Keeping a shed as weathertight as possible is a smart way to protect the investment you've made in this outdoor building. One way of helping keep your shed well-sealed is to add corner trim on the exterior corners. Corner trim prevents water from working through the joints and, in addition, your shed will have a more polished appearance. Adding corner trim takes only simple tools.
Measure the length of the first corner you'll be installing trim onto, from the top of the wall to the bottom. Cut a length of trim to match the length of the corner with a saw.
Place the trim onto the corner and nail it on with 6d galvanised finishing nails, spaced every six inches along the length of the trim.
Move to the next corner you'll be installing trim onto and repeat the process until all the corners have trim.
Apply a bead of silicone caulk along the edges of the trim pieces where they meet the shed wall. Let the caulk dry for the amount of time recommended by the manufacturer.
Paint or stain the trim pieces to match your shed's exterior colour.