Why do Cape Cod roofs leak at the dormers and the valleys?
Because the dormer and the valley are where the roof changes direction, and water collects and runs into the joints there. Those joints are the first to fail on an older roof.
A dormer is a small roof projection with its own cheek walls and its own covering, and it meets the main slope at a junction that must be sealed. The valley is the internal angle where two slopes meet, and it carries the water from both. Both points are exposed to the most water on the roof, and both depend on the flashing and the underlayment being sound.
On a roof that has been patched over the years, the junction is often a mix of old and new material. The new shingle sits beside an old one that has aged differently, and the seal between them is the weak point. The roofer checks each junction and renews the flashing and the underlayment as part of the repair.
How does the age of the roof change the repair?
Older roofs have aged decking and underlayment, and a repair that only changes the covering can leave the base beneath it weak. The repair is planned to include the base where it is needed.
A roof that is many decades old has decking that has been wet at some point, and the boards may have softened at the edges and at the eave. A new shingle nailed into soft wood will not hold, and the repair fails at the nail line. The roofer checks the decking before the covering is repaired, and replaces the soft boards in the area of the repair.
The underlayment is also tested. Older underlayment can be brittle and split, and the water can get under the new covering through the split. Where the underlayment has failed, it is renewed in the area of the repair.
What about the old patches on the same roof?
Patches that were added without the decking or the flashing being checked often fail at their edges. The repair removes the failed patches and replaces them with a sound section.
A patch that covers a leak can hide a larger problem beneath it. The shingles around it may have lost their seal, and the decking beneath may be soft. Removing a failed patch and replacing the section with sound material is more reliable than laying another patch over the top.
The roofer notes the patches on the note, so the homeowner can see where the roof has been repaired before. That history is useful for the next check and for any later insurance or sale question.
Why do Cape Cod attics show stains that the roof does not?
Because the water runs along the rafters and the decking before it shows, and the attic is where the route is clearest. The stain on the rafter often points to the leak.
Water that enters at a dormer runs along the underside of the decking and the rafters. A stain on a rafter several feet from the dormer is the end of that route, and it is not the opening itself. The roofer follows the stain back to its highest point, which is usually the opening.
The attic check is therefore part of every Cape Cod repair. It is quicker to find the route from inside than to search the roof, and it confirms the repair has reached the real source.
What should a Cape Cod homeowner check between repairs?
The dormer junctions, the valleys, the attic corners near the gable ends and the eave where the decking meets the wall. Those are the places where a second leak tends to start.
After each storm, look at the dormer junctions from the ground for lifted shingles and cracked sealant. Check the ceiling corners near the valleys for new stains, and check the attic on a dry day for damp wood or frost.
The note from the repair lists the parts that need watching, and the homeowner should keep the note with the roof's other records. A roof that is checked at those points is much less likely to leak without warning.
- Dormer junctions for lifted shingles and cracked sealant
- Valleys and the ceiling corners below them
- Attic corners near the gable ends
- The eave where the decking meets the wall
