Concrete windowsills: what size, what cost, who fits one?

A concrete windowsill is made to the length and depth of your reveal, so an odd size isn't a problem. Prices start from £120 in the shop, and the page shows the exact price as you set the size.

How much does a concrete windowsill cost?

Sills start from £120 in the shop. A sill is priced by its size and thickness, so a shorter, narrower one costs less and a deeper or thicker one costs more. Our designer updates the price as you set the length and depth.

Each sill is made to order, so you're paying for your own size, and nobody is cutting yours down from a stock piece.

What size can you get?

Any size you give us. A stock sill comes in a few lengths, and you cut it down. Ours is cast to your measurements. A deep reveal in an old sash window gets a broad flat ledge for plants and books. A narrow modern one gets a slim sill that fits it exactly.

You give us the length and the depth, and we confirm the thickness. Measure the reveal at both ends, because old walls are rarely square.

How heavy is a concrete sill?

At 30mm, concrete weighs about 70kg per square metre. That's no heavier than granite at about 80kg or quartz at about 72kg. A sill covers a small area, so it's a far lighter job than a worktop, and a longer or deeper one weighs more in proportion.

Who fits it?

Your builder or fitter. We make the concrete and work alongside whoever is doing your window, and we supply anywhere on the UK mainland.

Whoever fits it, send us a photo of the support before the sill goes on, and in return you get five years on the making. If a fault comes from how we cast it, we remake it in year one and repair it to year five.

Will it cope with plants and a wet kitchen window?

Yes. The seal is SureCrete XS-327, a two-part, water-based hybrid polyurethane, put on as a prime coat and two coats. Water beads on it, and the maker rates it stain resistant to most household chemicals and food. It's UV stable too, so a sill in a sunny window keeps its colour.

A sealed concrete sill takes a wet plant pot without the rot you'd get from timber, so you can wipe up a spill and carry on. If a patch of seal ever wears, it can be lightly sanded and recoated in place.

Why choose concrete for a sill?

A window sill takes sun, condensation and the odd watering can. A sealed concrete one shrugs that off, and it won't rot or flake as timber can. It's also a shelf. The same piece works as a shelf, so the deep ledge in a thick wall earns its keep.

Can it match your worktop?

Yes. A sill, a shelf and an upstand can share the worktop's colour and finish, so the window and the kitchen read as one. The colour is in the concrete itself, not painted on.

How can you check the colour first?

Ask for a sample. It's free, and the colour you hold is the colour you get. Put one on the windowsill you're replacing and look at it in daylight. Order your free samples and see it in your own light.