Trimming an existing interior door

How to trim an existing door.

When renovating a house one of the easiest ways to give the house a face lift is to change the trim. In today’s world there are endless options of style, size and material to pick from. Here is how to re-trim an existing door properly;

• First things first remove the old trim. Try to remove the trim so that you do not damage or dent the door jamb, use a flat bar for this and you should have little to no problems.

• Clean the existing jamb. Remove any nails, staples, caulking, and excess paint or wood splinters from the end of the jambs. This will make it simpler to install the door trim.

• Check to see that the new trim you are adding to the door will not be impeded by the drywall. Sometimes the existing drywall can have humps and bumps in it that can push your trim out and make it quite difficult to install flat and straight. Cut any drywall back that is in the way but make sure that you don’t cut beyond where the trim will cover or you will be forced to do a drywall repair afterward.

• Check that the door stills shuts properly now that the trim has been removed. Sometimes people do not realize that they are suppose to hang the door with shims before they trim the door, so instead they install the door so that the trim holds the jamb in place.

• If the door needs to be adjusted, take the time and properly shim and nail the door so that it opens and shuts properly. You need to make sure that the door looks square and with a level check that the existing jambs are installed level. This will make it easier for you to install your trim.

To trim the door properly you will need the following tools;

• Sliding compound saw or “chop saw”.
• 16 or 18 gauge trim gun or both with an air compressor.
• Glue.
• Wood filler.
• Tape measure and a pencil.
• Hammer and a nail set.

You can get away with not using a lot of power tools but if you have more than one door to trim then I recommend that you either buy or rent the equipment, it makes a more professional job.

You always start with the piece of trim on the top of the door frame. This piece of trim will be probably be the shortest piece of trim on the door and it will be angle cut on both ends.

Measure the top piece of trim by measuring from the corner of your door frame to the corner of your door frame. Then add 1/8 of inch for each side so that you will have a reveal at the edge of the door frame. So if the measurement of the jamb widths is 36 inches then your measurement for the piece of trim will be 36 ¼”.
As long as the door you are trimming is close to square and level you should be able to make the two angle cuts on the top piece of trim at 45 degrees.

Cut one side of your trim with the 45 degree angle and then measure from the short point your 36 ¼” and make a mark. Then cut the opposite 45 degree angle starting at your mark cutting away from it. As long as you measured and cut properly this should fit on the top.

Line the piece of trim up so that you have an 1/8” reveal on each end to match your measurement and then line the piece of trim up so that there is an 1/8” reveal on the top of the jamb. Use the trim gun to nail the piece of trim in place, be very careful when nailing the trim to the jamb that you do not split the jamb.

Measure the side trim from the inside point of where your top piece of trim starts to the ground. Deduct 1/8” so that the trim will not rub on the floor.  When you cut the side trim cut the bottom end square first and then measure up the trim and mark it where you want to angle cut it. Cut your 45 degree angle. If the door is level and square the two pieces of trim should come together perfectly.

But since you are trimming an existing door you will probably have to adjust your cut so that the joints fit tighter together. When you have successfully obtained a tight fit on the joint between the two pieces of trim, nail it with the trim gun. Leave a 1/8” reveal on the jamb just like you did on the top piece of trim. Put a nail at the top corner of the trim so that the nail is driven sideways through both pieces of trim holding them together.

If you are worried about the trim pulling apart because of expansion and contraction adding wood glue to the joint between the two pieces of trim will help.

Do the other side of the jamb the same way that you have just completed the first.
Trim the whole other side of the door in the same manner that you trimmed this side and you should end up with a beautifully trimmed door.

Rob Abbott
Operations Manager
Village Builders Inc.