Tom Shafer

Where pies cool: window sill or window stool?

July 03, 2013

What most people think of as the window sill -- the place where Grandma grew her African violets and Auntie Em left her pies to cool -- is actually the window stool.

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window stool

The window sill is the bottom horizontal portion of the window. On a wood window this is a thick piece of wood, shaped to a slope of about 7 degrees, the purpose of which is to move water away from the bottom of the window sash where it can collect and leak into your home.

Window sills

sloped window sill

While most sills are sloped, they also can be flat. Sliding windows, for example, have flat sills and a section of track on the sill upon which the sash slides. The track is open at the ends to channel water to the sill below. The sill, which is flat, can collect water, but it drains almost immediately by means of weep holes.

flat window sill

Vinyl replacement windows are built in a similar fashion. In order to make assembly easier, many vinyl windows use the same extrusion profile for the head (top), the jambs (sides) and the sill. Like sliders they have an upper piece in the sill into which the window closes. Water drains, as with the slider, via weep holes in the sill.

Window stools

The stool is a part of the window that is inside the house, not outside. It is flat and extends from the bottom rail of a sash inward. While there is no standard width for a sill, the stool -- at least in older homes, -- was usually three to four inches wide.

traditional window stool

Stools can be made from a number of different materials. The most common is wood that is either stained or painted to match the casing trim around the window. Marble or synthetic marble are popular, too. Used mostly in climates where condensation on windows may occur, marble does not stain from water the way wood can.

window stool

The photo directly above shows a ceramic tile stool. The home owner had the stool tiled so potted plants could be watered and left there without discoloring the stool. The wall was thick, which allowed room for a 7-inch stool -- plenty of width for the African violets.

Remember -- the sill is part of the window itself. The stool is not part of the window, and it's inside the house -- just in case someone gives you a pop quiz.

About the Author

Tom Shafer has decades of experience in window sales, marketing and product development. He's worked closely with window design engineers in testing, design, and building code interpretation. Past employers include United Windows and Doors and Norandex, MI Windows. He currently works at a home improvement retailer.

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