Multi-Feature Curved Deck: Building the Stairs
Stairs on the curve are a challenge, so take your time to plan them out.
The curved stairs on this deck are about as challenging to frame as stairs can get, but the finished product looks great and provides handy overflow seating. In planning your stairs, bear in mind that adults are most comfortable with stairs whose tread (the part you step on) and riser (the height of each step up) come within a couple of inches of totaling 18 in. In addition, stairs should be at least 4 ft. wide—a comfortable distance for two people using the stairs to pass side by side.
The stairs leading up to the first level of this deck need to climb an overall distance of 38 in. from the pavers to the decking. That calls for five steps overall, each with just over a 7-1/2-in. rise—an ideal step up. The curvature of the stairway complicates framing, though once the bracing for the stringers is added, it is much like standard stair framing.
1. Add bracing. A typical stringer just misses the rim joist when set in place. Add a short piece of 2×6 as bracing to support the backer board.
 2. Cut a trial stringer. Lay out and cut a trial stringer. Set it in place and check that the rise is consistent from the pad at grade to the deck. Notice that a strip of 1/2-in. PVC is added to the foot of the stringer as rot defense. |
 3. Lay out the pad. Once you are satisfied with your stringer layout, cut a couple more. Set them in place as shown. Adding a strip of 1/2-in. PVC helps establish the radius along which you can set paver blocks or a concrete pad. |
4. Install the stringers. With the pad in place, you can install the stringers by toenailing structural screws. The decking manufacturer specs a maximum 10-in. span for steps. The stringers are set 12 in. apart at the pad but will have blocking to support the bottom tread.
5. Add the top and bottom risers. To even out the curve to stabilize the stringers, install the top and bottom risers using pluggable deck screws. Do a test bend of the tread. Back out the screws slightly to fill any small gaps between the tread and the riser. Heat-bend the treads just as the decking was bent.
6. Install any lights. Add midway risers and begin installing the treads. Install any riser lights before installing the final treads.
7. Complete the tread installation. Continuing to adjust risers by backing out screws where needed, complete the installation of the treads. Muscle in the tread where the bend is not perfect.
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