Standing seam metal roof

A covering of metal sheet (zinc-titanium, copper, steel, aluminium) made of strips joined by raised vertical seams. The joint, lifted above the water plane, is watertight even at low pitch; hidden clips let the expanding metal slide. Light, extremely durable and with a clean line.

The standing seam roof solves the tightness of a metal roof with the geometry of the joint, not with sealants. The metal strips, as long as the slope, are joined along their edges with a raised double fold - the standing seam - that takes the joint well above the water plane. The fixing is hidden: clips hooked onto the fold hold the covering without piercing it.

On a metal covering the water runs in the channels between one fold and the next; the weak point is the joint. By lifting it with a double seam of 25 mm and more, the joint stays above the level the water reaches even in driving rain and wind: the roof becomes watertight at far lower pitches than a discontinuous covering (down to 5-7%). No through-fixing pierces the covering in the field: tightness does not depend on gaskets that age.

Metal expands greatly with heat: a long strip, warmed by the sun, lengthens by millimetres for every metre. If fixed rigidly, it would buckle or tear. For this reason the fixing clips are partly sliding (fixed clips and sliding clips): they hold the covering against the wind but let it move freely. The length of the slopes and the clip spacing are sized on the expansion coefficient of the chosen metal.

A metal covering has two weaknesses to manage. Condensation: the metal, cold and impervious, can cause the vapour arriving from inside to condense on its back; for this it is laid on a continuous support with a separating drainage layer and, above all, on a well-ventilated build-up with correct vapour control. Noise: rain and hail on metal are loud, and are attenuated by the solid support (boarding) and by the mass and insulation of the build-up below.