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Retep
08-05-2004, 08:24 AM
Forgive me if this has already been covered. I browsed a few pages of threads and did not find an answer to my problem.

I am installing a mustee 36” neo angle fiber glass shower base (http://www.mustee.com/durabase/neoangle.shtml). Due to the drain cup that protrudes from the bottom of the shower pan and the fact that I have a very shallow drain in the concrete slab, the drain cup bottoms out on the p-trap when I set the shower base in place thus causing it to wobble and not sit correctly. I have determined that I need to build up the floor underneath the shower base about a half an inch. What is the best method for doing this over an existing concrete floor? I don’t want to build up the entire bathroom floor, just under the shower.
I have considered using a tile backer board such as Hardibacker (http://www.jameshardieeu.com/install.html) but really don't think this is a good idea. I have also considered building a temporary form around the shower base and pouring in some type of self leveler or floating in concrete. A friend told me to put down a mortar bed about an inch thick and press the base down into it.
What should I do? Any help would be greatly appreciated.

Thanks,
Pete

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cx
08-05-2004, 08:45 AM
Welcome, Pete.:)

Problem with raising that shower base and not the whole floor is dealing with whatever you pewt under there when it comes time to cover the floor outside.

You say you're bottoming out on the P trap. Sounds unusual. You don't have a vertical "riser" pipe coming up from the trap? Something you could cut a half-inch shorter?

Retep
08-05-2004, 09:17 AM
Hi CX, Thanks for the welcome and quick reply.

I will be putting down ceramic tile on the floor. I think between the thickness of the tile and mortar underneath, I will only have a very small step showing from the buildup under the shower floor. I think a good bead of caulk should conceal this.

The problem with the drain interference is that the old existing drain is 1.5" copper pipe. The horizontal pipe above the trap is only about .25 inch under the surface of the slab. This was connected to 1.5" pvc via a rubber connector with 2 hose clamps on it. Note sure what it is called. the trap is 1.5" pvc with a 2" pvc reducer starting at the vertical and then a piece of 2" pvc as the vertical riser portion of the drain. When the shower base is set in place, the bottom of the protruding drain cup (I call it that for lack of better term) hits the reducer. See fig below. The shower base required a 2" drain thus the need for the reducer.
http://www.mustee.com/images/durabase/SectionalView.gif

Thanks,
Pete

bbcamp
08-05-2004, 10:24 AM
If you can see where the new pvc pipe connects to the old copper (the Fernco fitting), then you can simply make the trap deeper. How did you intend to fasten the "drain cup" to the trap?

Retep
08-05-2004, 11:17 AM
Please forgive my plumbing ignorance.
I was under the impression the trap must be directly attached to the 90 degree elbow coming off the horizontal pipe. Are you saying I can put a small ½” – 1” vertical piece of pipe between that elbow and the trap? That would indeed lower the trap and the reducer thus eliminating the interference and my need to build up the floor. That would be great. :)

The 2” pvc drain pipe extends up into the drain cup. A seal is created by a large force fit rubber grommet. The OD of the grommet is larger than the ID of the drain cup and the ID of the grommet is smaller than the OD of the pipe. I guess it kind of works like a compression fitting.

I know this is not the most desirable shower pan solution, but I am on a budget.

Thanks,
Pete

bbcamp
08-05-2004, 11:29 AM
I'm not a code expert, but I believe they are more interested in the minimum trap depth. Practical matters dictate that the trap be as shallow as possible.

Retep
08-05-2004, 11:36 AM
Would there be any negative effects from moving the trap deeper from the horizontal section of the drain?
Sorry this thread has taken on a plumbing theme, I know this is not the appropriate forum.

Thanks,
Pete

bbcamp
08-05-2004, 02:33 PM
None that I can see.