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g-stein 02-27-2002 08:03 PM

Good evening. I am the proud owner of a 5 year old home built by a "Florida Master Builder". My task this week is to rebuild the masterfully built bathroom. This brings me to a couple of questions. I hope I am not being greedy by asking multiple questions.

1: When he installed the shower pan he simply "V" notched the corner of the PVC liner then draped one edge over the curb and the other edge up the side wall This left a leak inside the shower where the curb meets the shower wall. Needless to say, when I removed the tile on the curb the wood came out in small, soft rotten pieces. Of course, the walls are constructed with tile over green plasterboard which is now green mush underneath the tile. My question is this. What is the best method of rebuilding the shower walls to give a 25 year life? I am considering cement backerboard but I am wondering if a concrete mud wall would be worth the extra efort. I have worked with stucco so the mudding shouldn't be a problem. FYI, we will be selling in 4 years but I would like to make the shower last as long as the house.

2: I am considering replacing the floor in the bathroom (not the shower) with a tile called "aglo simplex" by a company called Santa Margherita. This tile is marble chunks embedded in resin then sliced and polished. I picked this tile because it gives the look of marble but has better traction when wet. Has anybody used this tile before? I am concerned about durability and the ability to polish the tile after it is scratched. The tile will have a 1/16" groute line and the floor will be leveled with self leveling compound to minimize unevenness.

3: This tile is only 5/16" thick and soft so I assume cracks in the concrete slab will telegraph through. My problem is that I would like to install electric heating wire (flextherm) under the tile to keep my lovely wifes tootsies warm. Does anybody have any suggestions for a decoupling membrane that will not impede heat flow from the warming wire? I anticipate cutting slots in the slab for the heating wire then about 1/16" of self leveling compound to cover the wires. Keep in mind that a Florida "Master Builder" built this house so the slab is thin and is showing more crack than the redneck who poured it.

Anyhow, thanks in advance. George Stein.

Rob Z 02-27-2002 08:29 PM

Hi George

Mud walls will certainly give the life span that you are looking for. Another option is to use cement board, and covering it with either a liquid applied membrane or a sheet membrane. The membrane I use most often is Laticrete 9235. I have also used Schluter Kerdi and Noble TS. There are many other quality products that some of the regulars here can recommend.

Our benevolant host, John Bridge, has a great book detailing how to float mud on walls. I have also gotten a lot of good information from Michael Byrne's "Walls" video.

I am not familiar with the tile that you are considering. Let's see if one of the others has used it.

I would suggest using NuHeat for the heating mat. The mat that the wires are embedded in may well offer some crack isolation properties. If not, I would use Schluter Ditra over the heating mat.

Bud Cline 02-27-2002 08:57 PM

I only read the last paragraph and my comment is: DITRA

g-stein 02-27-2002 09:34 PM

Rob: I am thinking the cement backerboard route will be adequate if done right since this house will probably fall down before the backerboard fails, but I didn't realize a membrane should be applied over the backerboard. Is the membrane used to stop moisture? Would the use of this membrane eliminate the need for a vapor barrier?

I have already purchased heating wire from Flextherm which is 1/16" dia. I think I will try to scare up some DITRA and test its heat transmission ability. Incidentally, I have been told by some local tile folks that using a good latex modified thinset over self leveling compound and combed with a 3/8 X 1/4 trowel would eliminate the need for a membrane on a concrete slab. I tend to not believe them but I thought I would ask anyway. Thanks again

g-stein 03-02-2002 07:12 AM

Sand layer over pan liner
I am not sure if anyone is lurking here on the weekend but I think I will ask a question anyway. I have created a sloping mud subfloor in my new shower and am about to install the PVC pan liner and mud floor. I was staring at the job this morning and had a rare spasm of inspiration. It seems to me that it would be a good idea to put a thin layer (1/8"?) of clean sand on top of the pan liner before installing the lath and mud floor. Wouldn't that help the pan to drain? Any comments? I am using quickrete topping mix which is what was recommended to me for the shower floor. Thanks. George

John Bridge 03-02-2002 08:29 AM

Hi George, Welcome aboard.

I would not use the loose sand under the pan. Your pre-slope mortar is all that is needed.

Robert Villa 03-02-2002 09:53 AM

Sand Goes On Top of the Pan, Right?
John, I think you misunderstood the question, He wants to know if he can put sand on top of the pan, below the setting bed.

I am not qualified to answer the question, but am qualified to re-ask it.

I would assume that the purpose of the sand would be to elevate the setting bed and help it drain, yes? Like an extenstion of the pea gravel one places on top of the weep holes. So whaddya think?

