You might think that rust is not an issue for your home since you don’t have any exposed metal, but that is not true. Even if you don’t have a metal roof or metal siding, there are thousands of nails and screws throughout your home, as well as, metal rebar inside of the cement in your foundation. Rust is created when metal is exposed to air and water through a process called oxidation. Rust turns the metal porous and weak, and it also causes it to expand. If this happens to the rebar in the cement of your foundation, it is a very serious problem since the rebar will expand, causing the cement to crack and cause structural damage. It should be dealt with as soon as possible.
If you have nails on your roof that start rusting, you might see brown streaks down the side of your roof. While not an immediate problem, you should replace the nails as soon as possible since they won’t serve their purpose once they deteriorate further.