Can anyone tell me about hot mop shower construction?

jrueterJune 13, 2014

I have learned so much from the experts on this thread. Mongoct and BillV and lots of others have posted great "tutorials" on how showers should be built.

Here in California hot mop is the standard for shower construction. Can anyone fill me in on the details of how the shower floor should be constructed so I know what questions to ask and what to look for to (hopefully) avoid problems during install?

(I have vetted the GC, seen his work and have references from two neighbors and a friend who have used him - I am just trying to be thorough)

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Babka NorCal 9b

I live in CA...Sunnyvale. Back in the late 70's, when we redid our shower, we did a hot mop. Absolutely no leaks over 40 years. They applied 3 layers of tar paper and tar over each. Probably 3/4" thick. Last year when we remodeled the bathroom they did Kerdi. So far no leaks. Technology.

My suggestion would be to go with what your contractor is familiar with, if you like that you can work with and who listens to you. The Kerdi is thinner, so the curb entrance to our shower is only 3" off the floor, unlike the 6" curb we formerly had. MUCH easier to step into the shower.

Good for you to do the research to see what works for you.


    Bookmark   June 13, 2014 at 10:52PM
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Thanks, Babka.

Any pros out there with hotmop knowledge? TIA

    Bookmark   June 17, 2014 at 10:10AM
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Also in CA and the 13 year old showers that came with the house were hotmoped and have had no leaks. Did an addition 2 years ago with a new shower and that was also hotmoped. I'm just remodeling the master bath and the large shower was just hotmoped last week. The Ladies that did the work have been in business for 20+ years! I used 2 different GCs with very good reputations and this is what they are used to working with. It does seem to be a very CA thing!

    Bookmark   June 17, 2014 at 8:09PM
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You'll fare well by heading over to the John Bridge Tile forum where Bill and many CA tile experts hang out.

    Bookmark   June 17, 2014 at 8:19PM
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Great advice, Houston! Thanks!

    Bookmark   June 17, 2014 at 10:24PM
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Hot mop is definitely a left coast thang. Seeing as I live on the correct coast, it's not my area of expertise, so I have no advise to offer.

As has been mentioned, there are folks that pull a trailer of tar and hot mop all day long. They're good at what they do.

    Bookmark   June 17, 2014 at 10:40PM
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P2709.2.3 Hot-mopping. Shower receptors lined by hot mopping shall be built-up with not less than three layers of standard grade Type 15 asphalt-impregnated roofing felt. The bottom layer shall be fitted to the formed subbase and each succeeding layer thoroughly hot-mopped to that below. All corners shall be carefully fitted and shall be made strong and water tight by folding or lapping, and each corner shall be reinforced with suitable webbing hot-mopped in place. All folds, laps and reinforcing webbing shall extend at least 4 inches (102 mm) in all directions from the corner and all webbing shall be of approved type and mesh, producing a tensile strength of not less than 50 pounds per inch (893 kg/m) in either direction.

    Bookmark   June 18, 2014 at 11:08AM
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In our previous home, our new shower was hot-mopped (yes, California). In our current condo, our contractor used one of the newer products (I think Hydroban but I'm not really certain). It seems like the latter would be easier, although the former works just fine (we never had a leak in the shower before or after remodeling in the 26 years we lived in that house).

    Bookmark   June 18, 2014 at 1:36PM
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Understand that Hot Mop is pretty much "Old School" technology. About the only area that still uses it is in Cali. Make no mistake, it works well when done correctly, but Cali is quite a bit behind the times as far as 21st Century Technology goes. There are far better methods around now, but hey, you pays your money and you takes your chances.......

    Bookmark   June 18, 2014 at 8:05PM
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I'll take me some "Old School" technology any day. Give me something that's tried and true and works well and I see no reason to mess with it. I'd rather hire someone who knew the old school method through and through than someone who had just learned a "new" method. Personally, I long for more "old school" technology as I pretty much equate that with a quality product that lasted a long time.

    Bookmark   June 18, 2014 at 10:38PM
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StoneTech - thanks for the details on construction and materials - very helpful

I guess like anything else, each method can be done well, or done poorly. The GC has been in business a long time with very happy clients, so I am pretty sure they know what they are doing. Like jellytoast said, I would rather go with someone proficient at a tried and true method than someone less well versed in the new method.

    Bookmark   June 19, 2014 at 10:05AM
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