Craftsman Window Trim – Easy How To 

Easy How to Craftsman Window Trim

If you’re like me and have a builder-basic house, you might have noticed that your windows came with nothing—no sill, no trim, just bare drywall. That’s exactly what I was dealing with! But don’t worry, it’s an easy fix, and I’m going to walk you through how to add a window sill to give your windows that polished, finished look. You can watch the videos here.

From this…

To this…

Shop the room here: You can find the materials I used on my Lowe’s storefront. (Please note that these are affiliate links, and I earn a small commission when you make a purchase through them. Your support is greatly appreciated!)

Materials You’ll Need:

• 1×3 Pine Board
• 1×2 Pine Board
• 1×4 Pine Board (Apron, sides, and middle part of the header)
• 1×6 Pine Board (Stool) 4.5 inches longer on each side
• Sherwin-Williams Pure White Semi-Gloss
• Wood filler: For filling holes and imperfections.
• Paintable caulk: To seal gaps and create a clean finish.
• Brad nails: Various sizes for different parts of the build.
• Painters Tape
• Paint roller
• Clamp
• Wood Glue

Tools You’ll Need:

• jig-saw
• Brad nailer: Makes assembly faster.
• Miter Saw
• Tape Measure
• Nail Punch
• Caulk Gun
• Safety Glasses

Step 1: Measure the Window & Sand

Start by measuring the width and depth of the inside window frame. I measured and built each window individually for the best fit.

Next, lightly sand the area where the window stool will sit using 220–grit sandpaper. This will smooth out any rough spots and help ensure the stool sits flat against the surface. Check that the area is level. If it’s not, use shims during installation to create a flat, even surface before attaching the stool.

Step 2: Install the Window Stool

The stool is the bottom shelf-like piece that sticks out under the window.

1. Cut your 1×6 board to the width of your window plus 4.5″ on each side. For example, my window measured 34.5″ wide, so I cut my board to 43.5″ long.
2. Next, mark 4.5″ in from each end of the board. Then, using the depth measurement of your window frame, mark the sections that need to be removed. These cutouts will allow the board to fit around the window opening while leaving an overhang on both sides. (see photo below)
3. Clamp the board down. Use a jigsaw to cut out the notches, then test fit the board.
4. Once you’re happy with the fit, check that the stool is level and secure it with brad nails. If the stool isn’t level, add a shim underneath to raise the low side. Don’t worry about any small gap created by the shim—the apron installed in the next step will cover it.

Step 3: Attach Trim to the Sides of the Window

1. Measure the height from the top of the window stool you just installed to the top of the drywall.
2. Cut two 1×4 boards to this length using a miter saw. (Mine were about 60″ long.)
3. Before attaching them, leave a 1/4″ reveal along the inside edge of the window frame. You can use a laser level to keep the reveal consistent, or simply measure and mark 1/4″ along the length of the window.
4. Once everything is lined up, attach the boards with brad nails.

Step 4: Cut and Level the Apron

The apron is the trim piece directly below the stool. This will align with the width of your window.

1. The two 1×4 boards that you just installed, measure the width of the two.
2. Cut the new 1×4 board to that length with a miter saw, or use a circular saw.
3. Line up with the vertical 1×4 boards above. (see photo below)
4. Check that it’s level.
5. Attach it with brad nails.

Step 5: Pre-build the Top Trim

Start with the 1×4 board and lay it flat.

Next, add the 1×2 boards to the top and bottom edges of the 1×4. Lay them on their sides and make sure each side overhangs the 1×4 by 7/8″.

Then place the 1×3 board on top to finish the layered look. It should also overhang the 1×2 by 7/8″ on each side to create that classic Craftsman detail.

Use wood glue between each layer, then clamp everything tightly so it holds while you work.

Once in place, secure each layer using 3/4″ brad nails.

Here’s my measurements for reference:

1×3 board: 45 3/4″

1×4 board: 42 1/4″

1×2 boards: 44″

Step 6: Attach the header to the wall

Mark 7/8″ in from each end of the 1×2 board. These marks will show you where to line it up over the 1×4 vertical boards.

You can see my pencil mark below on the right.

Step 7: Fill, Caulk, Tape, and Paint

Caulk any seams for a clean, seamless look. Finally, paint everything. I chose SW Pure White in semi-gloss to match my baseboards, but you can go with whatever color works best for your space.

You Did It!

Congratulations on giving your bare window some charm, you should be proud of yourself! Ready to dive into your next project? Let’s go!

You got this!

– Audra