Shower Pan Question for Hot Mop Experts

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Pete Billow

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I'm a little concerned with the approach my contactor is using to prep to hot mop a shower pan floor (yes I'm in SoCal). I'm hoping some knows if his way is considered acceptable and is to code.
His plan to prep for hot mop (floor is concrete slab / shower size is 3' x 5' :
- lay down a couple of layers of asphalt shingles along the outside of the 3' x 5' shower pan, with the outside edge being two or three layers, and then reducing to one or two layers, and finally to no layers closer to the drain.
- I believe he will then lay down a layer of felt/tar paper, and then hot mop directly over that.
- He will then further slope and smooth things with the mortar bed that the tile will be installed onto.
My thoughts on how to do it:
- Pre-slope a bed made from mortar mix cement installed on the slab
- hot mop on the pre-sloped mortar bed
- install the mortar bed for the tile over the hot mop.

is either one correct? Does his method meet code (I've never heard of doing it that way)?

Thanks for any and all answers.
 

Plumber's Friend

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I had never heard of a hot mop shower, but I googled it and got lots of results. I've built a mortar bed directly on the slab and used a mop on sealer like that red stuff at Home Depot, and I've used Ditra uncoupling membrane. I like the Ditra.

Are earthquakes an issue? How does asphalt fare when the earth moves?

I hope I'm not violating any rules, but there is a wealth of tile information at JohnBridge.com.
 

Dj2

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Your shower pan guy is correct.

To calm your nerves, get a second estimate from another shower pan guy.
 

Cool Blue Harley

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From the California Plumbing Code section 408.7. "Lining for Showers and Receptors"

Nonmetallic shower subpans or linings shall be permitted to be built up on the job site of not less than three layers of standard grade 15 pound (6.8 kg) asphalt-impregnated roofing felt. The bottom layer shall be fitted to the formed subbase and each succeeding layer thoroughly hot-mopped to that below.

As far as the shingles go it also states "Nonmetallic shower subpans or linings shall be permitted to consist of multiplayer of other approved equivalent materials suitably reinforced and carefully fitted in place on the job site."

Hope this helps. The plumbing code is subject to interpretation.
 

Cool Blue Harley

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Additionally, although I do not inspect as many hot mop shower pans these days, given the popularity of new products available with their ease of installation, hot mop pans are perfectly acceptable and I would be comfortable with one in my own home.
 

Jadnashua

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The hot mop is your liner, and it MUST be smooth and be sloped to the drain at least 1/4"/foot, otherwise, it will allow moisture to accumulate in the bird baths. FWIW, the setting bed should be smooth, but maybe one of the harder things on a hot mopped shower is to keep the weep holes of the drain clear.

Personally, I much prefer a more modern, surface applied membrane, then there's almost nothing inside of the shower that can accumulate moisture and the WHOLE thing is waterproof, not just the pan liner.

The mudbed beneath the tile WILL get wet and must be properly sloped and the weep holes Must remain open. Tile is NOT waterproof, but it is the decorative, wear surface.
 

Pete Billow

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Thanks to all of you for your replies. It sounds like the way he is going to do it probably meets code sine there's ambiguity in the code. I think I'm going to ask him to do a sloped mortar/cement bed under the hot mop since using stacked asphalt shingles doesn't seem like it would be solid enough and there could be areas where water could pool.
 

CountryBumkin

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Thanks to all of you for your replies. It sounds like the way he is going to do it probably meets code sine there's ambiguity in the code. I think I'm going to ask him to do a sloped mortar/cement bed under the hot mop since using stacked asphalt shingles doesn't seem like it would be solid enough and there could be areas where water could pool.

Building code is the "minimum" requirement. There are superior methods now that exceed the minimum/code, but will probably cost a little more. It's your money. Good luck.
 
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