By Mike MorrisMore in Home Improvement
Before installing crown molding, test fit a piece of molding in place (Image 1), and mark the height of the molding where it meets the wall below the ceiling. Use a level, or laser level, to extend this mark along the walls from corner to corner (Image 2). Use an electronic stud finder to mark all wall studs and ceiling joists (Image 3) along this line. These marks will be your nailing points when the moldings are installed. Some carpenters prefer to install wood blocking against the wall and ceiling joint to serve as a secure nail base for the molding (Image 4). Use wood blocking if your molding is wider than 4-3/4 inches.
Where horizontal or “running” lengths of molding meet, join them together with overlapping (lap joints) 45-degree-angle cuts (Image 5). This will prevent visible gaps from opening at the joint as the molding dries and shrinks. Apply construction to the inside of the 45-degree cuts to get a tight seal then secure the pieces together with finish nails. For corner seams, apply caulk to the coped end (Image 6) then secure with nails. Wipe away any excess caulk that may ooze out of the seam.
Wall corners are rarely perfectly square. To avoid problems and wasted material, first cut and join short random-length molding pieces and pre-construct sections to fit all outside and inside corners. It is easier to work with short pieces and make trial-and-error cuts if necessary to get a tight fit in each corner than to attempt to make longer lengths meet precisely. After cutting the corner pieces, glue and nail them together, then cut 45-degree overlapping angles on the outer ends where they will be joined to intersecting running lengths. If you opt to build all of the corners at one time and install them afterward, mark each corner according to its location.
If you use a hammer and finishing nails to install hardwood molding, use a drill to pre-bore nail holes to prevent the wood from splitting. A pneumatic finishing nailer is the preferred tool for installing moldings. It makes working overhead much easier, prevents hammer marks, and eliminates pre-boring because power-driven nails will not split the wood.
Use wood putty or paintable caulk to fill slight gaps where moldings intersect. Use spackle to fill in the nail holes if you are painting your molding. If you have any nails protruding from the molding, use a hammer and nail set to the recess them. Caulk along the top and bottom edges to seal the moldings against the wall and ceiling.