You notice it on a morning walk around the enclosure: fine black speckling across the mesh, worse near the corners and along the shaded side, the kind of dirt that doesn't wipe off with a dry hand.

A screen door earns its keep for years before anyone thinks much about it. Then one afternoon it won't quite latch, or it drags across the track instead of gliding, and suddenly you're standing there wondering if a quick fix will hold or if the whole thing needs to come out.

By mid-afternoon, one side of a screened pool deck can feel noticeably hotter than the other, even though both sides sit under the same aluminum roof.

A screen panel that bows out of its frame, or drops free entirely, is one of the most common calls on a pool enclosure. It looks alarming, and it does invite trouble, but the cause is almost always small and specific.

If your enclosure has a dog that leans on the lower panels or a cat that treats the mesh like a climbing wall, you already know how fast standard screen gives out.

A screen enclosure looks like it should take care of itself. The mesh sheds rain, the aluminum does not rust like steel, and the whole thing just sits there over the pool or patio.

Aluminum does not rot, and it is not a food source. So the first thing worth clearing up is that the mold on your enclosure is not living on the metal itself. It is living on everything that lands on the metal.

Rust is specifically iron oxide. It only forms on metals that contain iron, which means steel and cast iron. Aluminum contains no iron, so it cannot produce rust at all.