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How to Make a Window Cornice Box
- 1×6 boards
- You will need enough wood to cover the length of your cornice box plus 3 1/2″ for each side. If your valance is large, you want 3 1/2″ supports at least every 4 feet.
- 1/2″ electrical conduit
- 2 1/2″ corner braces
- You will need one for each end and support piece.
- 1 1/4″ wood screws
- 2 1/2″ wood screws
- I love my miter saw and use it for almost every woodworking project. This one is the one I have and it is inexpensive but has worked perfectly for me for the past 5 years. Since there are only a couple cuts, you can also do it with a hang saw, jig saw or circular saw too.
- Pipe cutter
- Nail gun with 1 1/4″ 16 gauge finishing nails
- Wood glue
- Stain or paint
- Optional: Kreg jig for joining 1×6 boards to make extra long valance
- Optional: Curtain clips and curtains
Cut your 1×6 board to the desired width of your rustic cornice box. I recommend extending your cornice at least 2-3″ past each side of your window. It will make the window look larger and allow the curtains to hang to the sides of the windows. If your valance is larger than your board (like ours), you can use the Kreg Jig to join two 1×6 boards together to create a long board.
Cut 2- 3 1/2″ pieces from the 1×6 for each end of the cornice box. If you cornice box is larger than 4′, cut a center support for at least every 4 feet. My DIY cornice box is 15′ and I used 3 center supports so they are every 3′.
Mark the center of each end board and center support. Drill hole through each of the center supports just large enough to slide the electrical conduit through. Drill a hole 1/2″ way through each end board.
Sand and stain (or paint) all the pieces of wood.
Attach the corner braces to the wall where you will be hanging the end pieces and center supports with the 2 1/2″ wood screws. They will create a little ledge off the wall. Make sure the screws are in the wall studs, or use heavy duty sheetrock anchors. These will be holding the weight of the cornice box and the curtains.
Secure one of the end pieces of the box to the corner brace with the 1 1/4″ wood screws so it is sitting on top of the L that is coming off the wall. Then you will want to secure any center braces. Because our valance was so large, I found it was actually easier to place the center supports on the electrical conduit before securing them to the wall because I wouldn’t have room to feed them through the secured supports.
Cut the conduit to the length of your cornice board, minus 3/4″. Because your conduit will only go into the end pieces 1/2 way. If you are using curtains, you want to add the curtain clips to the conduit before securing it between the ends and center supports (I evenly spaced mine between each center support).
Feed the conduit into the end and any center supports that are already secured to the walls. Cap off the other end with the end piece and attach it to the remaining corner brace.
Add wood glue to the front of each end piece and center support piece. Place the front of the cornice box on top of them and attach with 1 1/4″ 16 gauge nails. You could completely build the cornice box with the conduit inside before attaching it to the L corner braces if you want, but because of the size of ours, it was easier to build it on the wall this way.
Now that you know how to make a window cornice box, all you need to do is attach your curtains to the curtain clips and admire your work. Everyone that visits comments on how beautiful our DIY cornice box is and I love the way it is balancing out our problem window area.
If you loved this easy DIY, make sure to check out the rest of my DIY decor tutorials.