Osborne Builder's Studio: DIY Window Cornice Box
In this video we show you how to build a DIY window cornice box using Osborne's Crown Moulding! This project is an easy way to add a decorative touch to your existing windows and can be customized to fit your space. For more information on the parts used in this build, check out the links below!
Assembly Instructions
Overall Dimensions: 85 ⅜” x 7 ⅜” x 8”
What we used:
- Traditional Cabinet Crown Moulding (Part #74632)
- Brantley Panel Moulding (Part #893166)
1” x 8” x 96” Primed Lumber - x1
1” x 4” x 96” Primed Lumber - x1
1” x 2” x 96” Primed Lumber - x1
Other items needed:
| Miter Saw | Drill | Finish Nailer | 90° Drill Adapter (optional) |
Wood Glue | Wood Screws | Tape Measure | Paint |
| Wood Filler | Sander | Brush |
Instructions:
Step 1 - Measure the window
Take measurements of your window to determine the desired width of your cornice box.
Step 2 - Cut the lumber
- Create a bevel cut on each end of the 1” x 8” Primed Lumber using a miter/circular saw, which allows for a cleaner glue up.
Cut 2 side pieces from the same piece of 1” x 8” Primed Lumber
Note: The length chosen will determine how far the box sticks off of the wall. We chose a 5” side piece.
Step 3 - Attach the miters together
Add glue to the miters and tack them in place using a finish nailer or brad nailer.
Step 4 - Create a top piece
Add a top piece using 1” x 4” Primed Lumber, which will attach to the wall later. Use wood glue to attach. Secure with finish nailer or brad nailer.
Step 5 - Add base moulding
Add panel moulding to the bottom of the frame using Brantley Panel Moulding (Part #893166). Cut miters at each end to the length of the box. Add wood glue and place it on the bottom edge of the cornice box. Secure with finish nailer or brad nailer.
Step 6 - Add top moulding
Measure and cut the Traditional Cabinet Crown Moulding (Part #74632). Angle the moulding against the top and bottom fence of the miter saw, while making sure the top of the crown moulding is touching the base of your saw. Ensure the moulding is flush and even with the cornice box when attaching. Use wood glue and finish nailer to secure.
Step 7 - Get ready for installation
Add wood filler to the nail holes.
Sand for a smooth finish.
Add a coat of paint.
Step 8 - Create a wall mounting cleat
Use 1” x 2” Primed Lumber to attach to the wall to use as a mounting cleat to secure the cornice box. Center mounting strip to the center of the window.
Step 9 - Pre-drill
Before attaching the cornice box to the wall, pre-drill holes in the top of the box and counter sink wood screws slightly.
Step 10 - Attach the cornice box to the mounting strip
Mark center of mounting strip and cornice box. Place the cornice box on top of the mounting strip and tighten the wood screws. Drill screws on top of the cornice box into the mounting strip using the 90 degree drill adapter (if needed).
