Help with Shower Bed.

[tmy23]

Thanks in advance for any help.

I ready to begin the shower pan for a bathroom conversion of what was a 2nd floor nursery in a 132 year old Victorian. The shower is 4' x 5' with a linear drain at the end as I didn't want to drill the floor joists for waste line. My question is about pan construction and weight.

I was planning on the standard 2 layer bed, building paper, metal lathe, slope mud layer (1/4" per ft), membrane, top mud layer than tile.

If I've fully understood what I've read, the minimum thickness of the slope layer should be at least 1" at the drain end. Over a 5' run, this layer will be 2.25 at the high side. Again from what I've read, the "finish" layer should be at least 1.5" uniform, thus the total thickness of the bed will range from 2.5" at the drain end and 3.75" at the high end.

If I use a rough average of 3" for the average thickness of the pan, it weighs 37.5lbs/sqft, or over 700 lbs for the 20sqft! Aren't most floors rates 40lb sqft live load? I haven't yet put water or people in? J

Something seems amiss? I hope I'm reading the minimum thickness of the two layers wrong? With the lathe affixed to the subfloor, it seems ¼" mud at the thin end, or just enough to keep the lathe from penetrating the membrane would be enough to pour another 1.5' finish layer?

I've been pricing Kerdi and it's no bargain, but I guess I'd go that way it if there are no alternatives?

Does anyone have a single layer alternative?

I visited a site where a guy swore by a single layer mud bed, over lathe, sealed in redguard, taped and then up the concrete board walls? This eliminates one of the layers?

Again, I deeply appreciate any help. Hopefully I am over thinking (engineering) this thing….. J

 

[Jadnashua]

There are other sheet membranes - Laticrete's Hydroban sheet, NOble also has several, then, don't go by suggested retail...you can find the stuff discounted if you look around. If you haven't priced linear drains, be prepared for a shock...they're not cheap! The least expensive version will be one that you tile, verses a finished metal grate version.

One reason to consider a surface applied membrane, at least IMHO, is the total weight. Yes, a typical residence is designed for a 50#/sq foot total load in most cases. Without measuring the joist size/length/spacing, you cannot determine what the deflection rating is. Hard to tell on an old house.

A sheet membrane will allow a single, sloped mudbed, cutting your overall weight down considerably. Now, there are millions of homes with them in there now, and they haven't fallen down! If you want to save yet some more weight, Schluter, Laticrete, Mapei, and probably a few others make preformed foam pans for use with their membranes. A mudbed is much less expensive unless you're paying labor, and works with a membrane as well. Especially on an older house, the foam pans may require some leveling of the subflooring before use, and a mudbed is much more forgiving since it is built in place, and can overcome all of those issues.

Check out www.johnbridge.com where they specialize on all things tiled, with lots of pros and a wealth of knowledge to help you along. Terry's site works great for figuring out the plumbing issues, or electrical, etc., but is light on tile...lots more pros over there to help you along.

 

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[Cacher_Chick]

700 lbs is not much more than a cast iron bathtub filled with water...