Anatomy of Trim

We started the trim in the on-going master bath project with a sheet of MDF. Chad had an employee at the Home Depot cut the sheet into long strips - 4 of them 4 inches wide and 3 of them 8 inches wide. He built our trim from there by using the existing original trim throughout the upstairs as a guide. Here were his steps:

1. Plinth Blocks.
These needed to be a little thicker than the door casing and baseboard, so he cut a piece of luan the exact size as the plinth blocks and used it as a backing. This gave him about an extra 1/8 to 1/4 inch thickness. He started with a rectangle (4" by about 12") of MDF backed by the luan, then routed the top edge of the MDF with a round-over bit.

2. Side Door Casing.
For these he used the 4 inch wide strips of MDF and routed both of the long sides with a round-over bit. It was fastened just outside of the inside door jamb edge so caulk can be used to fill the seams.




3. Header.
The header is two pieces - first a thin strip of wood rounded on all sides that protrudes slightly past the casing in all directions. Above that is a 6 inch wide piece of MDF that is the same width as the door casings.

4. Crown.
In order to attach the crown and keep it solidly in place, Chad laid a 1-by piece of wood across the MDF header. He ripped this through the table saw, beveling the edge cut at the same angle and position the crown would make with the ceiling (if there were a ceiling to attach it to). This gave him the opportunity to fasten the bottom of the crown to the MDF piece, and the top of the crown to the 1-by piece. Even the small outside corner pieces were attached in the same way.

5. Baseboard.
I was able to get a router bit profile that closely matches the trim that was already in the bathroom. Chad routed the 8-inch wide pieces with this bit to create the baseboard. This was added on both sides of each closet door and on the long wall where the vanity will be.

I have filled nail holes and the plinth block/luan edges with wood putty, and caulked all of the seams. It has a coat of primer and is waiting on two coats of white paint to match the original trim.