Where Shingle Roofs Leak: It Is Almost Never The Field

The chimney

Three separate details, any of which can leak. The crown - the concrete slab on top - cracks with heat and age and lets water into the masonry itself. The flashing where the shingles meet the brick, which relies on a step-and-counter arrangement that is easy to get wrong and easier to caulk badly. And the cricket on the uphill side, which diverts water and debris around the chimney - if it exists, is big enough, and is not full of leaves.

Pipe boots

Every plumbing vent through the roof is sealed with a rubber collar on a metal or plastic base. Rubber and Florida sun do not get on. The collar cracks, usually at the top where it grips the pipe, and water runs down the outside of the pipe into the attic. It is the single most common shingle-roof leak we see, it is a quick replacement, and it is completely invisible from the ground.

Wall and step flashing

Where a roof slope runs into a vertical wall, each course of shingle gets its own piece of step flashing, tucked under the siding or stucco above. Where the slope ends at a wall, a headwall flashing does the same job across the top. Both fail through corrosion, through stucco applied straight over them, or through a previous repair that replaced flashing with sealant. Sealant is not flashing. It is a promise that lasts about a year.

Valleys

Two slopes' worth of water in one channel. On shingle, valleys are either open (a metal channel between the shingle edges) or closed (shingle woven or cut across). Either way, the valley is where water runs fastest and debris collects, and it wears before the field does.

Skylights and vents

Every hole in the roof is a flashing problem someone had to solve. Skylight curbs, attic vents, satellite mounts, solar standoffs - each one was sealed by whoever put it there, with whatever they had. A roof with many penetrations has many small chances to leak.

The pattern

None of these are visible from the driveway. All of them are visible from the roof. That is the whole case for someone looking every year: the field will tell you it is ageing from the street, but the details - which are where the water actually comes in - will not.

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