Replies

1. 
   Guest_ | May 18, 1999 02:12am | #1

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   For setting plumbing fixtures as you describe, I use a 4:1 mix of sand and common cement. You'll want an aggregate in the mix, I use pea gravel. Mix it kind of stiff, place the mortar and set your fixture. In the case of a tub, fill with water for weight.

   Of course, you have made all your calcs and measurements "dry" and beforehand. Leave all plumbing lines disconnected from fixture until mortar sets up. (At least until the next day)

   For an acrylic shower receptor, omit the aggregate. I use the same mix as mentioned above, but mix just a tad loose. With a shower pan, you can--and need to--slide and shake the pan to settle it into final position.

   It helps if you have drawn registration/level lines on the walls and fixture rim. Again, I suggest you "dry fit" everything beforehand. It's misery when you find you have a perfect fit 'cept you are 1/2" too high.

1. 
   Guest_ | May 20, 1999 03:44pm | #2

   *Rich,Had a laugh once. Mate of mine deciced he was going to use expanding foam to support the bath. Put it in and came back to find the bath pushed up out of it's frame.

1. 
   Guest_ | May 21, 1999 07:19am | #3

   *Mark,, yeah, what a laugh. I also heard about a guy doing that. hehe I did see, with my own eyes, the results of using too much expanding foam between decks on a day sailer. The guy wanted to add some flotation below the false bottom, but didn't know enough to leave vent holes or how to proportion. Next thing--BLAMO--the sound of wood splitting and a curious hump in the deck. The best laid plans...

1. 
   Guest_ | May 21, 1999 12:41pm | #4

   *..at least it wouldn't sink in a hurry

2. 
   todd_pickering | May 22, 1999 07:45am | #5

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   I do a number of bath remodels. Its cheap insurance to keep the tub from flexing and get rid of the hollow fiberglass sound. I use one bag of regular old anybody's Mortar Mix -- it doesn't have the bigger aggregate that concrete mix does. Get everything ready to hook up perfectly. Level it and mark all the edges so it goes back in exactly the same spot. For tubs I usually draw a rough outline on the subfloor so I dont waste mortar in voids. Keep it fairly stiff so it doesnt slump too far on you, then set it in and check your marks.

3. 
   Guest_ | May 25, 1999 05:58am | #6

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   Sorry about going off on a tangent, but, well...

   Back in college, we were doing foam in an organic chem lab. We were to vary formulations, measure amount of expansion, temp, density, etc, all that goody school stuff. All work was done behind a ventilation hood for off-gassing, etc. Most of us had our own keys to the chem lab so we could do work after hours.

   One morning we were all told to report to the lab. Upon arrival, one of the hoods was completely filled with foam. There was nothing but foam behind the viewing window which was about 3'wide by 3' high, the window was also distorted due to the heat given off by the reaction. Nobody fessed up to the dirty deed.

   When they eventually took the front window out and chopped the foam out, the culprit was unmasked. Her research notebook was found encased in the foam. Apparently, she had trouble differentiating milliliters from liters, she was only off by a factor of 1000!

4. 
   Jackson_Sadler | Jun 03, 1999 06:54pm | #7

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   I have used expanding polyurethane foam successfully under acrylic tubs, creating a solid, sound-muffling base with wonderful insulating properties (a tub full of hot water will stay hot much longer). As with many materials, polyurethane expanding foam must be used carefully. If injected into cavities carefully, in proper amounts, and cured thoroughly between applications, large cavities can be filled without bulging or tub movement. (Wear some disposable latex gloves coated with some kind of oil)

5. 
   Guest_ | Jun 05, 1999 05:46am | #8

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   We've set quite a few of these shower pans using Structolite (perlited gypsum plaster.) The stuff is nice to use because it's lightweight, and once under the pan, you can use your weight to kind of squish it into place. No aggregate to worry about, no shrinkage, no expanding foam. (Stuff works great under fiberglass whirlpool tubs, too.)

1. 
   Guest_ | Jun 20, 1999 04:51pm | #9

   *For setting the fibreglass tubs in my new house the plumber used plain old sheetrock mud,pouring a bucketfull under each tub and standing in the tub to settle it. I have had no problems that I know of for two years now. Was it OK to use this stuff?

1. 
   Guest_ | Jun 21, 1999 04:42am | #10

   *Only things I can think of as problems in using 'rock mud are: the shrinkage of the mud as it cures, allowing some possibility of movement of the fixture and the higher cost of the mud. Then again, I have never used it for this purpose so I could be wrong.

6. 
   willi_ | Jun 21, 1999 01:06pm | #11

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   if it's a thin acrylic or fiberglass tub, i would stay with mortar mix, i think regular drywall mud has the density of chalk when dry, and Rich's remark of shrinkage [i.e. cracking]is an important factor, if it's cast iron tub then maybe, but why take chances. Good luck!

7. 
   Guest_ | Jun 27, 1999 07:01am | #12

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   Ditto on the Structolite. I've never seen anyone use anything else.

   RM

8. 
   L.I._Phil | Jun 27, 1999 07:01am | #13

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   What is the "mortar-mix" made of that should be put under an acrylic tub/shower to support the base? Brand name suggestions?

   Any tips for doing this job (like putting plastic sheet below and above the mortar)?

   Phil