How to Build 4x4 Spindle Deck Railing

Measure the deck with a tape measure to determine the length of each railing, from post to post. Check local building codes for spacing of spindles, the vertical elements between top and bottom rails; most require no more than 4 inches between spindles. Use this math: a 4-by-4-inch post is actually 3 1/2 inches square; turned portions are no more than 2 inches, so spacing spindles with centers 6 inches apart will yield 4-inch code spacing.

Calculate the number of spindles required for each portion of the railing; divide the length in inches by 6. Set 4-by-4-inch square posts at the corners and openings, such as stairs, around the deck if they are not already installed. Secure them to the deck floor with metal post brackets screwed with galvanized screws and a screw gun into the deck and the post.

Notch the posts using a circular saw with the blade depth set to cut 1-inch slots into the post for top and bottom rails, typically 2-by-4-inch boards; adjust the notches if using preformed rails with rounded edges. Make the bottom notch with its bottom 3 1/2 inches above the deck floor, and the top notch so the top rail will be 36 inches above the floor.

Buy 4-by-4-inch decorative spindles, with a square top and bottom and rounded edges between, typically varied between long tapers and short round sections. Divide the length of each railing by 6 to determine the number needed, with the required 4-inch spacing. Get top and bottom rails in lumber to match.

Assemble the railings on the deck floor or other flat surface one section at a time. Cut 3 1/2-inch notches in the bottom of the top rail at the marked spindle locations, with a circular saw or table saw. Cut 1-inch-deep slots on each side of the center point for a spindle and chip out the wood between slots. Fasten the spindles to the top rail with galvanized screws driven with a screw gun diagonally through the top of the spindle into the top rail. Place these on the back side of the rail.

Notch the bottom rail and set it in place under the spindles attached to the top rail. Fasten the bottom rail to the spindles with two galvanized screws through the bottom rail into the bottom of each spindle. Set the assembled railing between posts and slide it in place in the notches on the post. Work slowly and have help so one worker slides the railing from each end. Fasten the rail ends to the posts with diagonal galvanized screws.