Easy DIY Custom Window Trim

Earlier this year, our home received a much-needed update: new windows. With new windows (hallelujah), comes the need for updated trim.

I wanted a custom trim look but when I started to price out thick decorative trim, expenses added up quickly. 

Our home is pretty old which comes with unlevel surfaces and different measurements. I opted for this way of trimming for something different and to stay away from angled cuts. This was the first time hanging trim like this and it went up amazing.

HOW TO: I started by cutting a 1x4 pine board for the window sill/shelf. I measured my window width and added 10" for 5" on each side of the window. I used my Dremel to cut a quick and simple chunk out of the board for the window sill.

Once cut, I nailed the 1x4 sill board into place and moved forward with finishing the bottom half of the trimming. I then took my 1x4 length measurement- took 2" off the measurement and cut a 1x6 to that length. While you're at it- cut an optional decorative trim to the same length. 

I took my 1x6 board (cut to length), decorative trim and nailed those up underneath the 1x4 sill board. You should have 1" difference on both sides under your sill- as pictured.

Now, moving up the sides, I had to fix my window depth issues to run the vertical trim pieces flush with the wall. There was a 1.5-2" gap to fill from the window surface to the panelled wall (gotta love old homes). I used 1x2's to fill in around the inside of the window as shown here:

I took two 1x4's as my side trim pieces, cut them to length and nailed those up. I topped the window trim with a 1x2 (turned it belly side in and cut to the same length as the 1x6), nailed another 1x4 and topped the entire look with another 1x2. 

Did you follow all of that? Phew. Here's a better trim diagram if you're more of a visual kinda person.

We had 8 new windows installed and we just finished trimming all the windows out. I finished off the windows with caulking the seams and gaps. You could then stain your trim but I opted to paint them. I'll be finishing off ours with Benjamin Moore, White Dove (the perfect creamy white). 

I love how large and custom this trim feels. This was the first time hanging trim like this and I loved that I didn't have to make any angle cuts (especially with our odd, old home). I hope this trim inspires you for your home. There are so many different variations you could do, too! Happy trimming!

Hugs, Alyssa


  • Cathy

    Looks great! The play by play directions are great.

  • Paul Fisher

    Came out great !!!

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