Can I recaulk joints in a fiberglass shower surround after removing old caulk?

Question

There's a fiberglass shower stall in my bathroom. It consists of two wall panels and one pan, and there seems to be glue/caulk in the seams between them, as shown in the photos.

I wonder if I can recaulk them with silicone. If yes, shall I remove the old glue/caulk before caulking? This is not easy since the glue/caulk is inside the seams. Moreover, is there any requirement on the type of silicone I shall apply?

I don't have the installation instructions or make/model of this shower stall kit, thus cannot find any useful information.

Answer 1

• Most such showers are designed to remain uncaulked for drainage.
• I sometimes caulk such joints for aesthetic reasons, but only after considering whether it'll cause problems.
• Always remove old caulk before recaulking, if possible. Your bead should be minimal and coved to appear as a smooth channel in the surround. Adding caulk to caulk is almost guaranteed to look like poop.
• Silicone won't bond to silicone. You can typically caulk over latex, but see above.

I only use pure silicone caulk for such situations. It stays cleaner than acrylic and bonds better. It also retains some surface sheen, which better matches the acrylic surround.

My strategy for such joints is to clean thoroughly, then fill the gap just enough that I can tool out a nice smooth surface with a finger. That joint should look like it was molded in place when you're done.

Answer 2

I would not use a 100% silicone caulk for this. Unless you blue tape either side of the caulk line and then wet peel the tape (before the silicone has set up) you will have a big mess.

Most of the acrylic latex caulking sold today is "siliconized" (contains some silicone). You can caulk and finger wipe your joint and then use a wet rag to clean up the fiberglass area around your caulking. It is flexible, it is easily workable, and easily repairable. It seems to me that most silicone jobs attract mold and/or mildew (especially in a shower) and just look bad after awhile.