What happens if I use galvanized straps on a copper downspout?

The galvanized steel rusts within a few years, producing rust staining on the wall directly below each strap. The strap itself eventually fails. Bronze straps cost marginally more and last the life of the system without rusting or staining.

How many downspout straps do I need?

One strap every 5 to 6 feet of vertical run, plus one strap within 12 inches of the top and bottom of each downspout section. A 10-foot section of downspout needs a minimum of three straps.

Can I use copper wire to strap a downspout instead of a formed strap?

Historically, copper wire wrapped around the downspout and driven into a masonry joint was used for this purpose. It is acceptable on masonry buildings where driving wire into mortar joints is practical. A formed strap is the more reliable and more finished-looking solution on wood-framed buildings.

Bronze Downspout Straps — Old Canaan Building Materials

The downspout strap is one of the most visible pieces of hardware on a traditional copper gutter system, and it is almost always wrong. The round copper downspout needs to be held to the wall at regular intervals, and the strap that holds it should be in the same material family as the downspout — copper or bronze — not galvanized steel painted brown, which is what most installations use.

The Character

A bronze downspout strap is a simple thing: a bent strip of bronze or copper, 3/4" to 1" wide, that wraps around the downspout and fastens to the wall with a single screw through a mounting plate. At 5 to 6 foot intervals down a 3" or 4" round downspout, the straps read as a rhythm of small details against the wall. In bronze they develop the same dark patina as the downspout. In galvanized steel they rust.

What It Is

Downspout straps for copper or bronze gutter systems should be copper or silicon bronze. Standard strap dimensions: 3/4" to 1" wide, 0.050" to 0.064" gauge copper, with a formed mounting plate and a single stainless steel or bronze screw. They are available from copper gutter supply houses and specialty hardware dealers.

How It Behaves

Bronze and copper downspout straps are essentially permanent. They do not rust, do not need painting, and develop the same patina as the downspout they secure. The mounting screw is the only potential failure point — use a stainless steel or bronze screw, not a galvanized one, which will rust and stain the wall below.

Why It's Right

Every visible piece of hardware on a copper gutter system should be in the same material family. Galvanized steel straps on a copper downspout produce rust staining on the wall within a few years. The cost difference between galvanized and bronze straps is negligible against the cost of the copper system. Specify bronze.

How To Get It

From copper gutter supply houses and specialty hardware dealers. Specify "copper or silicon bronze downspout straps" to the sheet metal contractor installing the gutter system. This is a simple substitution that the contractor should make without question.

The Old Canaan Standard

Silicon bronze or copper downspout straps, 3/4 to 1 inch wide, at 5 to 6 foot intervals, with stainless steel or bronze mounting screws, for all copper downspout installations on traditional New England buildings. No galvanized steel straps. The hardware is visible and it should be in the same material family as the system it secures.

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Bronze Downspout Straps

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