A fiberglass shower pan does not need grout unless it will be tiled. Tiling over a fiberglass pan is not recommended, but if you have already done so, you have to grout it too to seal the spaces in between the tiles. Here’s how.
Step 1 - Determine Whether the Pan Can Be Grouted
Use a non-flexible pan. Flexible pans cannot be tiled and grouted because the tiles will crack after a short period of time. Do some research to learn which brands of fiberglass pans can withstand tiling. User reviews are a great resource.
Step 2 - Preparations
Choose a tile design that matches the walls of the shower. Do not set large tiles for the floor. Choose smaller tiles, as they are easy to slope. When pouring the tile mortar over the pan, slope it towards the drain to avoid flooding.
Step 3 - Tiling
If you haven't tiled the pan, now is the time. Start tiling from the middle of the floor towards the walls. Apply thinset mortar evenly to ensure that the tiles are level with the slope. Check for bulges and unevenness in the installation. Once the tiles are in place, allow the mortar to dry.
Step 4 - Prepare for Grouting
Because the spaces between the tiles are smaller than other tile installations, it is best to use non-sanded grout. Look for grout products that are designed specifically to withstand the moisture in the shower. Allow the mortar to dry thoroughly until it hardens fully and sets the tiles in place. Remove any excess mortar between the tiles.
Mix the grout in a bucket and slowly add water. Stir the mix with a trowel. Never pour the contents of the grout into the bucket. Add more water to make the mixture wet. If mixture is too wet, add more grout until it reaches the proper consistency.
Step 5 - Grouting
Use the rubber float to squeeze the grout between the tiles at a 45-degree angle. Do not worry if the tile surfaces become hazy with each application of grout. That can be dealt with later using a damp sponge.
When the joints are grouted, allow them to cure according to the manufacturer’s instructions. Wipe the extra grout from the tile with a damp sponge. If there are any incorrectly grouted areas, re-grout them. Clean the excess grout and let it cure completely for up to 72 hours.
Step 6 - Sealing the Grout
Seal the grout with a waterproof sealant to ensure maximum moisture protection. Allow the sealer to dry completely before using the shower.