Gable Flashing by Height

Gable Wall Flashing (Rufo) Quantity Calculator

A rufo de empena (gable wall flashing) is a strip of metal or PVC that sits in the joint where the roof slope meets the gable wall, keeping water from working its way in. How much you need comes down to the perimeter of that roof-and-wall interface. When the gable is an isosceles triangle you can work it out with L = 2 · √(horizontal² + height²), where horizontal is the wall width and height is how far the apex rises above the eave.

You'll usually see three materials: galvanized steel, which is the cheapest; aluminum, which shrugs off corrosion; and copper, which costs more but lasts a long time. Brazilian standard ABNT NBR 6125 asks for a flange of at least 10 cm per side, one leg against the wall and the other over the tile, sealed with MS Polymer (Soudal Fix All, Sika Multiseal) so the joint stays watertight.

Applications

It shows up on homes, shops and industrial roofs alike, anywhere a sloped roof butts against a vertical wall: gable ends, dormers, chimneys, parapet transitions. Get the rufo right and you remove the leak that plagues pitched roofs more than any other, while sparing the masonry from soaking up water, blooming with efflorescence, or taking structural damage over the years.

FAQ

How much flashing do I order with 10% waste? Take the calculated length and multiply by 1.10. That covers the overlaps (at least 5 cm between pieces) and whatever you lose to cutting. Stock pieces run 2 or 3 m long.

Galvanized or aluminum? Aluminum goes 25+ years without corroding, which is why it wins out near the coast. Galvanized steel costs less, but plan on repainting it every 5–7 years if the air is salty or damp.

Do I still need sealant if the flange is 10 cm? Yes. Run a continuous bead of MS Polymer along the top flange where it meets the wall. In a driving rain, capillary action will otherwise pull water behind the flashing, and that bead is what stops it.