How to Build Deck Stairs with Pre-Cut Stringers

Position the top of each stair stringer flush against the deck ledger board. Ensure the stringers are plumb and parallel to each other. Secure the stringers to the ledger board using lag screws or structural screws specifically designed for exterior wood construction. Drive the screws through the stringer and into the ledger board, ensuring at least two screws per stringer. For added support, if the stringer extends past the rim joist, secure the bottom of the stringer to the deck frame joist using appropriate fasteners, such as joist hangers or structural screws, following manufacturer recommendations for load-bearing connections.

If your stairs are tall or will experience significant traffic, it is recommended to provide a solid base. Dig a hole and pour a concrete footing, or attach a treated lumber support block to the ground or a stable existing structure. Ensure the top of the support is level and at the correct height to receive the bottom of the stringers. If using a concrete footing, use a post anchor to connect the stringer to the concrete. If using a lumber block, secure the stringer to the block with appropriate fasteners.

Place the first tread onto the bottom steps of the stringers. Ensure the tread is level and its front edge overhangs the riser slightly (typically 1 inch). Secure the tread by driving screws through the tread and into the stringer notches. Use at least two screws per stringer. Repeat this process for each subsequent tread, working your way up the stairs. Ensure each tread is level and consistently spaced from the one below.

If you are adding risers, cut pieces of lumber to fit snugly between the front of one tread and the back of the tread above. Align the top of the riser with the underside of the tread. Secure the riser by driving screws through the riser into the back of the tread above and into the stringer. Repeat for all steps.

Securely attach the bottom of the stair stringers to the deck frame using appropriate fasteners, such as structural screws or bolts. The top of the stringers should already be secured to the deck ledger. If handrails are required by local code, install handrail posts at the top and bottom of the stairs, and potentially at intermediate points for longer runs. Posts should be securely bolted to the deck frame or substructure. Attach balusters to the treads or stringers, spaced according to local building codes (typically no more than 4 inches apart). Finally, attach the handrail to the posts, ensuring it is at the correct height (usually 34-38 inches from the tread surface).

Walk the stairs and test for any wobble or instability. Check that all screws and fasteners are tight and properly seated. Ensure treads are level and secure, and that the handrail is sturdy. Sand down any rough edges or splinters on the wood. Apply a sealant, stain, or paint to protect the wood from the elements and enhance its appearance, following the manufacturer's instructions for application and drying times.