Premature rusting problem with a zincalume box gutter in Sydney inner west

lead flashing causing cathodic reaction on zincalume surface

Sydney’s inner west have tighter building areas and inner west roofs tend to have an extreme mixture of elements that can cause roof leakage problems that require major roofing repairs.

While box gutters are mainly used in the domain of commercial roofs, they are sometimes used on residential roofs. And because roofs in Sydney’s inner west demand a bit of innovation where there are space restrictions and architectural flair, box gutters are sometimes used. It is also an area in Sydney where the nice looking Velux skylights are often installed.

While a well designed box gutter will perform quite well, sometimes they are not put together correctly. And sometimes even if the installation is carried out corrrectly, someone does something afterwards that is somewhat troublesome.

Like this electrolysis problem with lead flashings from Velux skylights that I saw on a roof in Sydney’s inner west that will require a box gutter replacement…

The flashings used by the Velux skylight manufacturers are lead based. The Velux skylights are often installed on zincalume and colorbond metal roofs. Colorbond tends to have a much higher resistance to the ‘galvanic’ corrosion between the dissimilar metals. Zincalume on the other hand will corrode quite rapidly when damp conditions exist for long periods between the two metals.

So, it is very common on zincalume metal roofs to find rust problems when there is a Velux skylight involved.

… Hope you enjoy the video below: