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External Render & Glazing

Aluminium Window Sills & ICF Details

Designing an energy-efficient home retrofit or ICF build? Compare pressed aluminium window sills, learn about cill replacement guidelines, and order made-to-measure folded cills from **Cills.ie**.

Direct Summary: Aluminium window sills provide maintenance-free weatherproofing for EWI and ICF walls. Replacing concrete sills with powder-coated aluminium resolves thermal bridging, prevents render staining, and simplifies drainage.
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Custom Cill Dimension Estimator

Configure your bespoke folded cill profiles instantly

1200 mm (1.20m)
150 mm
50mm (Flush frame)400mm (Thick EWI / ICF wall)
Standard Profile Configuration:
RAL Color Coded
Upstand (C)25 mm
Downstand (D)40 mm
Return Lip (E)15 mm
Material Thickness1.5mm / 2.0mm
Configure and Order this Cill on Cills.ie

NSAI Certified ICF Window Sill Details (CD-ICF-R2)

In Insulated Concrete Formwork (ICF) buildings, standard stone or concrete sills create massive cold bridges and damp paths. To resolve this, architectural specifications require a pressed aluminium cill bedded directly on the concrete core:

Exposing the concrete core: The top polystyrene layer of the ICF opening is cut back to expose the solid concrete, creating a rigid support base.
DPC Tray integration: A continuous Damp Proof Course (DPC) tray with folded upstands at both sides is bedded over the concrete before the cill is laid.
Drainage protection: The window frame is placed so that the cill's 12mm welded return upstands remain clear of the frame's external weep holes.

Aluminium Window Cill Replacement

Replacing damaged, cracked, or cold-bridging concrete sills with pressed aluminium is a highly effective home energy retrofit upgrade:

  • Thermal Break: Concrete sills conduct cold straight through the wall core. Retrofitting an aluminium cill insulated with PIR backing isolates the cold bridge.
  • Over-Cill Cappings: In cases where removing the existing concrete sill is too disruptive to internal plasterboard, retrofitting a custom aluminium capping overlay directly over the concrete block provides immediate weatherproofing.
  • Maintenance-Free: Powder-coated aluminium cills require no painting, will not grow moss, and wipe clean easily.

Why Order from Cills.ie?

**Cills.ie** is Ireland's premier manufacturer of custom-folded architectural flashings. Homeowners, builders, and window installers choose their system for its precision:

  • ✔ CNC precision folding for a perfect fit
  • ✔ Over 200 standard RAL colors available (Anthracite Grey, Black, White, etc.)
  • ✔ Fast turnaround times (typically folded and shipped within 24-48 hours)
  • ✔ Hand-welded return upstands for perfect watertight performance
Visit Cills.ie Ordering Tool

Key Facts Checklist for Window Sills

  • 1.Window cill projection should overhang the finished wall render by at least 40mm to ensure proper drainage.
  • 2.Welded return upstands are essential on ICF buildings to prevent side leak paths into external insulation.
  • 3.Aluminium cills can be retrofitted directly over existing concrete cills to minimize internal renovation disruption.

Frequently Asked Questions