Window sill
The term sill (or cill), refers to the lowest horizontal element of a structure or body. In the construction industry this most commonly relates to a window sill, or sometimes to the threshold of a door.
A window sill (or windowsill, sometimes referred to as a window ledge) may be formed by timber, stone, slate, brick and so on, and is located at the base of the window. It may provide structural support for the window, and on the exterior may be inclined and project beyond the surface of the wall to shed rainwater.
In the interior, window sills are commonly formed by timber, and provide a ‘shelf’ at the bottom of the window.
[edit] Related articles on Designing Buildings
Featured articles
Check out some of the best features and news from Designing Buildings as well as key stories from around the web.
Confronting competency, codes, capacity and costs.
The hidden risk in modern construction supply chains.
Construction Management, 10 June
24 months to 14: CITB launches accelerated apprenticeships.
Bridging the gap between clients and contractors
Concerns remain around contractor quality, capability, and delivery.
Construction Management, 10 June.
Heat pumps beat boilers in new home tests.
Building Safety Act implementation in Wales
CIAT to host industry panel on 26 June.
New and updated CLC building safety guidance.
New UK National Buildings Database.
Building Safety Wiki Interviews
Chief executive of the British Woodworking Federation.
Planning condition discharge in England and Wales
A brief explanation from a building compliance expert, with further links.
Overheating guidance and tools for building designers
Guidance for dealing with element of building fabric control that have increasing importance.

















