Use this atlas page to organize evidence, not to declare a diagnosis. Snow cover, ice and heat loss alter drainage and attic temperature patterns. The useful starting point is a repeatable pattern tied to location, timing and conditions that changed or stayed normal.
Read the visible pattern
Treat snow load and freeze-thaw as a controlled observation window rather than background context. Record the first location, direction, edge or cycle where the symptom becomes noticeable. Photograph from the same position, preserve original timestamps and note comparable areas that remain dry, quiet, cool or odor-free.
Trace the connected mechanism
Water can travel laterally along membranes, decking and framing before becoming visible far from the entry point. Compare at least two plausible routes rather than choosing the first familiar explanation. Compare the roof drainage pathway with other sources that could create the same visible symptom. A strong hypothesis predicts where the symptom should begin, what trigger should reproduce it and which nearby areas should remain unaffected.
Use safe, non-destructive checks
- Record the start and end of snow load and freeze-thaw
- Compare the first affected point in the attic
- Record rain intensity and wind direction
Pair every reading with its instrument, location, time and environmental condition. One reading can support a pattern but cannot certify a hidden material condition or prove that a repair is complete.
Respect the stop boundary
Do not walk unsupported framing, disturb suspect insulation or approach damaged wiring. Active roof leakage, sagging materials or widespread decay needs qualified assessment.
Prepare the next decision
Summarize the trigger, first visible change, rooms or systems involved, checks already completed and what would count as a verified outcome. A useful handoff gives the next person a timeline and competing explanations instead of only a symptom label.
Primary references for this topic family
These references ground the general building-science or safety context. They do not diagnose a specific house, replace local requirements or certify a repair.
