Shower pan: hydroment over plywood? - Ceramic Tile Advice Forums

bcesa · 12-10-2003, 01:46 AM

My contractor is installing a 48" by 60" shower in my new addition. The new framing is 2x10 floor joists, with a 3/4" plywood subfloor. Deflection appears to be acceptable.

Based on what I discussed with him today, and saw of his work, he has arranged scrap wood around the drain, over which he has nailed a 4x5 foot piece of plywood, using the scrap wood (pieces of cedar shingles) beneath the plywood to create the requisite 1/4" over 1' slope. The plywood seems to flex a little when walked on, and it is somewhat uneven, although all slope is toward the drain. The plywood is secured to the floor with a good number of nails.

Over this he proposes to apply hydroment ultra-set, as the pan. When this cures he will install the tile (1x1" tile on 1 sq ft sheets) over the hydroment ultraset compound.

This seems somewhat inconsistent with the extensive reading I have done in this forum and the liberry. I am concerned that the floor will flex, leading to cracks in my grout, and that the nail heads in the plywood will rise up and poke through the hydroment layer, creating leaks. Also, there is no mortar layer for continuous drainage.

Q: Should I stop him now and insist that a "mud man" be brought into the job, before any (expensive) tile is installed? Or has his proposed method of installation been successful in other applications? This forum seems stronly directed toward the mortar approach, but I cannot find posts that tell me that my contractors proposed approach is trouble waiting to happen.

Q: How does one go about finding a competent "mud man" here in central New Jersey? Tile store recommendations?

Thank you for any and all help. This forum is tremendous! I can't believe what I have learned in two days!

Bill

stullis · 12-10-2003, 01:58 AM

Doesn't sound like a job I would want done in my house!

You best stop him from doing more damage.

I believe there are a couple of members on this board that could maybe refer you to someone who is competent.

tileguytodd · 12-10-2003, 06:48 AM

Bill, at first look i would be scared.however ,i want to check a couple of spec sheets before i take a stand here.Hold tight ok

bcesa · 12-10-2003, 07:05 AM

Tikeguytodd,

Thank you for looking into this further. Contractor showdowns are never pleasant.

Bill

tileguytodd · 12-10-2003, 07:06 AM

Ultraset is designed to be used as a surface applied membrane ,trowelable,it should be applied to a thickness of 30 mils over properly prepared concrete or plywood.They state to not use plywood in wet area's.The material is bridgeable to 1/8" and needs a fiberglass mesh to be used in these area's.This is a good product and very similar to several other manufacturers.
I disagree with the method being used here however.The best way to use this material is as a surface applied membrane and this is how it is spec'd.It should in a shower be applied over a properly sloped mudbed.Would i use this as a membrane,Yes,just not in the method you have described above.
I would insist on a proper preslope,Pan final slope shower or a properly constructed surface applied membrane construction.If this tileman is incapable of building a proper shower pan, i would find a real tileman and have it done properly or, we can walk you through it and you can complete the installation yourself.Surface applied membranes are really specialty type membranes that have no place in basic shower pan installations.they are expensive and require more time than a regular pan to install.generally i use them for handicap type roll in showers and occassionally on on grade slab showers where the slope is buil into the foundation.
I wish you well, thanks for bringing this to my attention.I wanted to look over the spec sheet on the particular product to refresh my memory on its characteristics

bcesa · 12-10-2003, 07:27 AM

Yes, the specification for the ultraset is impressive, but the flexing that is possible in the nailed plywood preslope, and the potential for nails to rise up after repeated flex has me concerned. I will ask him to remove the plywood preslope and start from scratch with a mortar bed. Because the plywood is nailed and also probably glued, my contractor is going to holler, but, oh well! But the ultraset was not appied yet, so it could be worse.

bcesa · 12-10-2003, 12:13 PM

News update and a few more questions. The contractor has removed the plywood base, and I saw him pouring mortar, which is closer to the way John B recommends. But it looked like he was pouring it directly on the plywood subfloor. Will this be a problem if the pan is properly applied above the base mortar?

For the pan he has indicated that he will apply the hydroment ultraset sealer over the preslope mortar that he is apparently pouring now, to about 6 inches along the wall.

How long should the mortar dry before he applies the ultraset?

Thank you.

John Bridge · 12-10-2003, 01:45 PM

Hi Bill,

I think you still have a problem here, and I think you should determine how the contractor is going to complete the job all the way through. I think you should do this before things get really out of hand. I don't think the fella has a clue as to how to build a tile shower.

I wouldn't be using Ultraset at all. I would be installing either a pvc or cpe membrane over an approved pre-slope of mortar. An option on the pre-slope would be one of the foam products approved for that use -- Pro Form, for example.

