It's a cruel fact: Those factors that make home exterior siding so crucial are the same ones that undermine its performance over the long term. In other words, in defending your home against the hot sun, bitter cold, harsh wind, and precipitation, exterior siding protects your home from the elements, keeping your family comfortable and safe," . If your siding has begun to rot or crumble, then it cannot perform its vital role. In cases of circumscribed damage, you may be able to repair only the affected area. But if the rot has spread across the exterior, there's nothing to do but start over, this time with a rot-resistant mater.