Step 1 Measure Railing Run
Measure the exact dimension of each railing run. A railing run is a straight section of railing uninterrupted by stairs or other changes in direction. Calculate the number and location of posts and the gap between balusters for each run. Plumb and attach each post with two carriage bolts or lag screws. Stagger the fasteners on both sides of the centre of the post to prevent splitting. Cut notches in post before attaching, if necessary for the railing style. Make notches for rails the same depth as the notches on the rim joist. Fasten each rail to the posts. Drill pilot holes for fasteners at the ends of each rail to prevent splitting.