Installing door trim—professional results in minutes

Installing trim around a door or window opening is a relatively simple process. Essentially, you will place the trim in its intended spot, mark where you will make a cut, then install it. 

Installation is typically done with nails, but you can also attach the trim with glue. If you use adhesive, you may still want to put in a couple of nails to keep the piece in place while the glue dries. With clamps or a fast-setting glue, it may be possible to use no nails at all.

Here is a list of the tools and supplies you will need:

• wood or PVC door and window casing
• pencil
• caulk gun and construction adhesive
• tape measure
• mitre saw
• hammer and trim nails (if you choose to use nails)
  
• safety gear: gloves, protective glasses

First, make sure there are no obstructions in the way of the trim, such as nails or staples. Then proceed as follows:

1. Take a piece of trim and place it on the hinge side of the door. 
2. Position it so that about 3mm of the jamb is showing. The reveal must be even from top to bottom so that the trim will be straight. Note: do not put the trim too close to the hinges, or you may impede the operation of the door. 
3. Next, mark the trim about 3mm past the corner where the door jamb meets the header. This mark is where you will cut the trim at a 45° angle.
4. After cutting the piece, glue it or nail it into place. Use an all-purpose construction adhesive, putting a bead of glue about 1cm from the edges of the trim. If any seeps out during installation, wipe it away immediately with a soft cloth.
5. Continue with the next piece, the header trim.
6. Cut a 45° angle the opposite way to fit the piece already installed.
7. Put the trim in place on the header, again keeping an even 3mm reveal on the header jamb.
8. Mark for your next cut, about 3mm past the edge of the jamb on the other side of the doorway. 
9. After making this cut, install the header piece of trim as you did with the first piece.
10. The final piece is easy. Simply stand the final side up in place and mark it where it meets the bottom edge of the header trim piece. Then cut and install.

Installing window trim is much the same as above. The difference is where the side pieces of trim begin. Rather than starting at the floor they will start at the window sill. The rest of the process will be the same as if the window was a very short door.

The exception would be if the window does not have a sill. In such a case, you will install trim all the way around the window, metring all four corners. This is sometimes called “picture framing” a window. 

If any corners or ends of a trim piece were to come loose at some point, we have a quick fix. Try Loctite Stik’N Seal Indoor Adhesive. It’s an all-purpose adhesive that bonds to virtually everything. This adhesive won’t run due to its thick consistency and sets in about 10 minutes. It dries transparent and is nearly invisible in many applications.