DIY Danielle


Window casing on the interior of the house adds a decorative touch. I'll show you how I added it to my she shed.


– AZEK Trim White PVC Traditional Trim – Scrap 3/4″ plywood – Ryobi Brad Nailer – Level – Safety Gear: Quality Mask  – Shims – Caulk: paintable – Wood glue – Miter saw – Spray foam insulation

STEP 1. Spray Foam any Gaps

The first thing you want to do is use spray foam insulation. Once it dries, cut away any excess pieces that might get in the way of the casing.

STEP 2. Install the Window Jamb

Now you need to add a window jamb around the whole interior of the window.  Measure the depth, height, and width of the area you need to add the jamb to.

Tips for Adding Window Jamb

Make sure it is level, then adjust it if needed. Use wood glue and a nail gun to attach the jamb. Next measure a piece for the head jamb, and the side jambs.

STEP 4. Cut the Window Casing

You can use primed wood to save a step. Cut the bottom casing piece slightly wider than it would be with the side casings on. Make sure it is level and even with or above the bottom jamb.

STEP 5. Install the Window Casing

Attach the trim using a brad nailer. Make sure the center of the trim piece matches the center of the window.

STEP 6. Angle the Casing

We made the top casing angled. We repeated the angle for both sides, and for all of the window headers. Attach with the brad nailer.

STEP 7. Patch Holes and Tape

Patch any holes with paintable caulk. Once dry, tape around the window casing. Then prime the unfinished areas.

STEP 8. Paint the Trim

I went with a unique look and used dark gray for the casing, with the jamb pieces of the window painted pink to match my couch.

Enjoy your beautiful window casing!

I'm so happy with how the window casing turned out! The 2 tone really gives a unique look.


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Danielle Pientka

Danielle is a DIY/craft/sewing blogger on She loves to write about projects that she makes for her small farm, her children, and her home.