Easy DIY Cased Opening Trim Ideas
Easy DIY Cased Opening Trim Ideas
How to DIY a cased doorway or opening the easy way
Sometimes you just need a little extra something to make a space feel really grand and finished.
That was the “case” with this plain opening (see what I did there). This opening leads from our entryway into our dining room.
Since we are knee deep in renovating this entryway I figured now was a good time to add some trim to this opening.
Cased openings add architectural interest and draw the eye upwards making the room feel larger, plus they are just so darn fancy!
Casing an opening and casing a doorway are pretty much the same concept just on different scales. So this some cased opening tutorial can be used on both projects.
Here’s the opening we will be working on:
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Cased Opening Supplies:
- 1/4″ Smooth Plywood
- 1×4 Pine Board
- 1×2 Pine Board
- 1×6 Pine Board
- Chair Rail
- Ornate Molding/Trim Piece (optional)
How to Case an Opening
For this large opening I started by ripping 1/4″ plywood down to the width of the opening. These pieces will go on the inside of the cased opening.
If you don’t have a table saw you can have them rip the plywood down to size at the store or use a circular saw with a guide.
I sanded these plywood pieces with 220 grit sandpaper before installing them in the opening.
To install the plywood to the opening I used 1″ nails, you could also use adhesive, but I try to avoid applying adhesive directly onto walls.
After the opening was cased with the plywood I applied stainable wood filler to the nail holes and in the seams. Later I will sand these areas down with a 220 grit sanding block.
Cased Opening Trim
Now that the large opening is cased with plywood it’s time to move onto adding trim to the opening.
I am a huge fan of adding chunky trim to door openings and windows. Adding wide trim boards brings craftsman elements into the space and helps the door and window appear to be larger and grand.
For this cased opening I am adding a 1×4 pine board to the vertical side. This board sits on top of the 1×6 baseboard. I cut the 1×4 so that the top of the board meets the top of the opening.
I made sure the 1×4 was level and then used 2” nails to attach it to the wall.
Adding a Header to Cased Opening
The first trim piece to be added to the opening header is a 1×2 board flipped on its side. The 1×2 is cut to the size of the opening plus 4-1/2″. If the other end of my large opening ended at a wall I would have added another vertical 1×4 board on that side and cut the 1×2 to the size of the opening plus 8-1/2″. You want the 1×2 board to stick out a 1/2″ further than the vertical 1×4 board.
I used clamps to secure this piece once I had it level on top of the cased opening. At this point only the clamps are holding it in place.
On top of the 1×2 board I added a 1×6 header piece cut to the size of the cased opening plus the width of the vertical 1×4 board. These 1×6 pieces should be flush with the 1×4 trim pieces.
I used 2″ nails to secure the 1×6 header into studs after making sure it was level. Then I attached the 1×2 to the 1×6 board with nails from the bottom. Now you can remove the clamps.
After those two header pieces are attached it’s time to add the final top trim piece. I have used multiple wood variations for the final piece during past projects. You can check out a really fancy (but easy) stacked wood header configuration here!
Or you could also top the header with another 1×2 cut to the same length as the bottom 1×2 for a really classic look.
For this opening I went with an ornate piece of chair rail as the final piece. This method is great if you are comfortable making a few more cuts with a miter saw.
To cut this final piece I held the chair rail upright against the saw stop and made a 45 degree cut to the left. Then I moved the saw to the 45 degree mark on the other side. I slid the same piece of chair rail so the other end touched the blade and made the cut.
Finally I moved the saw to the 0 degree mark and measured in 3/4″ from the flat point of the angle cut I just made. The 3/4″ is to account for the width of the 1×6 header board (it will make for sense in a minute).
Cut a straight cut on that mark. This piece will be the return piece for the chair rail. I like to use hot glue to attach the return piece to the larger piece of chair rail before installing it.
Once the return piece is in place, I attach the chair rail directly onto the top of the 1×6 header board. I placed it about 1/2″ from the top of the 1×6 header and attached it with 2″ nails.
See how fancy the return end looks?
Adding Ornate Decorative Trim to Header
Normally this is the point where I start filling holes and painting or staining the new casing and trim. However I wanted this header to be a bit more of a statement.
So I added this pretty piece of ornate trim to the center of the 1×6 header piece.
I measured the 1×6 header board, found the center and attached the ornate trim with adhesive. I used painters tape to hold it in place while the adhesive dried.
It adds a little extra fancy to this cased opening don’t you think?
Finishing the Cased Opening Trim
Now that all the casing and trim is attached to the opening I used stainable wood filler to fill all the nail holes. I caulked all the places where the trim met the wall with regular paintable caulk.
I lightly sanded the filled holes with a 220 grit sanding block and wiped down the entire cased opening to remove the dust.
When we renovated the “Upper Room” a few months ago I stained the window trim and absolutely fell in love with the look!
So I knew I also wanted to stain this cased opening to also match our newly installed board and batten going up the staircase.
I went with Hickory Gel Stain by Varathane, it is the perfect deep, rich brown color. I started applying the stain with a 3″ stain brush and went back with a small craft paint brush to stain the intricate details on the ornate trim piece.
After the stain was dry I finished it off with a clear satin polyurethane.
DIY Cased Opening with Trim Reveal
It is absolutely amazing what a few pieces of wood can do for a large opening!
I am in deep love with how this cased opening turned out, it has a much better flow and feels so grand.
The stain color looks regal and I am so glad I decided to add that final fancy trim piece to the header.
Eventually when I makeover the dining room I will add the same trim to the other side of this opening but for now this project is complete!
It feels good to have another project complete in this staircase/entryway makeover. We are still waiting for the rest of the wood to arrive to finish the board and batten…
Let me know what you think about this DIY cased opening.
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