Window Head Flashing Detail
The window head flashing is a horizontal aluminium piece installed above the window opening, projecting 50 to 80mm out from the wall face. It throws water clear of the window frame and prevents water tracking down the wall and entering the window head. Standard detail includes a rear upstand of 30 to 50mm tucked behind the render or cladding, a 5 degree top slope toward the front, and a 5mm drip lip on the underside. On EWI retrofits the head flashing must project past the full insulation depth plus a 25mm minimum overhang. Head flashings are commonly powder coated to match the window frame or render colour.
Window Sill Flashing Detail
The sill flashing sits under the window opening and serves a similar function to the cill on the exterior. On many EWI retrofits, the sill flashing and the cill are a single combined piece. On other details, the sill flashing is a separate weatherproofing layer installed behind the visible cill. Either way, the detail must include a continuous turn up at the rear (behind the window frame), a sloped top surface, and a drip lip at the front. Failure of the sill flashing is the single most common cause of water ingress at window openings.
Parapet Wall Flashing (Coping)
Parapet flashing, often called coping, sits on top of a parapet wall and weatherproofs the upper edge of the wall. The detail must cover the full wall thickness plus a 25 to 50mm overhang on each side, with drip lips on both undersides. The parapet flashing is typically a folded U section in 2mm aluminium, fixed with concealed brackets to allow thermal movement. Joints between sections are typically lapped 100mm with a continuous mastic seal. We weld parapet flashings up to 6m in single pieces to minimise joints on architectural projects.
Abutment Flashing Detail
Abutment flashings weatherproof the junction where a roof meets a vertical wall, common at chimneys, dormers, and lean to extensions. The detail consists of a stepped or continuous aluminium upstand fixed to the wall and dressed onto the roof covering. Standard upstand height is 150mm minimum to comply with Irish Building Regulations. The flashing is fixed with concealed brackets or chase fixed into a horizontal mortar joint, with a continuous mastic seal at the top edge.
EWI Specific Flashing Junctions
External wall insulation creates new flashing requirements that did not exist on traditional construction. The insulation board terminates at every opening, every parapet, every roof junction, and every change in plane. Each termination needs a flashing detail that protects the insulation edge from water ingress. Common EWI flashings include the v shaped upstand flashing at the wall plate, the L shaped insulation start flashing at the base of the wall, the cap flashing over insulation terminations, and the corner flashing at internal and external corners. We fabricate every standard EWI flashing profile, plus custom profiles to architect drawings.
