Standard Straight Cill Profile
The standard straight cill is the workhorse of Irish residential construction. A flat top surface with a 5 to 10 degree internal slope for drainage, a 50 to 75mm front projection, and a 20 to 40mm rear upstand hidden behind the window frame. Available in 1.5mm, 2mm, and 2.5mm aluminium thickness, with 2mm being the standard specification for most projects. Maximum length per piece is 2,000mm before mitred joints are required. Typical applications include new build estates, standard window openings up to 2m wide, and any retrofit where the wall thickness has not changed. The standard profile suits anywhere the wall face is no more than 100mm proud of the original window frame. If your insulation depth exceeds 100mm, specify the EWI profile instead.
Bay Window Cill Profile
Bay window cills are multi segment folded aluminium pieces that follow the bay angle. We design these in the app by entering the bay angle (commonly 30, 45, 60, or 90 degrees) and the segment lengths. The cill is fabricated as a single welded piece with seamless mitred joints, so it arrives in one part and drops into the opening without site cutting or silicone filler. Suitable for residential bay windows, oriel windows, and any angled window arrangement. Standard 2mm aluminium thickness. Maximum bay span depends on the angle and segment count, contact sales for spans over 4m total developed length. Bay cills carry a 10 to 14 day lead time on complex multi angle pieces, versus 3 to 5 days for standard profiles.
EWI Deep Projection Cill Profile
The EWI cill is purpose designed for external wall insulation retrofits. It covers the full depth of the insulation board (commonly 100, 120, 150, or 200mm) plus a 25 to 50mm overhang to throw water clear of the render face. Total projection commonly ranges from 150mm to 250mm. The cill includes a 30 to 60mm rear upstand that sits behind the window frame, a sloped top surface for drainage, and a 5mm drip lip on the underside of the front edge. SEAI compliant when specified correctly. The CILLS app calculates the required projection from your insulation depth automatically, so the cill cannot be ordered short. This eliminates the most common cause of failed SEAI thermal imaging inspections. Standard 2mm aluminium thickness. Marine grade 3000 series aluminium for coastal projects.
Commercial & Large Span Cill Profile
Commercial cills use 3mm aluminium thickness for spans over 2,000mm and projections over 200mm. Specified for apartment blocks, office buildings, schools, healthcare facilities, and any project where deflection under wind load matters. Available with stiffening ribs, integrated drip details, and concealed welded joints to maintain a continuous appearance across long elevations. Typical commercial cill spans range from 2m to 6m, with longer spans available as multi piece welded assemblies. Powder coated to architectural specification, commonly RAL 7016 anthracite grey or RAL 9005 jet black.
Custom & Bespoke Profiles
If our standard profiles do not match your specification, we design custom profiles to your exact drawing. Common bespoke requests include curved cills for circular windows, stepped profiles for stone reveals, integrated planter boxes, and architectural detail cills with custom drip arrangements. Lead time for custom profiles is typically 7 to 10 working days from drawing approval. Send drawings to info@cills.ie or call sales on +353 1 223 8774 to discuss bespoke requirements.
| Profile |
Thickness |
Max Length |
Projection |
Upstand |
Best For |
| Standard | 1.5 to 2.5mm | 2,000mm | 50 to 100mm | 20 to 40mm | New builds, standard openings |
| Bay | 2mm | Custom | Custom angle | 30 to 50mm | Bay windows, angles |
| EWI | 2mm | 2,000mm | 150 to 250mm | 30 to 60mm | Retrofit, external insulation |
| Commercial | 3mm | 6,000mm | Variable | Custom | Apartment, offices, schools |
