Why are rust marks appearing on my guttering?

Marks on the wall? On the gutter itself? Coming down the downpipe?

Rust. A reddish- or yellowish-brown flaking coating of iron oxide that is formed on iron or steel by oxidation, especially in the presence of moisture. Some use rust to create a desired image or finish. However, in most cases (and certainly this one) it is most unwelcome. In this short article we try to understand why this may occur, and what you can do to prevent such a thing happening.

First things first, plastic doesnt rust (obviously) so this is more focused on steel guttering. In our case, we will refer to Lindab guttering as that is the range that we are currently supplying. Lindab supply a galvanised finish, and also a powder coated finish, the latter having a longer warranty than the first. If the guttering is around 15 years old, then rust patches will be expected on the inside of the gutter, especially if the system hasnt been maintained and cleaned every six months.

The number one problem that causes rust spots, is the use of a zinc or galvanised coated fixing. We recommend using stainless steel fixings ONLY to stop this occuring. If the fixings used were not stainless steel, over a period of time a rust patch will appear on the wall below the fixing, leaving a dirty mark on the property.

Another cause for rust on these systems, (mainly galvanised) is the use of a power tool to cut the guttering/downpipe. An angle grinder or a holesaw will generate enough heat, that it breaks down the galvanisation and therefore your gutter will rust a lot quicker than expected. Lindab recommend only using hand tools such as a hacksaw for making your cuts.

The last cause that is the least common, but still happens, is when the powder coated guttering is assembled but the cuts havent been painted. Cutting through the powder coat, means that you need to paint over any exposed ends to protect the bare metal. Touch up paints are supplied in the respective colours and you can find them here. Its lazy not to apply this extra step, and actually it voids your warranty! Worth doing dont you think?