How to Build a Window Box

A window box can enhance your home’s curb appeal and soften the window’s appearance.

Begin by measuring the width of the window to determine the size of the window box. Ours will extend to the full width of the window so we’re cutting two one-by-eights and one one-by-six to that dimension.

The one-by-six will form the bottom of the box and the one-by-eights will be the front and back walls.

The back wall is attached to the bottom in a 90-degree corner with wood glue and coated deck screws.

The angle of the front side will be dictated by the amount of taper on the end cap. Our end cap is made from a piece of one-by-eight that has one side tapered from five-and-a-half inches to four inches.

Position the side of this piece with two 90-degree cuts toward the back of the box so that the tapered edge is on the front with the narrow edge at the bottom of the box.

By gluing and screwing this piece into position, we establish the angle of the front taper so the front side can be attached to the assembly.
Another identically tapered piece can then be installed at the other end.

In the middle of the box, we’re securing a small piece of two-by-four to add extra strength before we drill drainage holes every few inches along the bottom.

The vertical cleats that will support the box and hold it off the wall of the house are made from one-by-fours.

We’re marking and cutting a radius on the bottom of our cleats for decorative purposes. Each cleat is made of two pieces: a larger piece that is four inches longer than the height of the box and a smaller four-inch piece that is glued and screwed on top of the longer one with the bottom edges flush with each other.

Once all of the parts are sanded, primed and painted, the cleats can be attached to the wall. The box sits on the lip of the cleat for vertical support and screws through the back of the box to tie it to the cleat.

The finished product is both functional and attractive.


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