A CONCERNED homeowner wrote:
“My husband and I had our house built eight years ago. We developed a leak in our shower stall and the plumber that we had come by — he is not the one who did the work on the house — told us that there must have been no vinyl pan put under the tile work and above the concrete slab. When they had to (alas) break the tiles, indeed, there was no vinyl pan.
“Why is it actually called a ‘pan’ when it is nothing more than waterproof vinyl cut to fit?
“So far the plumber has charged $485 and the tile work is going to cost $1,100.
“Can I ask you, does every shower have to have a vinyl pan or can the shower be built without it?”
Almost all ceramic tile bathing environments require a “pan” liner. We’ve always called it a pan because it resembles one after the sides are formed. Prior to vinyl, we used 4-lb. sheet lead (it weighs 4 lb. per sq. ft., hence its name) and that could be quite heavy when doing a large walk-in shower pan. Copper and hot mopping were also used, but lead became popular due to its malleability and faster installation time.
We would form up the lead pan in the garage or other suitable spot that offered a smooth flat surface without sharp objects and bend the lead sheeting over a 2-by-6 to shape the edges. Corners were folded and overlapped to keep all edges along the top. Once formed, we would carry the pan (appropriate grunting helped) through the maze of rooms and hallways to the bathroom and often found it necessary to gently fold it over onto itself to negotiate tight corners.
Once in place, the wooden mallet we’d used to form the shape was again employed to locate the drain opening by pounding the lead sheet to create an impression of the shower drain. Careful trimming created the opening for attaching the capture ring or flange, which would create the watertight seal once fastened. The adjustable shower drain was threaded into the opening and pea gravel was mounded up at the weep-hole openings just prior to installing the “deck mud,” which is a mix of mortar and sand on a 1:4 or 1:5 ratio.
Not much has changed regarding overall installation of a shower pan. The substitution of vinyl for lead reduced labor time due to the ease with which vinyl can be formed into shape. Original shower drains with bolt-down flanges could be reused, but we quickly discovered that the screw-down flanges caused the vinyl to bunch up, squeeze out or become too distorted for use and a new drain had to be installed. Although water can be used to mix the deck mud, latex additives make a stronger mix with much improved compressibility. (Deck mud should be only wetted enough to allow for it to hold its shape.)
If the pan is installed over a plywood sub floor, a layer of 15-lb. tarpaper is put down first followed by expanded galvanized metal lath stapled down over it. The first tapered layer of deck mud is then applied to the lath. Once cured, typically overnight, rough spots must be ground smooth and plywood strips installed for backing between the studs to support the vertical portion of the pan liner walls. If the installation is over a concrete floor, the first tapered layer of deck mud can be installed with or without a crack isolation membrane, depending on the stability of the original floor.
The sheet vinyl is then installed over the first tapered layer of deck mud, wrapped up the sidewalls to a minimum of 3 in. above the intended finished floor height and wrapped over the threshold. Inside corners are easily folded and contact cement permits almost immediate bonding of the corners. Outside corners require greater skill!
No nails or other fasteners are to be used, other than around the top perimeter and the outside of the threshold, or eventual leaks will develop at the penetrations. The concrete backer board is installed over the studs to within 1/2 in. of the liner’s base and traps the vinyl between itself and the studs.
Wire lath is wrapped over the threshold and deck mud applied to a minimum thickness of 1 in. Following this, a concrete base is poured (typically 1 1/2-in. thick) over the vinyl and tapered to the drain. This newly poured base captures the concrete board and deck mud applied over the threshold. Ceramic tile work follows for the finished shower.
To every rule, however, there are exceptions.
I’ve had general contractors who refused to install pan liners when installing ceramic tile over concrete slabs. I’ve also seen ceramic tile contractors follow this same procedure in order to shave costs.
There is an application that uses a liquid sealer for the concrete-meets-wall areas that can be brushed on, which is said to provide adequate waterproofing by those who favor its use.
Our policy is to install the pan as outlined above, which I feel offers the best long-term protection. The added up-front costs far outweigh the costs for repairs to both home and reputation. The old saw, “An ounce of prevention is worth a pound of cure,” applies!
Dave Yates owns F.W. Behler Inc., a contracting company in York, Pa. He can be reached by phone at 717/843-4920 or by e-mail at [email protected].
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