How to trim out windows and doors without a ton of cutting and different moulding pieces.
Finish nails for attaching to window jambs and longer nails for attaching to studs in walls
Wood filler for filling nail holes
Side casings are cut to interior height of windows + 1/2" (For 1/4" reveal on top and bottom. For no reveal at bottom for flush window sill, cut just 1/4" longer)
Header and aprons are cut to fit - see project plan below
4 - header and apron mitered returns - see project plan below
Please read through the entire plan and all comments before beginning this project. It is also advisable to review the Getting Started Section. Take all necessary precautions to build safely and smartly. Work on a clean level surface, free of imperfections or debris. Always use straight boards. Check for square after each step. Always predrill holes before attaching with screws. Use glue with finish nails for a stronger hold. Wipe excess glue off bare wood for stained projects, as dried glue will not take stain. Be safe, have fun, and ask for help if you need it. Good luck!
Start with your window, and remove any moulding until your window is flush to the wall. If you need to finish out the window jambs, you can read how we did that here.
Measure the interior height of the window.
Add 1/4" for the top reveal.
Add 1/4" more if you want the bottom of your window to have a reveal too.
This is the length of your side casings. Cut side casing.
Nail side casings to window jambs and to rough framing of window (behind drywall). We used 1" nails to nail casing to window jambs, and 2" nails to nail window casings to rough framing behind drywall, with an 18 gauge nailer.
The casings are attached with a 1/4" reveal - meaning they are not flush to the insides of the jamb, and instead, 1/4" of the jamb's front face is revealed. This is done because it is very difficult to get two edges perfectly aligned, and keep them aligned over time (think wood shrinking, house settling etc.) The revealed edge also provides and added layer, giving the window even more interest.
You can read more details about how we installed casing trim here.
For the headers, you have to use a moulding that has a base that is at least as wide as your casing to cover the casing. The wider top edge gives the window header the appearance of a crown moulding - without doing all the work. These mouldings come in different sizes - use a larger moulding for a more dramatic window.
With your casings installed, measure the outside dimensions of casing to casing. Measure the top and bottom and note.
Once the headers and aprons were cut, we fit on the windows.
We'll need to cut mitered returns to finish off the ends of the headers and aprons.
These are the mitered returns - they are basically the header moulding, cut at 0" long to a 45 degree bevel.
We used hot glue to glue the mitered returns to the ends of the headers and aprons.
We build all of the headers and aprons at once, and labeled the back sides to keep them from getting mixed up.
We also used wood filler to fill any cracks on the ends, sanded the ends, and then painted them on sawhorses. It's much easier to paint on the ground, then having to tape the headers off, and paint over your head.
Then the headers and aprons are nailed up, same as the casings.
Since the headers and aprons are already pre-painted, I just went and filled all nail holes with wood filler. Then I just had to paint the casings and touch up the headers.
We then siliconed any stubborn cracks/gaps.
You can read more about how we built the headers/aprons here.
We did the same with the door headers and closet headers. There were close to 30 headers in just this side, so being able to finish a header without multiple pieces of moulding was a HUGE timesaver.
It is always recommended to apply a test coat on a hidden area or scrap piece to ensure color evenness and adhesion. Use primer or wood conditioner as needed.