Curved Deck Stairs

Curved Deck StairsFigure 17. Once the frameis removed and the stringerssupported, finishinstalling the last treadsand risers.Figure 18.Intermediateguardrail postscan simply beextensions ofsupport posts.Figure 19. Use fascia material for the finished skirtboards, and decking for the treads.Curved stair stringers need intermediate supports, whichI extend upward to double as guardrail posts. I space postsalong the arcs at equal intervals — between 4 feet and 6 feetapart — and set them on footings (Figure 18).It usually takes as long to apply the finishes as it does tobuild the curved stair frame — and may take longer, dependingon the details. Skirt boards can be mitered into the risersor closed. Closed skirt boards require less work and look betterover time. Clamp, glue, and screw synthetic or rot-resistant-woodskirts alongside the stringers, shimming whereneeded to maintain a fair curve (Figure 19).Water that gets beneath the treads needs a way to drain,so bore a few 3 ⁄4-inch holes through the structural treads.Lay 1 ⁄2-inch or thicker wood strips over the rough treads asspacers for the finish tread decking. I rip the finish deckingstrips on a taper and ease the edges. This looks much betterthan having a couple of straight decking strips and a wedgeshapedclosing piece meeting the riser at the back of thetread. This approach won’t work with capped decking, however,because easing the edges of the tapered pieces wouldexpose the capped decking’s substrate. Space the finish riserboards 1 ⁄4 inch from the structural risers for drainage.Bending and laminating curved rails is an article in itself.Done correctly, a curved rail needs the same helical shape asthe stringers. One workaround is to cut rails out of wide 2-bystock to match the curve of the stair, but this only works ifthe intermediate posts are less than 4 feet apart. Rails donethis way will have a slightly odd slope as the rail turns. ❖Mike Guertin is a builder in East Greenwich, R.I., and a regular presenterat DeckExpo.8 Professional Deck Builder • July/August 2012