Q: When I recently visited the southern New Jersey coast, a fellow contractor told me that he made most of his shower pans out of fiberglass. Is this feasible to do on site?
A: Michael Byrne, a veteran tile installer and consultant, and the former moderator of JLC’s Ceramic Tile Forum, responds: Many different materials have been used to line wet areas over the centuries, including tar, used by ancient Egyptians, and lead sheets, used in Roman baths. Copper is still used today on occasion. But now these materials have been largely replaced with chlorinated polyethylene (CPE) or polyvinyl chloride (PVC) sheet material.
Fiberglass can also be used as an effective shower pan material. First, fiberglass cloth is fitted in the pan area, which then gets impregnated with resin to form a waterproof pan. But like every other type of pan material, the devil is in the details. Obviously, you want the pan to last as long as the structure where it is installed. But if the homeowner wants to remodel the bathroom—or if the pan was poorly fabricated and needs to be taken out—fiberglass can be difficult to remove from studs, backing, and subflooring.
Like any other shower-pan material, fiberglass resin and cloth must be installed over a subfloor with a 1/4-inch-per-foot slope to the drain. Just as important is the resin itself. Most are water- and chemical-resistant, but some may not be: If fiberglass is specified for your install, a boat shop is probably the best source for resin and cloth. Crack prevention is another reason to use fiberglass materials formulated for nautical use, because boat structures are constantly bending, deflecting, and twisting. Building structures also move about, and fiberglass resins that cure rock-hard may corner-crack. Harder resins may also develop cracks around drain housings that are not adequately supported.
Fiberglass is a good choice for tile showers or sunken tubs that are curved or irregularly shaped. Regardless of the shape of the installation, however, shower pans made from fiberglass resin and cloth need to be properly supported. For most applications, this means installing blocking between studs that extends at least 9 inches above the sloped subfloor.
When it’s time to hang metal reinforcing mesh for the overlying mortar bed, fiberglass actually excels over other materials. As the mesh laps over the fiberglass pan, it can be securely attached to the pan with dabs of resin.
One problem when working with fiberglass is keeping resin off the bolts where the pan attaches to the drain housing. I’ve found that the best way to keep bolt threads clean is to screw the bolts at least two full turns into the housing and then wrap the entire protruding bolt with Teflon tape.
The curb is also an area that requires special attention when making a shower pan out of fiberglass. Make sure the fiberglass resin and cloth cover all three sides of the shower curb and lap up the jambs or sides of the shower opening.
One final area of concern is the interface between the outside face of the curb and the bathroom subfloor. Protecting the bathroom subflooring with resin and cloth is one option, but I don’t recommend it. Instead, I’d use a sheet or liquid-applied membrane made for use with tile. Just be sure to join the two surfaces with a sealant that is compatible with whatever membrane you use as well as the cured fiberglass surface.
