Underlayment, starter, flashing, fastening and roof geometry all affect how the finished roof handles water and wind.
How Shingles Shed Water
Shingles are installed in overlapping courses.
Rain runs from one course onto the next until it reaches the roof edge.
That simple principle becomes more complicated around:
- valleys;
- walls;
- plumbing vents;
- chimneys;
- dormers;
- changes in roof slope.
These areas require flashing and careful integration with the surrounding shingles.
Architectural Shingles
Architectural shingles use laminated construction to create a thicker, dimensional appearance than traditional three-tab styles.
Products vary by manufacturer in construction, wind ratings, impact options, warranty terms and color.
Shingle warranty terms and expected service life vary by product, installation and roof conditions. The specifications for the actual shingle being proposed are more useful than a single lifespan claim applied to every asphalt roof.
The installed product determines those details.
Underlayment
Underlayment sits between the deck and shingles.
It provides another layer within the roof assembly and helps protect the deck during and after installation.
The correct material and installation approach depend on the roofing system and project requirements.
It works with the shingles and flashing; it does not replace them.
Starter Material
The first course along roof edges needs a proper starting point.
Starter shingles or strips help secure the edge and establish the overlapping pattern for the courses above.
Roof edges receive significant wind exposure, so this part of the installation deserves the same attention as the more visible areas.
Shingle Fastening
Correct fastener placement is important.
Fasteners installed too high, too low or improperly driven can affect how the shingle remains attached.
Installation should follow the requirements of the selected product rather than a generic nail pattern applied to every roof.
Shingle Repair
Localized repairs are often possible when surrounding material remains serviceable.
Examples include:
- missing shingles;
- wind damage;
- small damaged sections;
- repairs around penetrations;
- localized flashing work.
Older shingles can become more difficult to work with as they age, so repairability depends partly on the material around the damaged area.
Shingle Replacement
Replacement becomes more practical when deterioration extends across large portions of the roof.
The project should address deck condition, underlayment, starter, flashing and ridge components as well as the visible shingles.