All fiberglass surfaces have a gel-coat finish that chips and cracks easily. Fiberglass shower enclosures generally come from the manufacturer with no openings for faucets or showerheads. In most cases, drilling the openings is left to the homeowner or plumber doing the final installation. Plumbing fixtures typically come with a fixture template to transfer the required drilled hole openings to the fiberglass surface. Redundant measuring is perhaps the biggest key element in correctly drilling fiberglass showers.
Things You'll Need
Plumbing fixture templates
Personal protective equipment
1/8-inch drill bit
Hole saw with 1/4-inch center drill
Vacuum cleaner (optional)
Lay old cardboard on the floor of the shower enclosure to protect the gel-coat surface from footwear or tool scratches.
Identify a rough area of the plumbing fixture location, using the plumbing fixture template. Mark a rough square area on the shower wall by making light marks with the pencil and tape measure. Fill in the area with overlapping pieces of masking tape. The masking tape aids in correct identification of the hole's location and prevents chipping to the gel-coat surface.
Measure the location of the plumbing holes, using the tape measure and template. Mark the center of the holes with a black marker. Check those measurements several times before proceeding.
Install the 1/8-inch drill bit into the chuck of the drill motor. Tighten the drill bit into the chuck. Hold the drill motor and bit perpendicular to the shower wall surface.
Drill the pilot hole. Do not force the bit. Allow the tool to drill the hole for you. Drill all of the center pilot holes first.
Remove the 1/8-inch drill bit. Install the correct size of hole saw into the chuck of the drill motor. The size of the hole saw will be the exact same size as shown on the plumbing fixture template layout from the fixture manufacturer.
Hold the center 1/4-inch drill bit of the hole saw perpendicular to the shower wall over the previously drilled pilot holes. Start the drill and gently push forward, allowing the drill bit to cut into the material. Keep an even forward pressure when the hole saw engages the fiberglass surface. If possible, have someone hold the suction end of a vacuum cleaner near the hole saw while cutting. This will reduce the amount of material in the air.
Be sure to wear personal protective equipment when working with fiberglass. This will include eye and protection and an approved dust mask.
Exercise extreme caution when working inside the shower enclosure. Do not drop or hit the enclosure with metal-edged tools. The hard edges of the tools can permanently dent the gel-coat surface.