DIY Deck With Corner Stairs

Designate on your plans for a rectangular deck a 45-degree angle at one corner. Make the angle cutout 33 1/2 inches -- 32 inches plus two half-widths of the 2-by-12-inch stock, or 1½ inches -- to permit the attachment of three stair stringers on 16-inch centers. Flank the corner angle with four additional stair stringers on each side, with the flanking stairs each 49 inches long. Sketch two more stringers to extend from the corners of the 45-degree cutout.

Place four circles on the plan to indicate precast concrete pier blocks under the two stringers extending from the corners of the angled cutout and under the two stringers farthest from the corner. Estimate the distance of the pier from the deck’s edge, called the rim joist, by consulting the dimensions of precut two-, three- or four-step stringers of pressure-treated wood, available at home centers. Select the number of steps based on the desired height off the ground of the stringers and piers.

Frame the main platform of the deck following normal deck-building techniques, locating pier blocks, support posts, beams and joists according to your plans. Snap a chalk line on one corner to indicate the 45-degree cutout. Draw over the chalk line with a carpenter’s pencil and extend the marks down the sides of the joists with a speed square. Cut off the joists along the marks with a reciprocating or circular saw.

Cut a rim joist with beveled edges to cover the cutoff joist ends, and clamp it in place. Toenail the cut joists to the back of the rim joist. Bevel the bottoms of 2-by-6-inch boards to match the angle of the stringer’s bottom edge, and attach the 2-by-6-inch boards under the rim joist to support the backs of the stringers. Nail strap ties down the back of the rim joist and 2-by-6-inch boards. Leave an extra 5 inches at the bottom of the strap tie hanging, so it later can be nailed to the bottom of the 2-by-6 and the stringer after the stringer is in place.

Lay the concrete piers in place according to your plans. Center one stringer on top of each pier, laying its other end against the rim joist. Press a slopeable joist hanger against the rim joist and around the bottom of the stringer. Nail the joist hanger into the rim joist and the stringer with galvanized nails. Nail the loose section of the strap tie in the previous step to the bottom of the 2-by-6-inch board and the stringer.

Measure and cut beveled ends for doubled fascia boards to sit vertically, and connect the bottom riser of the four stringers that rest on piers. Toenail the doubled fascia to the stringer.

Attach three stringers between the 45-degree corner and the doubled fascia by hammering joist hangers into slopeable joist hangers at each end. This creates support for the stair treads between the two central piers. Similarly attach three stringers between the rim joist and fascia to create support for stair treads on each side, between the central piers and the end piers. Nail scraps of joist lumber as blocking between the stringers leading to the central piers and the adjacent stringers, just behind the fascia.

Measure and mark deck boards to create step treads -- two per stringer step cutout. Mark an angle as needed for deck boards where they touch one of the angled stringers that meets a central pier. Cut the angle so it falls to the midpoint of the angled stringer. Attach each deck board with two deck screws wherever it meets a stringer step cutout.