Discoloration of Siding and Other Outdoor Surfaces

Hello, and welcome back to the CTHIS blog. I'll bet that you have walked around your house recently and discovered that the siding has some odd discoloration in localized areas. Or maybe you noticed it on a deck or patio area. Maybe you've looked up on the roof and seen something growing up there. Well, that discoloration is one of a number of different things, algae, moss, possibly mildew or mold or even rust.

ALGAE

A lot of houses develop algae problems throughout their life. Most of the time its not a problem. But if left untreated, algae can certainly become a nightmare to deal with. Algae typically grows on the northern side of a house where there is plenty of tree coverage. This is because algae enjoys moisture and an area that receives less sunlight will be moist for longer periods of the day. Having algae growing on the side of a house can get pretty ugly but a simple power wash will usually do the trick.

The real problems start when it grows on the roof, especially a shingled roof. Shingles are specifically designed to be heavy, durable, and reflective, and algae growth undermines all three of those elements. Most shingles contain limestone. Algae eats limestone. This leads to a breakdown of the shingle reducing its weight and in turn its durability. Algae also produce a special pigment that helps absorb sunlight causing shingles to reflect less light and thus heat the roof more rapidly and cool more slowly.

MOSS

Roof moss is similar to algae insofar as where and how it grows. People tend to think that roof moss is somewhat more aesthetically pleasing, it has a certain forest-fantasy-wonderland appeal to it. However, moss is insatiable and it will stop at nothing to conquer every inch of space on a roof no matter the material - wood, metal, clay, concrete, even asphalt shingles - as it grows it will actually lift and move roof covering materials like shingles or tiles out of place, giving water access to the roof deck. Moss is usually taken care of through a combination of mechanical and chemical removal processes and most home washing businesses offer roof cleaning services. Preventative measures include trimming back trees and installing zinc or copper strips along the ridge of the roof.

MILDEW

Mildew and mold are both big issues, especially here in the down east. They both carry major health concerns and with our weather both are ever-present threats to our homes. Mildew is often grey and powdery and mold typically manifests as black spotting. Both can be found on shady areas of a home's siding. While mildew and/or mold on the outside of your house isn't necessarily a big deal - unless you spend a lot of time in that particular area of your property - those exterior fungi may release spores that soon find their way inside. Long-term exposure to either can have deadly consequences so catching them early and taking care of them quickly is the best course of action.

RUST

Rust is the oxidation and deterioration of metal, and when you see bright orange streaks down the side of your house its a sign that big things are happening. The good thing about rust stains is that they will lead you back to the source, the bad thing is that the metal that is deteriorating will need to be replaced and measures will need to be taken to prevent water from reaching that area again. Rust stains appearing are can be a sign that something wasn't done quite right in the area - flashing was improperly installed, or caulking is missing, or siding channels were incorrectly lined up - but it could be somewhat less drastic. In the image below the likely cause of this stain is a rusted air handler condensation catch pan that has begun to drain out. The catch pan will need to be replaced and a qualified technician should be brought in to diagnose why the air handler is leaking.

So, the next time you see discoloration on your home think about the different reasons for why those stains have appeared and remember to take action sooner than later to remedy the underlying issues.

Thanks for stopping in, and as always, if you're in the market for a home inspector in North Carolina, go ahead and use my online scheduler to book your next home inspection!

Until we meet in person,

Zac