey thanks for the info and pictures. How much thinset do you put on over the metal lath? 1/2"? Here's the drawing I forgot to post last time.
The article from last year showed him NAILING CBU into the curb and then tiling the curb from there, with some Redguard over the curb to seal the nail holes in the CBU. Ugh. That is bad.I just wrap the 2x4's with a membrane nailing on the outside of the curb only and using roofing cement to hold the membrane tight against the 2x4's. Then make a 3 sided section of diamond lathe which is folded so it is very very tight against the verticle curb surfaces and nail it in place on the outside only. Then buy some fat mud also called wall float and smear that stuff on the curb using the wall's CBU's as a screed to set thickness and strike it off with a straight edge on both inside and outside. For the top, make it any thickness you like--but try to slope it a half a bubble so water flows from the outside of the curb to the shower pan, not visa versa.Here is an article:
http://johnbridge.com/shower_curbs.htmRegards, Scooter"I may be drunk, but you're crazy, and I'll be sober tomorrow." WC Fields, "Its a Gift" 1934
You want to have the lathe conform fairly well to the membrane without puncturing it. Once it is embedded in thinset, it is not going to move or cause damage. Since neither the membrane nor the lathe will be perfectly shaped to the shape of the curb, 1/2" is about right for what you will need to cover it.
You can make it thicker without causing any problems. The CBU on the outside of the curb helps to get a nice surface for the tile. You don't want to attach tile out there with just some lathe over membrane, as this does not offer as much support as CBU.
I also slope the curb toward the shower. This is done by cutting an angled 2X4 on the table saw. By the time you get the different layers of materials on the curb, it will be about 6" wide. I like to have a 1/4" height differential over this area. If any moisture should get through the curb over the years, it will follow even a shallow slope toward the shower side.
If you do not slope the curb before you install the membrane and choose to slope the thinset instead, it will be better than no slope; however, any water that gets through will be able to run to the outside of the curb, which is to be avoided.
No reason to be putting 3' of mud in the base.
My perimeter screed is 1 3/4" then slopes to the drain. In a 5' shower I'll slope it 1/2" to the drain. Plenty.
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I use Kerdi for showers, so I won't answer your first question about the curb structure. Others have gotten to it.
As far as the second, regarding curb height, code simply requires that the finished curb height be a minimum of 2" above the top of the drain.
Mongo