A window sill shelf can be built in a number of different ways, depending on the style of your window and the amount of work and effort you’re willing to put into the project. There are a couple of different ways to complete a window sill shelf, but they all have the same basic principles.
Remove the Old Window Sill
The easiest way to make a window sill shelf is to replace your current window sill with a piece of wood that increases the depth of the window sill. To remove your old window sill, use a pry bar or hammer and chisel to remove the trim and to carefully remove the old window sill. You can also remove the apron of the window sill because you’ll be using wall brackets for the shelf.
Build the New Window Sill Shelf
Measure the length and height of your old window sill. Your new window sill shelf will need to be the same length and height but have a greater depth. It’s up to you how deep you want the window sill shelf to be. Use a hand saw to cut the piece of wood for the window sill shelf to the proper dimensions. You can use a piece of scrap wood, such as an old tabletop or shelf, or you can purchase a piece of wood from a lumberyard. You’ll also need to purchase wall brackets that will support the weight of the shelf. The larger the shelf, the more supportive your wall brackets need to be.
Installing the Window Sill Shelf
When installing your window sill shelf and wall brackets, you don’t want to completely nail or screw everything in until you have all the pieces in the right places. Nail the window sill shelf partially using finishing nails, and use stud finders to find wall studs to attach the wall brackets. Don’t screw the wall brackets all the way in. Begin reattaching the trim, but don’t nail this in all the way either. Once you think you have everything lined up, use a level to make sure the shelf is even. When everything is in its place, you can secure all the nails and screws.
Finishing the Shelf
Once the nails are in place, use a nail set to sink them into the wood. Place the nail set on top of the nail head that is flush with the wood and hammer it down even further. Cover the nails with wood putty. If you want, you can sand down the wood and prime and paint the window sill shelf or do this before you reattach them to the window.