Drainage
Downspouts & foundation
Roof water at the footing is a common cause of damp basements and crawls — often fixed with extensions and grade.
A downspout that ends at the footing concentrates roof water exactly where you do not want it. Over a wet season that shows up as damp crawl soil, musty air, or basement staining.
Extensions that move water several metres away are one of the highest-return homeowner moves. They need to stay put in wind and not crush flat.
Check grade next: soil should fall away from the foundation, not toward it. Mulch volcanoes and settled beds reverse that slope over time.
If indoor damp continues after roof water is controlled, look under the house and at wall condensation before assuming a full waterproofing system is required.
Educational only — not a contractor inspection or bid. When work is structural, electrical, or involves unknown vent chases, hire a qualified local trade.