Drill carefully, then install bolts
Fastening towel bars, shelves or hooks to a fiberglass or plastic shower surround can be tricky. The surround is simply too thin to hold screws and there's often a gap of 1 in. or more between the surround and the wall studs behind it. But with 1/8-in. toggle bolts, you can mount most light-duty hardware (like the adjustable showerhead bar shown here). Keep in mind that this leaves big holes (3/8 in.) in the surround that can't be patched later, so anything you mount will have to stay there permanently. The mounting system shown here isn't strong enough to support the full weight of a person, so we don't recommend it for installing safety grab bars.
Photos 1 – 3 show how to use 1/8-in. toggle
bolts in a surround. Everything you need is
available at home centers and hardware stores.
Here are some pointers:
- Some areas of a fiberglass surround may be reinforced with plywood. After you mark the hole locations (Photo 1), drill 3/16-in. holes. If you strike plywood behind the fiberglass, you can drive in stainless steel screws instead of using toggle bolts. If you don't hit plywood, drill 3/8-in. holes.
- When you're drilling through the side of the surround where the shower valve is mounted, apply only light pressure as you drill. Otherwise, you might suddenly punch through the surround and puncture pipes.
- When you buy toggle bolts, also buy brass machine screws to replace the steel screws that come with the toggles. Steel heads will rust and stain the surround.
- When you tighten the toggle bolts (Photo 3), it's OK to use a drill. But do the final tightening by hand. Too much torque can crack the surround.