Credit: Photo: Azek

For signature work, think in circles. Adding a curve to a deck frame, and bending the decking and guardrail to match, is a sweet detail and an upsell. Or you can braid an S-curved deck board through the decking. The key component is cellular PVC, a growing decking category thanks to its durability, scratch- and split-resistance, and the fact that it bends well when heated. Here are some tips.

ROUND-FRONT DECKS For shallow bends — nothing severe — you can cantilever the joists. A good rule of thumb is to limit the cantilever to less than one-eighth the span of the joist — I don't like to go more than 24 inches past the beam. You can beef up the joists to go a bit further, but make sure that the structure can support the overhang.

For deck sections of less than 12 feet wide, use the decking material to lay out the curve. Once you've determined where you want the bend to start and finish on the left and right band joists, mark it off by setting two nails. Pulling the on-edge deck board between them allows it to bend in a uniform circle segment. At the peak of the circle, drive a nail to pin the board in place.

Scribe the joists along the curve, cut off the ends, and install vertical blocking as backing for the front band wrap. Behind the vertical blocking, install blocks on the flat to support the heated decking while it cools after installation.

For bigger curves, take some tar or rosin paper out to a wide flat surface, swing an arc with a string, mark it on the paper, and transfer marks to the deck.

BEND THE DECKING Heated PVC and composites set in about five minutes. Use toe-screws in the edges to snug the bent material against a series of stops; on-edge decking skirts will follow the curve of the framing. To create S-curves, bend the decking between rounded 2-by blocks screwed to the joists. —Mark Clement is a freelance writer and former contractor in Ambler, Pa.