I recently put some FRP in a bathroom to shore up the area around the shower head. If you’re wondering how to cut FRP panels, or you’re just looking for the best way to cut FRP, I have some tips.
FRP isn’t necessarily the most attractive material, but if you need a waterproof material to protect a wall from moisture, it’s probably your cheapest bet. Besides using it inside a shower, I’ve also used it to waterproof a bathroom window that was near a shower to prevent future moisture damage.
Mark your line
You can mark easily on either side of an FRP panel, but I prefer to mark on the back where the surface is smooth. I get a straighter line with less effort. Use a carpenter’s square and a straightedge to get a perfect line. Your cut will only be as good as your line.
Scribe and snap
In a pinch, you can just slice into the panel with a good sharp knife and then fold back and forth along the slice. Don’t try to cut the FRP all the way through. FRP looks like it should be really easy to cut, but the fiberglass component makes it much harder. Just get a good groove in the material. After a few back and forth motions, it will break relatively cleanly and without making a mess. The fiberglass content keeps it from breaking completely smoothly like you can get with sheet styrene using this method.
You can dress the edge with a few swipes of 60-grit sandpaper to smooth it out. If you don’t have many tools and don’t want to spend money on tools, this method gets it done.
But, admittedly, I cheated here. If you actually want to cut FRP, here’s how to cut FRP panels quickly. This method is faster.
The best way to cut FRP panels (or at least my favorite)
I bought a cheap electric metal shear for about $50, and I think that’s the best way to cut FRP. It’s rated for 14 gauge metal. I don’t know how it does on metal, but it cuts FRP very quickly and easily. If I were going to cut metal, I think I would rather have a more expensive one. But a cheap shear works well on soft plastic. The effort involved is comparable to cutting paper with scissors.
The only downside with this method is you’ll waste about 1/4 inch of material. If you’ve ever used a nibbler tool, it works along the same lines, only it’s electric and it cuts strips instead of just bits. So after you mark your line, be sure to mark your waste side. Then line the shear up so two of the shears are on the waste side, pull the trigger, and guide it along the line. You can cut a section of panel in minutes with this tool, with minimal mess. Even with my shaky hands I got relatively straight cuts. To me, the ease and convenience outweighed the small amount of wasted material.
If you’re not completely happy with the edge, you can sand it straighter after you finish cutting. Use about 60 grit and wear a mask to avoid breathing in fiberglass particles.