How to Apply Trim Between Room Openings

If you are looking for a renovation project that is fairly easy to do, not very expensive, and will make your home dazzle, then consider applying a trim or casing to dress up the entry ways between your rooms.

First, gather your supplies. You are going to need the following:

Step Ladder

Circular Saw

Drill and Drill Bits

Miter Box


Wood Putty

Caulk gun


Paint Primer

Semi-gloss Paint in your color of choice for the trim

Paint Brush

Safety Goggles


Finish Nails

Nail Set

Tape Measure



Jamb Stock, flat and straight (1×6)

Tapered Wood Shims (just get a small portion)

Now it is time to get started. The first task you want to complete is to apply a paint primer to your jamb stock and molding. Allow to dry. If you purchase pre-primed jamb stock and molding, you can skip this step.

Paint your trim with the semi-gloss paint and allow to dry.

Next you want to check and see if your opening is square and plumb. If it isn’t, you will need to put the wood shims under your jambs. Use the shims to get your working surface level.

Measure where you will be inserting your jambs. When doing this and all measuring for the application of jambs and molding or trim, make sure you measure very accurately. Know too, that you can trim a too-long piece a lot more readily than you can fix a too-short piece, so take extra care to ensure you are not creating more work for yourself by an inaccurate measure. Allow the cuts for your jambs to be one-eighth of an inch larger than the width of how thick your wall is. Put on your safety goggles and make your cuts with a circular saw.

Put your jamb stocks on your cutting surface. Mark where your width will go and cut with a circular saw. Use the rip setting to do this. You will need three pieces.

Measure the length of your opening and cut a piece from the jamb. Insert wood shims on each end, if necessary to bring the piece level. Use your finish nails to secure the jamb.

Use the same technique as in the above step to apply the side jambs.

Measure where you need your casing or trim. Put a pencil in the end of a square and mark around the edge of your jam and then draw them out straight with the edge of your tape measure or square. Use your miter box to cut where the pencil lines are. Use finish nails to secure the side pieces of casing. Use a nail to put the edges into the framing (you need to go through the drywall).

Now you are going to put the top piece on. Miter cut the piece where your pieces will meet being very careful to get an accurate measure before doing so. Cut your casing and apply it with finish nails.

Use your nail set to put the nails below the surface. Fill all holes with caulk or wood putty. Sand where you need to and then apply touch up paint where applicable. You have now created a visually stunning passage way from one room to another. You can repeat this process for every entryway in your home if you would like to, for a very uniform and cohesive style. You can paint the trim to match the existing wall covering, or to contrast with it. You can also use a stained wood trim, if you prefer. You can use this tactic, now only for entrances into rooms, but also around any object you would like to permanently frame, such as a window or doorway (like perhaps a set of French doors).

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