Metal & Crittall-Style Restoration Windows
The slender sightlines of 1920s Art Deco and 1930s modernist steel fenestration require the slimmest possible perimeter seals and exact rebate calculation.
The Challenge of Shallow Steel Rebates
Traditional hot-rolled steel sections (such as SMW or W20 profiles) feature exceptionally compact rebate dimensions, often only 6mm to 8mm deep.
Standard sealed units with 10mm or 12mm sightlines will expose the shiny metallic spacer bar and black secondary sealant well above the steel frame sightline, destroying the crisp geometric aesthetic.
By specifying a 5.5mm sightline with a black warm-edge spacer bar and 4mm cavity (11mm overall thickness with 3mm float), the seal remains fully concealed within the steel frame rebate.
Ensure existing steel frames have been fully cleaned of corrosion, treated with zinc-phosphate rust-inhibiting primers, and checked for frame squareness prior to measuring.
Configure Metal Frame Units
5.5mm slim sightline units tailored to shallow steel window frames.