Marble Window Sills

A marble window sill is the finished stone ledge that caps the base of a window opening. It does the same job as a marble threshold — a durable, water-resistant stone surface where two materials meet — but it sits horizontally at the bottom of the window rather than underfoot in a doorway. Marble is the traditional choice because it shrugs off the condensation, sunlight and temperature swings that warp painted timber sills.

What size window sill do I need?

Measure the width of the window opening from jamb to jamb, then the depth from the inside face of the wall out to where you want the sill to finish. Most sills are cut a little longer than the opening so they project slightly past the reveal on each side, and deep enough to overhang the wall by around 1 inch.

Our sills are cut from the same slabs as our thresholds, in the same stones and finishes. If your opening is not a standard size — and window openings very often are not — it is cut to order. The method is the same one set out in our measuring guide.

Which marble should I choose?

White Carrara is the most popular: soft grey veining that suits almost any window frame. Calacatta Gold is bolder, with dramatic veins and warm gold tones. Crema Marfil is a warm cream that works with wood frames. Black Absolute granite gives a strong contemporary contrast against white trim, and is the most forgiving stone if the sill will take heavy sun.

Polished or honed?

Polished shows the veining vividly and wipes clean — the usual choice for a living room or bedroom window. Honed is a matte surface that hides water spots and hard-water marks, which makes it the safer choice above a kitchen sink or in a bathroom where the sill gets wet.

Window sill or threshold?

They are the same material and the same fabrication, and the terms are often used interchangeably in the trade. The practical difference is where the stone sits: a threshold or saddle goes in a doorway, underfoot, and usually needs a bevelled edge so people can walk over it. A window sill sits at the base of a window and normally wants a simple squared or lightly eased front edge, because nothing has to travel across it.

Need a size that is not listed here? Request a free custom quote — sills are cut to order in our Jersey City, NJ shop.