Stooled cills include square “stools” at each end so brickwork can sit on them; they’re typically used with exposed brick façades. Slip (non‑stooled) cills sit between reveals and suit rendered or clad walls.
Durable Concrete Window Cills for Brick, Block and Rendered Walls
Precast concrete window cills provide a durable seating for window frames and direct rainwater away from the façade. Typical designs include a gentle outward fall and an underside drip channel to prevent water tracking on masonry; many products are made to BS 5642‑1 specifications for window sills in precast concrete and cast stone. In new openings, a cill is commonly paired with Concrete Lintels above to support the masonry span.
Cills are fitted beneath external windows across brickwork, blockwork, render and timber frame builds. To manage moisture correctly, installers typically bed the unit over a cavity tray/DPC and provide weep paths, practice reflected in independent installation guidance, so pairing with Damp Proof Course and Weep Vents helps shed water from the outer leaf. A front projection of around 50mm with the drip set clear of the wall is commonly advised to reduce staining.
Choices include stooled cills for exposed brickwork (square seats for the jamb masonry) and non‑stooled/slip cills that sit between reveals for rendered or clad finishes; common widths are 200mm and 250mm with multiple stock lengths. Many precast options are smooth faced and can be cut on site to length where stated by the supplier; joints are then pointed or sealed with a compatible compound. For bedding and making good, shop Ready Mixed Cement and weather‑resistant Sealants to complete the installation neatly.
Concrete Window Cills FAQ's
Guides commonly allow about 50mm front projection with a drip line set clear of the wall face to break capillary action and reduce staining.
Many precast cills can be trimmed to length where stated by the supplier—check the product details before cutting.
Stock ranges frequently include 200mm and 250mm widths across a selection of lengths for both stooled and non‑stooled profiles.
Yes. Many lintels are designed for single-skin and cavity wall applications. Always check span capacity and compatibility with the wall design.