A window board is the flat internal shelf that finishes off the bottom of a window inside your home. It is the ledge you rest a plant on or lean against to look out. Its job is partly practical and partly about looks: it covers the gap where the frame meets the wall and gives the window a tidy, finished edge. Here is what a window board is, what it does, and how it differs from the sill.
When a window is fitted into a wall, there is a gap between the bottom of the frame and the inside face of the wall below. The window board caps that gap. It runs along the inside bottom edge of the window, sitting on the wall and tucking under the frame, so you get a clean surface instead of a rough opening.
Most people call it a window board, though some say inside sill or internal cill. Whatever the name, it is the bit you see and touch inside the room.
A window board earns its place in a few ways:
It is a simple part, but a room with no window board, or a tired one, always looks unfinished.
This is the question that trips people up, so let us be clear.
In everyday chat people use "sill" for both, which is fine, but on a quote or a plan the window board is the inside piece. If you want the outside part explained, our guide to window sills covers that side.
The material affects the look, the cost and the upkeep:
If you are having new windows fitted, the window board usually comes as part of the job, matched to the frame. Our uPVC window range includes board options, and for a crisper modern edge our aluminium windows pair with slim internal finishes too.
A window board should sit level, be well supported along its length, and be sealed neatly where it meets the frame and the wall. A small bead of sealant along the back edge stops draughts and keeps condensation from creeping behind it. Once it is in, it is usually painted or left in its factory finish, then the architrave and skirting tie it into the rest of the room.
If a board is loose, lifting or water-marked, it drags the whole window down visually and can let in a draught. That is worth sorting, and it rarely means new windows.
Signs a window board has had its day include swelling or soft spots on MDF, peeling paint on timber, staining from long-term condensation, or a board that has come away from the wall. Sometimes a clean, reseal and repaint brings it back. Other times, especially where damp has got into the board, it is better renewed.
If the window itself is fine and it is only the board that has gone, you do not need a full replacement. Our team can sort this as part of general window repairs across York, so it is worth a quick chat before assuming the worst.
The window board is the internal shelf inside the room, there to finish the reveal and give you a ledge. The window sill, or cill, more often refers to the external part that sheds rainwater. People use both terms loosely, but on a quote the board is the inside piece.
uPVC is the most popular for its low upkeep and wipe-clean surface, especially in kitchens and bathrooms. Painted MDF or timber suits homes where you want the board to match trim, and solid timber fits period properties.
You do not strictly need one, but without it the inside of the window looks unfinished and the wall below is exposed to knocks and condensation. Nearly all fitted windows have one for a neat, practical finish.
Usually long-term condensation or damp getting into an MDF or timber board. A wipeable, well-sealed board copes far better. If it has swollen or stained, it often needs replacing rather than just repainting.
Yes, in most cases. If the frame and glass are sound, the board can be swapped on its own. A quick look will confirm whether a repair or a new board is the right call.
Want to see how the finish comes together across a whole window? Download our latest brochure for styles and materials, or request a free quote and we will come and take a look.