New Pan Installed

[mwinnick]

I'm redoing my shower. Everything was torn out and rebuilt and the plumber has reinstalled a liner for the pan. But, the liner was laid right over the concrete slab and fastened to the drain, and up the sides. My question is this. The plumber says I don't need a pre-slope mud bed put in first before the liner was laid down. Everything I've read say's you do. What's the right answer?

[GrumpyPlumber]

Either, as long as the finished surface has a slope.

[geniescience]

liner on top of slope. Plumbing code says so too, but that half-sentence is overlooked all the time.

With a liner laid flat, h2o molecules find their way down under the tiles and stay there for years on top of the flat liner. Moisture and warmth make mold grow.

With a liner laid on a slope, water slides over to the drain, slowly, and trickles out the weep holes that are in the sides of shoer drains. Or over the top of the liner if the drain is made for that kind of liner (membrane).

david

[jadnashua]

The only waterproof component of a tiled shower is the liner...THAT part needs to be sloped to meet code, but a lot of people don't follow that. Not doing it that way will lead to dissappointment in the long term. Doesn't mean it will leak, but any water trapped in the bed will just fester there and smell like a swamp after awhile.

[hj]

Many, many drains are installed without preslope, BUT the flange of the drain must be even with, or below, the floor level so water is not trapped by a lip when it reaches the drain.

[jadnashua]

That doesn't make it right...just lazy. It takes more time to do a preslope, liner, setting layer than it does to lay the liner on the floor. Concrete isn't waterproof, and water on a flat liner on the floor just doesn't drain very well...yes, the majority of it will go down the drain, but not all. You can't run a drain line with no slope, and you shouldn't run a liner without any and expect it to flow, either. New England's love of a copper pan flat on the floor is one example of resistance to change. Then, people wonder why the grout is wet and they have mildew or locker room smell problems.

[GrumpyPlumber]

Full copy of my states code for shower pan installation:
D. Shower Floors or Receptors.
1. Floors or receptors under shower compartments shall be laid on or be supported by a smooth and structurally sound base.
2. Floors under shower compartments, other than those laid directly on the ground surface or where prefabricated shower base receptors have been provided, shall be lined and made watertight by the provision of suitable shower pans of durable Product-approved materials.
3. Shower pans shall turn up on all sides at least above the finished threshold level.
4. Shower pans shall be securely fastened to the waste outlet at the seepage entrance making a watertight joint between the pan and the outlet.
5. Floor surfaces shall be constructed of smooth, non-corrosive, nonabsorbent, and waterproof materials.

Maybe one of you guys can see that sentence about sloping under the pan...I can't.

[markts30]

Ch4 of the UPC states:

When the construction of on-site built-up
shower receptors is permitted by the Authority
Having Jurisdiction, one of the following means shall
be employed:
(1) Shower receptors built directly on the
ground:
Shower receptors built directly on the ground
shall be watertight and shall be constructed
from approved type dense, nonabsorbent and
non-corrosive materials. Each such receptor
shall be adequately reinforced, shall be
provided with an approved flanged floor
drain designed to make a watertight joint in
the floor, and shall have smooth, impervious,
and durable surfaces.
(2) Shower receptors built above ground:
When shower receptors are built above
ground, the sub-floor and rough side of
walls to a height of not less than three (3)
inches (76 mm) above the top of the finished
dam or threshold shall be first lined with
sheet plastic,* lead,* or copper* or shall be
lined with other durable and watertight
materials.

All lining materials shall be pitched onequarter
(1/4) inch per foot (20.9 mm/m) to weep
holes in the sub-drain of a smooth and solidly
formed sub-base. All such lining materials shall
extend upward on the rough jambs of the
shower opening to a point no less than three (3)
inches (76 mm) above the top of the finished
dam or threshold and shall extend outward over
the top of the rough threshold and be turned
over and fastened on the outside face of both the
rough threshold and the jambs.

[geniescience]

stagnant water with a bit of organic material in it feeds a mold problem. Locker room smell. Damp grout near the drain. If you ever have to demolish it, the smell will be overpowering. That odor, to a lesser degree, is what you were breathing for years as the floor offgased mold mycotoxins. This is serious. It's not perfectionism to do it right the first time.

Some membranes are sheets. Some are trowelable, liquid membranes can you purchase in a paint can size. Many shower installers know all about this.

Cement-based sloped beds can be made on top of wood subfloors. That is called deck mud or sand mix. Also, presloped styrofoam pans are made, for the liner / membrane to be installed on top of. If you are on a slab, you can carve out the slope in the slab and that lowers the final floor height; you are not required to build upwards. Some people lower the joists and place a concrete sloped bed in the new space.

In all cases the paintable liner or the sheet liner goes on top of the new slope.

David

[GrumpyPlumber]

Another point in the differences of code from state to state...just wanted to be clear that I hadn't missed anything on my code.

[cwhyu2]

Our code never said any thing about sloping the sub floor .But we started
that practice 20 yrs ago.

[GrumpyPlumber]

Originally Posted by cwhyu2

Our code never said any thing about sloping the sub floor .But we started
that practice 20 yrs ago.

Same here, but most only slope above the pan...concrete / thinset is nonporous.
Though I agree with the arguments, lets face it...if the sub-floor isn't sturdy the thinset tends to crack over time...takes little or no more work to do it that way.
I just wanted to be clear that I wasn't mis-stating code.
Most copper pans I've done are commercial...which is usually on a concrete sub-floor over corrugated steele.

[cwhyu2]

WE didnt use thinset but quick setting cement that additives to prevent
cracking.And Icould set the pan an hour later. So I didnt have to come
back next day.Let the tile man have at it.