Try This: DIY Your Own Window Trim


Our bedroom renovation has been coming along nicely, bit by bit, piece by piece. Dare I say … it might actually turn into a room we love to be in? Since I last shared our new windows with you, we’ve DIY-ed trim, a deep window sill, and checked ‘Our New View’ off the list! It’s come a long way (this room used to be a kitchen!). As of our last update, the windows were in, but bare bones:


We purposely chose three separate windows with the intention of adding thick, chunky trim between each pane. When purchasing the windows, the salesman tried to convince us to make things much easier by choosing one larger window with built-in dividers, and he almost had us—until we slept on the decision. I woke up promising Scott that it would be so, so worth it to do three windows, add thick trim between, and create a look that would feel as though it’s always been a part of our hundred-year-old (plus) house.

Creating the window trim took us several days—from purchasing the wood, to installing, caulking, and painting. Building trim is relatively simple as long as you give yourself time and muster the patience for the task! To date, we’ve trimmed close to ten windows in our home, with a handful still left to do. Today, I’m going to share our trickiest DIY trim to date—simply due to the fact that I insisted on those three separate windows! Here’s what we did to kick those windows into shape:

INSULATE. I’m going to skip how much wood we purchased and in what lengths because, of course, this will be different for everyone! I will, however, share how the different trim and wood panels break down (in a minute), but first things first: it’s important to insulate. We used a bottle of spray foam we picked up at the hardware store, and Scott squeezed a thin line of foam around each window, completely blocking any cold air from passing through. Tip: In the meantime, I applied two coats of white semi-gloss paint to all of our loose wood pieces and trim. It’s not necessary, but I do find that it saves time (and sanity) once it has been installed.


MEASURE YOUR WINDOW SILL. For the sill, we used a 1″ x 8″ pine board—long enough to accommodate all three windows, the width of the side trim, and 1″ overhang on each side. In our case, this came to just over 10′ long! Measuring the sill is always the most difficult math of the entire process, but don’t stress because there is some flexibility once it comes time to caulk. We drew directly onto the board to show where we’d need to cut off the excess to allow for the sill to sit into each window.


CUT THE SILL. We used a jigsaw to notch out the sill where it needed to be trimmed back. We always err on the side of “too heavy,” so we can make another cut if we need more room for the wood to sit properly! With a board as long as ours, we did have to make several cuts—some here, some there—but we got it as close as we could.


SECURE THE SILL. We applied a line of construction adhesive under the sill and we secured it further with 2″ wood screws—about 3-4 screws per window. As Scott screwed, I pushed and pulled the wood to settle properly, which is really only a concern if the sill is as long as ours!


LEVEL ALONG THE WAY. There may be times where you’ll need to shim from underneath the sill. Not only do you want it to be level from left to right, but you want to make sure it’s sitting level from front to back, too.


CREATE YOUR WINDOW CASING. With the hardest part behind us, we moved on to casing the windows! This step hides the 2x4s from construction, as well as any overflow insulation (although you’ll still want to cut back any parts that foamed over on the heavy side). We used 1″ x 4″ pine boards and secured them with our pneumatic nail gun. No fancy cuts needed—just straight lines!


INSTALL THE FRONT-FACING TRIM. The inside window casing should sit flush with the wall, as it gets capped with another pine piece to finish it off! We used 1″ x 6″ pine boards for this, which leaves the smallest ridge (less than 1/4″) for caulk to sit. This trim only sits as tall as the windows themselves.


INSTALL THE DECORATIVE TRIM. From there, we continued on with the decorative trim, starting on the outermost sides, and continuing above (the header) and finally, below (the apron). Here’s how ours look:


Above: 1) Decorative side trim  2) Pine board window sill  3) Same as #1, used as an apron


Above: 4) Brick molding  5) 1″ x 6″ pine board   6) Pine stop

The best part of making your own trim is creating whatever you’d like! The above decisions we made match the choices we used throughout the rest of our home—it’s a look we like for the age of our home. If you spend some time in the trim and molding aisles at the hardware store, I encourage you to play around with different pieces and build upon them to achieve a style you love.

SPACKLE. With the wood cutting and installing complete, we went back around the entire window with spackling paste. This covers every nail and screw hole on the surface of the trim. Once the spackle dried, I went back around and sanded things smooth with 220 grit sandpaper.


CAULK. You probably noticed visible gaps where trim meets trim. That’s okay! This is where caulk comes to the rescue, as it fills in all those unsightly areas. I used white, paintable latex caulk (paintable is the operative word!), and after applying a thin bead to every edge, corner and entire perimeter, I used my finer to smooth it out. Tip: Work in small sections so the caulk doesn’t begin to ‘skin’, and always dip your smoothing finger in water. The water helps the caulk stick to the window and not to you!

YBH-0127 YBH-0128

Below, this is after caulk, but before paint. Already a huge difference!


FINALLY, PAINT. Because I already prepped the wood with a couple coats of semi-gloss paint, all I needed to do was carefully cut in around the windows and every edge (to cover all the caulk) and touch up the spackled areas. However, because the window sill will receive the most abuse, I applied two extra coats of paint. Our kitties will use this ledge as a perch, looking down on their so-called kingdom (I love that visual), plus I wouldn’t mind putting a plant or two in the window.


And done! The results are well worth the steps and days a job this size takes. Of course, it’s always more satisfying when we can step back in time to see how this wall looked at the end of last year, right before we began the window installation:


And now! Aah. Much, much better.


We’re planning to add shades so we can get some sleep (mornings have never been brighter, I’ll say that much), and I’ll be back to share what we chose and how they look—that is, once we make that decision ourselves! In the meantime, happy DIY-ing!

For more fun info on Kim’s renovating, check out her blog Yellow Brick Home.

Get Ready, Get Set, Create – with Bali! There are so many options to explore. . .So many colors, fabrics, styles, and features. . . so much potential for bringing a little zing into a room, or injecting your style into a whole house. So . . .where do you start? Start here. With Bali. 

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