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Through-wall flashing, end dams and weeps · Lesson 2 of 4

Through-wall flashing, end dams and weeps: materials, standards and design constraints

Why BIA endorses stainless steel and copper and does not recommend galvanized steel or aluminum, how membranes use a metal drip edge, the weep and lap numbers and who publishes each, and what AFS can make.

You will be able to: Choose a through-wall flashing material from published guidance, state which numbers are recommendations, code limits or manufacturer values, and match them to what AFS can fabricate.

11 min · 11 slides · 8 questions

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Slide 1 of 11

Which metals BIA endorses

BIA calls stainless steel an excellent rigid flashing material, with superior chemical resistance, that does not stain masonry.

It calls copper another excellent rigid flashing material, durable and easy to form and solder, though exposed copper may stain adjacent masonry.

What BIA says about each flashing materialA table of six rows. Stainless steel and copper are marked as excellent rigid flashing. Galvanized steel is marked not recommended and aluminum as not for brick masonry. Polyethylene, felt and paper are not flashing materials. Flexible membranes that fade in sunlight need a metal drip edge. A column shows that AFS can fabricate the four metals.Metal or materialAFS makesStainless steelBIA: excellent, Type 304YesCopperBIA: excellent, may stainYesGalvanized steelBIA: not recommendedYesAluminumBIA: not in brick masonryYesPoly, felt, paperBIA: not flashing materialsn/aFlexible membraneBIA: sun needs a drip edgen/aSource: BIA Technical Note 7A. A metal AFS can makeis not a recommendation for through-wall use.

A table of six rows. Stainless steel and copper are marked as excellent rigid flashing. Galvanized steel is marked not recommended and aluminum as not for brick masonry. Polyethylene, felt and paper are not flashing materials. Flexible membranes that fade in sunlight need a metal drip edge. A column shows that AFS can fabricate the four metals.

BIA Technical Note 7A on each material. The AFS column says only what the shop can make; it is not a recommendation to use a metal in a wall.

Sources

Glossary

Type 304 stainless steel
The stainless grade BIA names for through-wall flashing, to ASTM A240/A240M. BIA calls stainless an excellent rigid flashing material that does not stain masonry.
Mill-galvanized steel
Galvanized steel whose coating is not hot-dipped, so the protective layer is thinner. BIA says bending cracks it, and does not recommend galvanized steel as through-wall flashing.
Drip edge
A sheet-metal edge, typically stainless steel, paired with a flashing membrane that fades in sunlight; it extends past the brick face so water leaves the wall while the membrane stays concealed.
Termination bar
A flat metal or plastic bar, about 1 in wide with predrilled holes, that clamps and fastens the top of flexible flashing to the backing, with sealant along its top edge.
Mortar collection device
A drainage material or insert in the air space that catches mortar droppings so they do not bridge the cavity or block the weeps. It does not replace careful bricklaying.