Add a window sill to an existing window?

[Stephen Tashiro]

What's a good way to add a window sill to an existing window?

On the window in question, the sill (such as it is) does not extend all the way to the face of the drywall. The drywall around the edge of the window was shaved down and molding was put over it at an angle. I'll like to remodel the situation so the window has a sill that extends several inches past the face of the drywall.473777473778

[Kevin Jenness]

Mill a piece of stock 1" x 2 1/2", 1 1/8" longer than the outside dimension of the side casing. Bullnose the front and ends and scribe/notch the horns so the piece meets the drywall and existing bottom jamb. Fasten to the jamb with nails or trim screws and glue. Add an apron whose ends line up with the casings.

[Dave Roock]

You could also tear out the existing too short sill and replace with a new sill piece - possibly one you create out of wood of choice.

[Lee Schierer]

You could also tear out the existing too short sill and replace with a new sill piece - possibly one you create out of wood of choice.

I did exactly that when we remodeled our family/Office room. The walls weren't plumb but the window was so I had to taper the side jambs top to bottom to keep the outside edge flush with the drywall. Once the trim was added, you have to look really close to see the taper.

[Tom M King]

A window sill is the outside part that has a slope to it. The horizontal piece on the inside is a window stool.

I would take that piece out, and make a whole new piece. Opposing wedges underneath the stool, under the jambs, can force it up to fit tightly again.

If those are jamb extensions, instead of the jambs, I'd replace those too, and redo the trim. It's not unusual at all to have to make tapered jamb extensions. I never bought the stock jamb extensions.

[Dave Roock]

Using a sawzall you can somewhat easily cut that out of there - a sharp chisel can get the last portion near window. As far as a new sill/stool , one option would be the ready made stair tread products at HD, Lowes, etc. Many different styles & wood types, the stair treads already have the rounded over bullnose edge - all you would have to do is cut to length & possibly make a couple cuts to slightly overlap at sides. Envision that new oak window sill/stool.

[John TenEyck]

What Tom said; that's the stool not the sill. The width should be such that the horns extend beyond the casing by the thickness of the stool; so if the stool is 7/8" thick it should project beyond the casing by 7/8".


John