What to measure
| Dimension | How it is determined |
|---|---|
| Length | window opening width including the reveal returns |
| Depth | from the frame plane to the wall |
| Overhang | how far the sill projects beyond the wall plane |
| Thickness | by agreement, based on span and support |
| Edges | chamfer, round, bullnose |
| Cut-outs | for corners, columns or services where needed |
Take exact dimensions on site after the window is installed: plastering and reveals can still change the geometry. Ordering from guessed sizes usually means cutting the finished piece on site.
Edges and junctions
The edge treatment is not only cosmetic. Assess edge shape and projection for the actual location and possible contact; a chamfer or rounded profile alone does not establish safety, and a bullnose closes the visible underside. Check whether the sill will project above a radiator and whether it restricts opening sashes.
We make window sills to exact sizes with edge treatment, chamfer, bullnose and service cut-outs. Installation is carried out by a separate contractor unless agreed in the order.
Frequently asked questions
When should a sill be ordered — before or after window installation?
After the windows are installed and the reveal geometry is clear, so dimensions match the actual opening.
Can the sill be made with an overhang for curtains?
Yes, the overhang is included in the dimensions in advance.
Which edge should be chosen?
It depends on how visible the edge is and whether people pass close by. A chamfer or round is more practical than a sharp square edge.
Explore interior products or send dimensions.
Sources and scope
- NIKA GRAN window sills — range and stated edge finishing.
- Natural Stone Institute: Care and Cleaning — stone care principles.
This is not an installation drawing: fixing method and opening preparation are set by the contractor.
Editorial clarification, 15 October 2026: general guidance does not replace checks of material, site condition or applicable local requirements.