Easy DIY Window Trim

Sometimes projects look great in your head then just don’t translate into reality, but this DIY window trim is not one of those projects. It took only one day to complete, used minimal materials and tools, and made the window itself look bigger and more high-end, even though we actually didn’t touch it at all.

We’ve been working on a mini refresh of our daughter’s room now she’s in a big girl toddler bed (that she’s been in for more than six months now, whoops) and her room was the perfect place to give the idea a test run and paint it a fun kid room color. So, I sketched up an idea for how it would look and figured it out as I went from there.

We’re now planning to do the same thing to just about every window because it makes such a difference! So, here’s how to make your own DIY window trim for an easy weekend room upgrade.

DIY window trim tools & materials

Tools

• Jigsaw
• Miter saw (or have the hardware store cut your pieces if you don’t own a saw)
• Brad nailer and 1.25” nails

Materials

• Primed MDF pieces (take measurements for your window sizing below)
  • 1×2
  • 1×3
  • 1×4
  • 1×6
• Caulk
• Spackle

Renovation Roadmap — DIY Project Planning Guide

How to make the cuts

We have weird-shaped windows so I won’t give our specific measurements but let’s lay out how to measure and cut each of the pieces.

Starting with the window ledge, this piece will end up looking like a rectangle that has two notched out corners.

To make that cut, measure the width of your window and the depth of your window casing and transfer those onto the 1×6 for the notched part, and follow the diagram below for the rest of the piece.

Note: The 1.25” is universal because that’s to account for the ledge piece extending out beyond the 0.75-inch pieces of MDF that will go above and below it. The window width plus 5” is also universal because that extra 5” is to ensure the piece extends as far as the 1×3 vertical MDF pieces will!

Next, the vertical 1×3 pieces. Measure the height of your window opening and subtract 0.75”. Make two cuts at that length.

Cut two pieces of 1×4 at the same length as your outer window ledge piece (the window width plus 5”), and two 1×2 pieces at one inch longer than the 1x4s are cut.

Assembling the DIY window trim

Put the window ledge in place (if it’s a tight fit use a mallet to softly tap it into place) and use your brad nailer to shoot 1.25” nails along the length of the piece until it feels secure. Line the 1×3 pieces upright on each side of the window, making sure they’re flush with the inner window opening before nailing in place.

Take one of the 1×2 pieces and lay it sideways so it goes across the very top of the 1x3s and sits flush with the upper window opening, then nail that into place too.

Repeat with one of the 1×4 pieces centered above the 1×2, and then the last 1×2 on its side again on top of the 1×4.
Lastly, take the second 1×4 piece and nail it into place underneath the window ledge, making sure it’s centered.

Finishing touches

Spackle over all the nail holes and caulk each of the seams. It’s tedious, yes, but makes such a big difference in the final look of the project! Then all that’s left is to paint and you’re done.

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