DIY Window Trim - Add Character to Boring Windows

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Inside: Add your own DIY window trim using MDF. A quick and cheap update that adds lots of charm and character.

This is where our master bedroom started. Since then we have done several updates including stenciling the wall, installing new carpet, a new ceiling fan, new window treatments, new linens, and adding window trim.

Blinds attached to the outside of a window isn’t my favorite look.

I removed the ledge and bottom trim.

This is where we are now.

*This post contains some affiliate links for your convenience. Click here to read my full disclosure policy. *Before you get started make sure you have your Safety Gear. For this project, I recommend safety goggles, ear protection, and a P100 mask.

DIY window trim enhances the look of the room without having to spend a lot of money.

Let’s get started!

Check out this easy wall update instead of wallpaper: How to Stencil a Wall

TOOLS FOR DIY WINDOW TRIM

Tape measure
Chop saw or miter saw – I use this miter saw
Table saw or circular saw – I used a circular saw with this Kreg Rip Cutter
Jigsaw – I use this Rockwell Bladerunner
Sander or sandpaper 60 and 150 grit, I use this orbital sander
Level
Square
18G Brad nailer – I use this 18G Brad nailer
Small paintbrush
Paintbrush
Foam roller
Wood clamps

SUPPLIES FOR DIY WINDOW TRIM

1 – 8′ x 4′ x 3/4″ MDF
18G 1 1/2 inch Brad nails
Wood glue
Caulk
Primer – I used Kilz 2
White latex paint – I used Extra White from Sherwin Williams

CUTS FOR DIY WINDOW TRIM

I did the trim for two windows and used a little over half of the sheet of MDF. Your window sizes will vary from mine, but I have listed my cuts for one window below as a reference.

Even if you have the same windows in a room make sure to measure each window as the window openings can still be different sizes. Make sure to measure the length, width, and depth of your windows. For almost all my cuts I kept the width the same. I recommend cutting your pieces as you progress through the project. *It’s helpful to label your pieces especially if you are working on multiple windows.

1 – 3/4″ MDF at 66 3/4 x 3 1/4 inches (ledge) window sill depth 1 3/4 inch leaving a 3/4 inch overhang over the bottom piece and the side pieces
2 – 3/4″ MDF at 45 7/8 x 3 1/2 inches (sides)
1 – 3/4″ MDF at 65 1/4 x 3 1/2 inches (bottom)
1 – 3/4″ MDF at 66 3/4 x 3 1/2 inches (larger top piece)
2 – 3/4″ MDF at 66 3/4 x 1 1/2 inches (small top pieces)

STEPS TO MAKE THE DIY WINDOW TRIM

Step 1) Ledge – Cut your ledge piece longer than the width of your window and both side pieces leaving a 3/4″ overhang past the side pieces. I recommend leaving the length a little longer than needed to account for any errors. Then measure and cut out the ends of the ledge to fit in the bottom part of the window. To do this measure the depth of the window to make your corner cuts. For my windows, this was 1 3/4″.

Dry fit and cut as needed. Once you are happy with your fit then trim each end to size.

Prime and paint your ledge. I used a small paintbrush to paint the edges and a foam roller for the top.

Insert your ledge, check for level, and nail in place with 18G 1 1/2″ brad nails.

If your ledge isn’t level then add some shims.

Step 2) Sides – Measure your sides then cut, prime, paint, and nail like you did in the previous step.

The sides sit on top of the ledge and you will caulk later to fill in any gaps.

Step 3) Bottom – Measure the bottom piece. I made my bottom piece as long as the distance measured to the outer edge of the sides, being 3/4″ shorter than the ledge on each side. Prime, paint and attach with nails.

Step 4) Header – Measure the header to overhang 3/4″ over each side piece. I wanted the header to have more “bulk” than the rest of the window trims pieces. So there were three pieces to the top; a middle sandwiched between two smaller pieces. Turn the smaller top and bottom pieces on their sides so they jut out further than the middle piece. Attach the top and bottom pieces to the middle piece using wood glue and 18G 1 1/2″ brand nails. Use clamps to help with assembly.