How to Replace a Fiberglass Door Glass With Lexan

Remove the trim surrounding the glass holding it in place within the door. This frame is held in place by small screws, but the screw heads might be covered with small plastic plugs, putty or even caulk. Dig any covering off the screws with a small, flat-head screwdriver. Remove the screws. Work carefully to avoid damaging the trim or breaking the current glass pane. Save the trim to reinstall.

Slip a utility knife blade between the window frame and door. Slide the knife around the window perimeter to break any seal or cut loose any caulk or adhesive. Carefully pull the interior frame free while a helper supports the glass from the door exterior. Pop the glass free with gentle pressure applied to a window corner.

Clean any adhesive or caulk from the door glass opening. Use a knife to scrape away the material or wipe with mineral spirits or a similar solvent to remove. Repeat with the removed trim.

Run a bead of glazing compound around the edge of the window opening to replace the old seal. Use a generous but not excessive amount to avoid large beads squeezing out onto the window during replacement.

Insert a piece of Lexan polycarbonate into the glass opening. Position the Lexan with the coated side, if indicated, facing outward. Purchase the Lexan in a cut-to-fit size or cut it to fit yourself. Measure and mark the Lexan to 1/8 inch less than the opening, both height and widthwise, or to the same precise measurement as the old glass.

Use a power saw to cut. Ensure your blade is sharp, the Lexan is clamped in place and the blade is at full speed before biting into the Lexan to prevent the plastic from twisting and tearing at the edges.

Press the Lexan firmly in place. Run another bead of glazing compound around the perimeter of the Lexan. Adjust the amount you apply according to the previous bead between the outer door and the Lexan. If you see excessive amounts squeezed out, use less. Otherwise, use about the same amount.

Replace the inner door trim framing the window. Press the trim in place securely and attach with the screws previously removed. Cover the screw heads with plastic caps, if applicable, or cover with caulking.

Remove any masking, decals or similar objects from the Lexan's surface. Wipe away excess glazing on both sides of the door. Clean with mineral spirits or a similar solvent to remove stubborn glazing.