How to Repair Large Hole in Fiberglass Tub? Because you purchased a fibreglass bathtub because it was lightweight and inexpensive, it was probably realistic to predict at the time that you would require fibreglass bathtub repair. To be fair this all-purpose is fairly durable, fibre-reinforced plastic material, and a fibreglass bathtub can last as long as one constructed of heavier materials with proper support and care.
Fibreglass, on the other hand, does not age as well as cast iron, steel, or even acrylic bathtubs, and it can become brittle and prone to cracking and other damage over time.
Things You’ll Require
- Acetone
- Painters’ tape
- Soft cloth
- Electric buffer
- Auto polish
- Drill
- Epoxy filler
- Utility knife
- Cardboard
- Hardener
- Fibreglass cloth
- Polishing compound
- High-density spray foam
- 400- and 600-grit wet/dry sandpaper
- Waterproof spray enamel (if needed)
- 1/4-inch wood-boring bit
- Applicator or plastic putty knife
How to Repair Large Hole in Fiberglass Tub?
Here is the step-by-step guide to Repair Large Holes in Fiberglass Tubs in 2023:

Step #1. Clean the Repaired Area
To remove grease, oils, and soap residue, use alcohol or acetone to clean the area around the crack or hole. You can use the cleaning wipes or pads that came with your bathtub repair kit.
Step #2. Use Painter’s Tape
Wrap a double row of painters’ tape around the area to be repaired. Painters’ tape is preferable to adhesive tape or duct tape because it is easier to remove and leaves no residue. To enable for a cleaner repair, leave about 1 inch of the bathtub surface exposed on all sides of the damaged region.
If you’re mending a huge hole, consider including fibreglass fabric in the repair epoxy. The fabric should be broad enough to overhang the sides of the hole by about 1/2 inch, and a larger area should be taped off to enable sanding the edges simpler.
Step #3. Drill Stop-Drill Holes as well as Reinforce the Fiberglass
Drill a 1/4-inch hole on either end of the crack using a drill and a wood-boring bit if you’re repairing it. Spray high-density foam insulation through the perforations if the tub requires strengthening behind it. When the foam begins to overflow from the hole, stop spraying and wait for it to harden before cutting off the excess with a utility knife. Make a small indentation in the foam to accommodate the repair compound.
Step #4. Combine Epoxy and Hardener
Read and adhere to the mixing instructions for the epoxy you are using. Apply enough epoxy to a piece of disposable cardboard to create the repair, then add the appropriate amount of hardener and mix to a uniform consistency with the kit’s applicator or a plastic putty knife.
Step #5. Use the Filler to Repair Large Hole in Fiberglass Tub
Apply the filler evenly within the taped-off area, ensuring sure it fills the hole and overfills the area so you can sand it down. The patch should be roughly 1/16 inch above the tub’s surface. If you’re using a fibreglass patch, apply it to the wet epoxy according to the manufacturer’s instructions. Remove the tape as soon as you’re finished filling and levelling, which will be impossible if you let the filler set first. Allow the epoxy to cure completely as specified.
Step #6. Repaint the Area and Begin Sanding
Use a double row of fresh painters’ tape to protect the tub’s surface from sanding, and then use 400-grit wet/dry sandpaper to sand the patch as flat as possible. When you’re finished, sand the area as smoothly as possible with 600-grit wet/dry sandpaper. Finally, remove the tape, wet the 600-grit sandpaper, and sand the repair edges to blend them as smoothly as possible into the surrounding tub surface.
This is the step that separates a professional refinishing job from a mediocre one, so take your time. It’s a good idea to shine a working light on the surface to see and sand minor ridges and scratches.
Step #7. Finish with a Spray Finish (Optional)
If the colour of the repair compound differs significantly from that of the tub, you might consider covering the repair with weatherproof spray enamel. This won’t make much of a difference unless the enamel is the same colour as the tub or you spray the entire tub. If you choose this route, make sure to tape off the drain, overflow plate, and any other portions of the tub that you don’t want to paint, and make sure to wipe out the fix with alcohol or acetone before spraying.
Step #8. Apply Polishing Compound to Repair Large Hole in Fiberglass Tub
If you do not want to paint the repair, apply a polishing compound to it and buff it with a soft cloth until the sheen resembles the rest of the tub. After the paint has dried, add car polish to the entire tub as well as buff it with an electric buffer.