DIY Window Trim

Painted DIY window trim with bamboo blinds

Adding DIY window trim to windows in a room is one of the most easiest, fastest, and affordable ways to add beautiful character to a room. I’m super excited to show you how to trim a window with a beautiful, classic style trim!

We’ve been working on transforming our living room into a cozy, stylish space that we love. Windows can really be a great architectural focal point in a room. However, the original builder grade windows in our living room were significantly lacking any kind of wow factor or character:

boring builder grade windows before adding custom window trim

But now, they look awesome!

Double windows transformed with DIY window trim

This isn’t the first time we’ve completed DIY window trim. In our last house, I showed how we updated window trim by removing the old trim and adding a simple farmhouse style window trim. Although, I really like that style, this time around I wanted to do a super timeless, character filled window trim style. And I LOVE it!!!

Another big difference between our window trim in this tutorial and my previous tutorial on installing window trim is that this time around we totally replaced the window sill with a custom cut window sill. Check out the tutorial and video below for details!

Note, this post contains some affiliate links. For more info see my disclosures here.

DIY Window Trim


  • (4) 1x4s @ 8ft and (1) 1×4 @ 6ft***
  • (4) 1x2s @ 8ft and (1) 1×2 @ 6ft
  • (1) 1×6 @ 8ft (for window sills)
  • (1) 1×3 @ 8ft (for bottom of window trim)
  • (1) stop window molding @ 8ft (for bottom of window trim)
  • 2″ brad nails
  • Spackle
  • Primer
  • Paintable Caulk
  • Paint (I used Simply White by Benjamin Moore in Semi-Gloss)


***Note, the amount of wood you will need depends on the measurements of your window. I’ve listed the amount of wood that I used for my two 60″ tall x 31″ wide windows. Make sure to pick straight boards!

1. Remove old window sill and trim

Since my original window sill was really short on the edges and not wide enough for side window trim, I had to remove it.

Remove the old window sill and trim by first scoring the caulk line edges with a utility knife or similar tool.

Removing old window sill by starting with utility knife to score the the caulk line edges

Then, pry it up and off with a prybar and hammer.

Remove old window sill with hammer and prybar

Removing old window sill

2. Create new window sill

For the new window sill, I used a 1×6 board which was deep enough for my window and extended out about 2 1/4″ past my window wall frame. Make sure to measure your current window sill depth to ensure a 1×6 will fit as well.

Measure the width of your window opening and add 10 1/2″ as we need 5 1/4″ overhang on each side. Using a miter saw, cut your 1×6 board to size for your new window sill. My window opening measures 31″ so I cut my 1×6 board to 41 1/2″ long.

Next, to create the L shape cut out for the window sill, mark 5 1/4″ in from each side of the board.

To create the L shape cut out for the window sill, mark 5 1/4

Then, measure the depth of the old window sill cut and mark that measurement perpendicular to the first mark to create the L shape cut out marks. Make sure to measure the depth on each side of the old window sill as it may vary from one side to the other.

measuring old window sill for new window sill cuts

new window sill board marked for cutting

Use a dremel tool or jig saw and cut out the L shape out of the wood to create the two window sill edges.

cutting new window sill edges with Dremel tool for DIY window trim

There was still some wood in the corner of our cut out which we used a chisel to remove.

chiseling window sill edges

3. Install the new window sill

Put the new window sill in place and make sure it fits. It’s ok if there is a little bit of a gap between the wood and wall as the small gaps will be caulked.

installing new window sill

Secure the window sill with 2″ brad nails and a brad nailer.

installing new window sill with brad nailer

4. Add the 1×4 DIY window trim to the window sides and top

Measure the length of the window frame opening on both sides. Cut the 1x4s to size for these side pieces. Then, install them on the left and right side of the window with brad nails.Add the 1x4 DIY window trim to the window sides

Now measure the distance from the end of the left 1×4 to the end of the right 1×4 and cut another 1×4 piece to this size to create the top window trim. Secure in place with brad nails. Note, we had to use a screw into the stud on the right side of the top board since the wall area was uneven.

Add the 1x4 DIY window trim to the window top

5. Add the 1×2 trim to the window sides and top

Repeat the steps in step 4 above, except make your measurements for around the 1x4s. When installing the 1x2s next to the 1x4s, turn the 1×2 pieces on their sides and secure the brad nails through them into the 1x4s instead of the wall.

use a brad nailer for side 1x2 window trim installation

how to trim a window with wood

6. Add the base window trim pieces

Measure the distance from the left 1×2 piece edge to the right 1×2 edge. Cut the 1×3 and stop window molding piece to this size. Install the 1×3 first, centered under the window sill, then install the stop window molding piece on top.

Note, we cut our base pieces a little too short as you can see in the photo below, but we did it correctly for our 2nd window.

Base trim added below window

Now the window is fully trimmed out and should look similar to this:

DIY window trim added to window and ready for paint

7. Caulk, fill holes, prime, and paint!

Alrighty, last step! Caulk all the gaps and seams. Fill the nail holes (and any wood knot holes) with a lightweight spackle, allow it to dry, then lightly sand those fillings so they are smooth.

Next, prime the wood. Add a second coat of primer over the wood knots. Finally, add 2-3 coats of paint and you are all finished!!!

how to trim a window

How awesome does this DIY window trim look?! I absolutely love it, it’s so classic and has totally transformed our living room wall, giving the space so much character and coziness! I just sit on the couch and stare at it ha!

I hope this how to trim a window tutorial was easy to follow and helps you with your own window transformation! I’d love to see photos of your project! Feel free to share with me on Instagram and Facebook!


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6 thoughts on “DIY Window Trim

  1. I’m currently trying to figure out how to coordinate window and door trims. I like the trim you did on the window. Did you do the same around your doors?

    1. Thanks! I actually didn’t since we liked the trim we already had on our doors but we did paint them all the same colors so it’s cohesive. You could definitely do this on doors though too!

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