DIY Home Improvement Tips: How to Repair a Crack in a Fiberglass Tub or Shower Stall

Although fiberglass is a tough material, it is not uncommon to accidentally crack your bathtub or shower stall. Before replacing the entire unit, consider repairing the crack. A meticulous homeowner with some basic home improvement skills can fix a small fiberglass crack.

Before attempting to repair the damage, determine the cause of the crack. If a fall or other object caused the crack, you can easily fix it. If the crack’s cause is unknown, it is possible that the structure underneath the tub cannot support the weight being placed upon it.

If this is the case, you must add more support to the tub before proceeding. Otherwise the same area will crack, or the crack will become more pronounced soon after you fix it.

If the crack is in the sides of the bathtub, drill a hole and fill the cavity with an expanding foam sealant. This will provide extra support for the area and prevent an additional crack. You must allow the sealant to cure at least 48 hours before continuing to fix the crack.

If the crack is on the bottom of the bathtub, it is probable that the tub was installed without a mortar base. Form sealant will not work in this case, it will not be strong enough to withstand any weight and prevent another crack. Instead, the tub must be removed and a mortar base poured before proceeding to repair the crack.

Keep in mind that a fiberglass tub repair will not restore your tub to new condition. If this concerns you, it may be easiest to replace the bathtub rather than attempting to repair the crack in the old one. Fiberglass bathtubs are available at several price points, making it an affordable option.

If you must remove your tub for the repair, strongly consider replacing the bathtub rather than fixing the fiberglass. There may be a larger initial cost, but your new tub will undoubtedly look better and be more reliable than an older model.

If you want to make a repair, you will need a fiberglass repair kit, dremel, and epoxy paint to match your tub. All of these items should be available at your local home improvement store. You can also look at any auto body repair store for the fiberglass repair kit.

Make sure that the tub or shower stall is completely dry before attempting a repair. Once the tub is dry, sand out all of the broken fiberglass with a dremel or similar tool. It is important to continue to sand until you reach sound and well bounded fiberglass.

Then cut the dry fiberglass patches to match the hole in your tub. Fiberglass consists of many thin layers bounded together, you much replicate this when making the repair. Cut all of the pieces while dry, making sure they fit exactly into the hole. The last piece should be flush with the surface of your tub.

Then you can mix the epoxy and resin according to the manufacturer’s instructions. Dip each piece into the mixture and apply carefully into the hole. Make sure each piece is smooth and adheres to the piece beneath it. Most holes should only take 3-4 layers.

Then you must wait for the fiberglass to harden. Fiberglass is not waterproof, so you must apply a waterproof sealant (usually contained within the kit) for the patch to hold water.

After the patch is made, wait at least 48 hours for the fiberglass to cure. Then test the seal by filling the bathtub with water, and applying a piece of painter’s tape at water level. Wait at least four hours to evaluate the strength of the repair. If the water level has not fallen you can now repaint the bathtub to conceal the repair.

To begin the painting make sure the bathtub is completely dry including the area around the crack. Wearing gloves and an eye mask use muratic acid and steel wool to thoroughly clean the tub before painting. Be sure that the area you are working in is well ventilated and follow the manufacturer’s instruction when working with the muratic acid.

After the tub has been carefully cleaned, you can then recoat the entire area with epoxy paint for fiberglass tubs and showers. The epoxy paint will restore the sheen to your tub and further mask the repair. Allow the entire area to dry according as specified by the epoxy paint instructions.

In order for this repair to look professional, you must be patient and meticulous during the process. Any rough edges around the crack or paint streaks must be dealt with immediately, or you risk creating a very ugly patch job. If you are not interested in fixing it yourself, call a professional. A repair should cost $400-$600 depending on where you live.

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