The other question I have is"

What is the statute of limitations for a lawsuit against a "Florida Master Builder" in Florida. Here in SoCal it is 10 years.

g-stein 03-02-2002 10:43 AM

Sand and Stuff
Actually, I am going to see a lawyer on Monday to ask the question about builder responsibility, but not necessarily for the shower. The shower only cost a few days and a few six packs, other problems are not so easily fixed. Anyhow, I re-thought and I imagine there is the possibility of the sand washing down the drain if water should get underneath. Perhaps I should re-ask the question, Is there a standard way to improve drainage under the mortar bed? I am probably just stressing about a non-issue. The builder caulked (Yes, Silicone Caulked) the weep holes shut and moisture destroyed the wood around the shower and disolved the bottom foot of green sheetrock, so the drainage issue is on my mind. George

John Bridge 03-02-2002 01:03 PM

Yes, I did mis-read the question, but my answer remains the same. I think George answered his own question. The sand could possibly plug the weepholes. Pea gravel would be better, but nothing is needed so long as the pre-sloping is done correctly.

Builders are builders no matter where you go. They all belong to the same fraternity. They are mostly bottom-line guys (and gals) who don't know a lot about building a home. They depend on sub-contractors who in many cases don't know any more than the builders.

I simply quit working on production housing years ago. Nobody wants to pay for quality workmanship.

stullis 03-03-2002 01:14 AM

Using the 3/8 notch is not a replacement for the membrane as you have summized.

Use of the Ditra over the Flex-Therm is a good idea. Also use a high quality thinset when using an in-floor heat system. Now, you are in Florida right, why the infloor heat?

g-stein 03-03-2002 03:27 AM

3/8 Notch
Concrete floors can be cold at night, the floor heater is a low wattage unit to keep my wife's tootsies warm. I am using a white "flexible" latex thinset specified for marble. The coils will be buried in the self leveling compound then the tiles will go on with a 1/4-1/4 notch over the crack isolation membrane. I think the isolation barrier is especially important with heating coils because repairing a broken tile would probably damage the heating coil. The barrier reduces the possibility of a break and provides protection if a repair is needed.

Incidentally, I finished my "unanticipated" shower rebuild today (except for the tile, my wife gets to pick that out next week). It is durrock with a mud floor. This site was incredibly helpful. The shower pan "model" at Lowes and the instructions that came with the PVC liner showed no sloping subfloor and even suggested green sheetrock extending down to the bottom of the liner. It is amazing the amount of mis-information out there. Browsing through this forum (and others) was very helpful in pointing out some of the pitfalls and bad advice that abounds everywhere. Thanks again. George.

John Bridge 03-03-2002 09:13 AM

I am once again reminded of the number of engineers we have attracted to this site who are literate and can speak English.

I think we must have about twenty. That should be all of them, shouldn't it? ;)

Rob Z 03-03-2002 09:49 AM


I just read a post of your from several days ago. Yes , the use of a liquid or sheet membrane on the OUTSIDE of the substrate in the shower will eliminate the need for a vapor barrier behind the substrate. If you use Durock or one of the other cement boards, then be sure to caulk the bottom of the panel. I use Noblesealant 150, but silicone should work as well.

I spoke with the folks at Schluter about Ditra going over heating mats (I have a job coming up where Ditra is going over a NuHeat mat), and they say their testing at their lab didn't find any appreciable loss of heat due to the Ditra being on top.

If you want to talk engineering specifics, you can contact Peter Nielsen, Technical Director at Schluter, for info. He is very helpful. http://www.schluter.com

Next time I have an electrical science Q, I'm coming to see you. The circuits Q's in physics used to kill me. :(

g-stein 03-03-2002 11:05 AM

Hmmm. I hope the engineer thing isn't too obvious.

Anyhow, I am about to start sticking down the heating wire, which is all I was trying to do when the shower curb fell apart. This heating wire uses zinc plated steel looms which stick to the concrete and can be embedded in thinset or SLC. I wonder if steel embedded inside of SLC will rust?
I am pondering using dabs of hotglue to stick the wire down rather than the looms for that reason since wire floats in cement and I will have to stick down the wire every foot or so anyway. Any thoughts? Incidentally, I picked wire rather than mat because I wanted to run a stretch of wire under the (fake) marble thresholds so they will be warm.

I didn't think of caulking along the bottom of the durrock. My resoning was that the durrock won't rot away and any water that wicks up between the durrock and the liner will drain away into the liner. I hope the next owner won't be cussing out the nitwit who forgot to caulk the bottom of the shower :/
Thanks again, George

cory carlson 03-04-2002 07:22 AM

Nice job George. Way to promote us "damn" engineers. :D

John, in my brief travels I have encounter roughly two kinds of engineers. Those that want answers and those that think they already have them. George is a good example of the former. Again, nice job George, and if you are ever in need of some engineering company I will sacrifice and come down to Fla to visit you. :) *Man it's getting cold up here*

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