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Installing parapet wall coping correctly is one of the most critical stages in weathering a home extension. A poorly installed capping can lead to structural water leaks, damage to external wall insulation (EWI), and masonry degradation. This guide provides a detailed, step-by-step procedure for installing modern, secret-fix aluminium parapet cappings on Irish extensions, ensuring compliance with local Building Regulations and a 100% watertight finish.
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The top surface of the soleplate must slope at a minimum gradient of 1:40 (approx. 1.5 to 2 degrees) angled inward towards the roof drainage system to prevent dirty rainwater from staining the building's front facade.
Position aluminium mounting brackets at 1-metre centres along the straight runs. Ensure brackets sit 50mm away from joint zones and secure them with high-grade stainless steel anchors.
Bring the roof membrane up the vertical face of the parapet (minimum 150mm upstand) and fold it flat across the soleplate, anchoring it down before installing capping.
Always fit corner units and stop ends first to establish correct lines. Use factory-welded joints from cills.ie to guarantee structural watertightness at vulnerable angles.
Hook the outer drip-nose edge over the bracket hooks, then press down to click the inner edge in place. Always leave a 3mm to 4mm expansion gap between sections.
Apply neutral-cure silicone beads to the internal jointing plates, slide them beneath the capping gaps, and snap adjacent lengths together for a robust, weather-tight joint.
Yes, but we highly recommend installing an 18mm plywood soleplate or treated timber bed first. It makes levelling easier, allows you to create the required fall easily, and provides a much more secure fixing base for the brackets.
Always use high-grade stainless steel fixings. Standard steel screws will rust rapidly in the damp Irish climate, causing structural failure and staining the brickwork or render.
Use a sliding mitre saw fitted with a sharp, high-tpi non-ferrous metal cutting blade. Work slowly, support the capping on foam pads, and wear safety glasses. Deburr the cut edge with a fine metal file.
For walls that are not at 90 degrees, measure the angle using a digital protractor and submit it to cills.ie. We will factory-weld a custom angle corner piece in our workshop to fit your wall perfectly.
Use a premium, low-modulus neutral-cure silicone sealant. Do not use standard acid-cure (acetoxy) silicones, as they can react with the aluminium and fail to adhere to the powder coating.
For short runs and narrow widths, one person can manage the installation. However, for 3-metre lengths and corners, we recommend a two-person team to ensure alignment and prevent scratching the powder-coated finish.
No. The brackets are engineered with a friction hook system that holds the capping under tension. For high-exposure coastal sites, we can provide heavy-duty spring clips that provide additional resistance against wind vibration.
A typical 20-linear-metre flat-roof extension parapet can be fully prepped, bracketed, and capped by two experienced installers in 4 to 6 hours.
Powder coating protects the metal, but raw cut ends are highly corrosion-resistant on their own. However, for marine or coastal applications within 1km of the sea, we recommend applying a thin coat of matching RAL touch-up paint to any cut edges.
When you order your capping system from cills.ie, all necessary brackets, joint plates, and installation guides are calculated automatically and included in your package.
Get connected with vetted local capping contractors for a professional installation.