Methods of finishing wood sidings at exterior corners will be influenced by the overall design of the house structure. Lapped corner boards are appropriate for some designs and mitered joints for others, and in modern construction, metal corner caps are almost always used for outside corners. Interior corners may be formed with square lengths of solid wood, two thicknesses can be used to secure required size if needed.
Corner boards are used with bevel or drop siding, generally of 1 or 1 ¼ inch material, depending on thickness of the siding. It can be either plain or molded, depending on the architectural treatment of the house. The corner boards may be applied vertically against the sheathing, with the siding fitted tightly against the narrow edge of the corner boards.
Joints between the siding and the corner boards and trim should be caulked or treated with a water repellent. Corner boards and trim around windows and doors are sometimes applied over the siding, a method that minimizes the entrance of water into the ends of the siding.
Mitered corners must fir tightly and smoothly for the full depth of the miter. To maintain a tight fit at the miter it is important that the siding be properly seasoned before delivery and be stored at the site so as to be protected from rain and moisture.
The ends should be treated with water resistant coating, and the exposed faces should be primed immediately. At exterior corners, the siding is butted against a corner strip of 1 or 1 ¼ inch material, depending on siding thickness.
Metal siding corners are made of light gauge aluminum or galvanized iron, and used with bevel siding as a substitute for mitered corners. They are available at most
Lumberyards and building supply stores. Installing metal corners is easier than getting a good fit on mitered corners or fitting corner boards.