Why roofs fail
Ultraviolet at altitude, and a freeze that arrives most nights of the winter. A roof here is worked from two directions at once.
- 1 Ridge caps. Worked loose by a temperature swing that happens every single day.
- 2 The field. High-altitude sun dries the covering out from above, faster than the calendar says.
- 3 Valleys. Where two slopes drain as one, and where meltwater runs longest.
- 4 Flashing. Chimney joints, and the line where the garage roof meets the house.
- 5 The vent boot. Rubber cracks early at this altitude, well before the shingles do.
- 6 Eaves. Ice builds at the edge wherever the attic is leaking heat into the roof.
The six
Thin air, and what it lets through
A mile-high sun that dries shingles out years ahead of their warranty, and a freeze-thaw cycle that works every fastener and sealant strip. Ice damming at the eaves each winter (an attic-heat problem, not a snow problem). And flashing that outlives its sealant at every chimney and vent. Not one of those needs weather worth remembering.