How to Bend PVC Trim

Q. I have heard that 5/4 PVC trim can be bent with “heat blankets,” but I do not know the best kind to use. Are there other heat sources that would work, and how do you form the curve once the material is heated?

A. Nathan Nebbia, owner of Built Better by Nate, based in Berwick, Maine, responds to this question in the Journal of Light Construction: 

I do all of my PVC bending with Heatcon heat blankets. I use the deck forming kit, which works for PVC trim stock and includes blankets wide enough (8 inches) and with enough heat output to also bend solid PVC decking. (Note: They do not work for composite or cap-stock materials.) The blankets are 10 feet long. A kit comes with two blankets, which will work for one 10-foot length, or four blankets that can do up to 20-foot lengths. They are not cheap (currently $2,700 for the 10-foot kit), but I think they are worth the investment.

For the best and quickest results, you should use two blankets—one under the stock and one on top of it. To make an “oven” that fits the blankets and the stock, I build a box with a hinged lid out of solid 2-by stock and screw cement backerboard to the inside surfaces. I have also used two insulation batts, sandwiching the blankets and trim between them, but that method takes longer, as it doesn’t hold the heat as well as the box does.

The cheap way to do it—without blankets—is to make a box, put a propane torpedo heater at one end, and blow heat through. This, too, can be made to work, but the heat doesn’t disperse as evenly as you want it to for bending an entire length of trim. Also, it’s almost guaranteed that you will overheat the end of the trim near the heater, which will make it floppy and can distort the material, while the far end will be stiff. As a result, the trim will be very difficult to handle.

To read the rest of Nebbia's response, click here for the full JLC article.