How to Build Deck Steps With Round Corners

Sketch your ideas on graph paper -- showing the position of the deck relative to the back or side of your house. A common option is to create a sinuous curve coming off a rectangular frame on the top platform of your deck, leading to two lower, and similarly curved, wide steps that connect you to ground level. Consult with an architect or engineer to ensure your joists and beams can handle the spans needed, revising your plans as necessary, and get a permit for your deck with curved steps from your municipal planning department.

Pour concrete footings and install posts, a ledger, beams and joists for the main rectangular part of the deck per your deck plans. Add joists to support the curve of the rounded step by bumping out additional joists to additional posts -- for example, adding a small rectangle and an adjacent small triangle to one side of your main rectangle to support a teardrop shape.

Install deck boards by fastening them with two galvanized deck screws to each joist, allowing the ends to run long over the edge of the joists in the teardrop or similarly curved area. Hammer a nail on the deck surface where indicated in your deck plans to establish a point for the prescribed curve radius. Tie a string around the nail and around a carpenter’s pencil at the length indicated for the radius. Scribe the deck boards by swinging the pencil on the string along its arc. Cut the deck boards with a circular saw if the curve is shallow and gradual, or with a jigsaw if the curve is tight.

Construct your lower rounded steps by installing additional footings and posts according to your plans, with a 2-by-8 rim joist running from post to post just above the ground. Run regular joists on joist hangers from the rim joist to a 2-by-8 support joist running from post to post of the main platform. If your plans call for an intermediate rounded step as well, create yet another rim joist that rests on the regular joists of the bottom step. Hold the intermediate rim joist in place by toenailing 2-by-8 blocking between the intermediate step’s rim joist and the rim joist of the main platform.

Lay additional deck boards across the lowest and intermediate step, letting the free ends run long over the curved area in step 3. Scribe the edges to a similar radius to that of the top platform, or a different one for added visual interest. Cut the deck boards at the scribed marks.