The membrane would be clamped into an approved drain, and then the pan would be tested for leaks.

What I'm saying is, the shower would be built in the usual manner, and it's apparent your guy isn't aware of usual procedures.

flatfloor · 12-10-2003, 07:31 PM

This contractor, is he a sub to the GC or is he the GC?

bcesa · 12-10-2003, 08:43 PM

John, and flatfloor,

Thank you for the feedback. I printed out the Michael Byrne article on pans and gave it to him this morning. I think he might have glanced at it, and it is not here now that I have arrived back home from work so hopefully it is his homework tonite!....

tileguytodd appears to believe that the ultraset is OK, I saw it has an incredible spec, and will install over mortar, and I don't think the GC is going to use PVC because he was complaining that he didn't think he could find a piece that big (floor of shower is 45" x 60"). But I see your point about the drain tie-in. If he insists on the ultraset can he make it work?

flatfloor, the contractor is my general contractor. He is principally a carpenter, hence the plywood solution, I am sure. I am demolishing 2 bathrooms (circa 1965), expanding the house a bit, and constructing 3 bathrooms in the old plus new space. The master bath is the only custom pan (the other shower is preformed bottom, and the other bathroom has a tub). In a job like this, who typically installs the mortar pan? The plumber? Because, as I indicated, the subcontractor plumber is the one who recommended the ultraset to my GC, and I am sure my GC told him he planned to put it over the plywood.

The GC has indicated that he has installed 12 of the plywood/ultraset pans and some are over 10 years old and none have leaked, including the two in his house. That's what he says, anyway! But that's not enough of a track record for me! Should I bring in a mud man? Where do I find such folk in NJ? Yeller pages?

Bottom line is: the plywood is gone, it looks like he has a good preslope mortar bed, and will likely be installing the pan (ultraset or maybe PVC if he has a change of heart) tomorrow while I am out of town. Any recommendations on what directions I should leave for him? Be polite now! I could insist on the PVC, but I have already severely antagonized him today, and I don't want to continue the trend unless you all feel it is absolutely necessary, since he still has half the job to go. From what I get out of his comments, after the pan he will float another inch or so of mortar and install the tile.

Thank you again for all your help!

tileguytodd · 12-10-2003, 08:51 PM

I believe he can make this work if he treats it as a PVC liner.In other words trowel it up down and around everything and into the drain itself.then after it had dried apply the clamping assembly.Keep in mind that 30 mils is the minimum thickness and i believe 40 mils would be better.He will then need to do his final slope.This is a workable scenario for the product.A PVC or CPE Liner is considered the best approach,but i will say that i have done architecturally sped'd showers not much differant than what we are talking about here.differant product,but same principal behind it.The curb would need to be built and the membrane troweled completly up and over this and running it up the jamb a few inches wouldnt hurt either.Its a rather expensive way to go,but i see no problems with it not performing as advertised.

bcesa · 12-10-2003, 09:16 PM

tileguytodd,

Thanks again for your feedback. Your comment this morning led me to garner the strength to confront the GC, and insist that he remove the plywood pre-slope. Is it OK that he poured the mortar pre-slope directly over the plywood subfloor? Or do I need to make him rip it out again? Good thing I am a fast runner, I might live through this...

John Bridge · 12-10-2003, 09:18 PM

I'm afraid I'm sticking to my guns. I don't have faith in that to begin with, and I particularly don't have any faith in someone who doesn't have a clue. Sorry.

PVC comes in special order widths up to 8 or 10 feet, or you can seam two narrower pieces with cement they sell at Home Depot.

bcesa · 12-10-2003, 09:30 PM

John,

OK, I'm am going to try to "convince" him install PVC for the pan!

If he read the M. Byrne article I gave him he might actually do it correctly. Good thing I get to see his work each night.

I am still curious, who typically installs the mortar pan and tile in a job like mine (dining room extension, and reconstruction of 2 bathrooms and addition of a third bathroom). The plumber? A specialty person (what kind of trade would I be looking for?) A tiler?

All the other aspects of his work seem to be fine, but he really scared me on his approach to the shower pan.

Many thanks, again.

Sonnie Layne · 12-10-2003, 09:36 PM

agreed with JB.

Todd has a leg up, I've never used that method. I guess at one point there were guys saying "that plastic liner ain't gonna work... no way!!! " I'm willing to accept change, I gotta see it.

Todd's a good reference to these issues, but I'm quite comfortable with the ease, expense and security of the currently approved practices. Can his method be quoted paragraph and line in a document sanctioned by a recognized authority? I don't know.... that was a question.

If it's not sanctioned, he won't have a leg to stand on if it fails. And it'd be a bad thing if it were your leg that was stuck in the hole.