The junction problem: where roofs actually leak
The field of a roof, the open plane everyone looks at, almost never starts the leak. Water gets in where the roof meets something else, and this arc’s housing has junctions everywhere: additions at their own pitch, porch roofs, two-storey walls over garage roofs, and valleys carrying every afternoon’s rain.
- 1 Ridge and exhaust — Where the attic is supposed to breathe out. Sized in 1975 on half this arc.
- 2 The shingle field — The part everyone looks at. The sun works it from above, the attic from below.
- 3 The valley — Every afternoon’s rain, funnelled into one seam.
- 4 Wall flashing — Where the garage roof meets the house. Rebuilt metal outlives the shingles; caulk does not.
- 5 The vent boot — A rubber collar on a faster clock than the roof around it. The arc’s most common leak.
- 6 Eaves, drip edge and soffit intake — The hardware salt reaches first, and the intake the attic breathes through.
Why junctions fail first
A junction is where two systems have to agree, and the agreement is made of flashing: shaped metal, layered with the covering, directing water downhill past the joint. Done right it outlives the shingles. The problem is that on much of the older stock it was not done right the last time, it was caulked, and sealant in this sun is a consumable.
The lake-country cottages and bungalows compound it with geometry: additions built at odd pitches, porch roofs tied into main walls, and every one of those transitions is a detail someone had to get right decades ago and someone else has re-sealed since.
Reading a quote at the junctions
The single most revealing line in a replacement quote is what happens to the flashings: replaced, or reused and sealed? Reused flashing is the most common reason a new roof leaks in its first year, because the new covering is only as good as the oldest metal it drains onto.
On the newer two-storey stock, ask specifically about the wall-to-roof details: the garage roof meeting the main wall, and the step flashing run behind whatever cladding sits above it. Those junctions fail quietly, inside the wall, and they are exactly where a careful bidder earns the difference in price.