Valleys & Flashings
Valleys and flashings that are rusting are recommended to be sealed with an anti rusting agent.
Stone Roofs - Coverings
This type of covering on a pitched roof requires ongoing annual maintenance. We recommend that a roofing contractor evaluate this type of roof. Infra-red photography is best used to determine areas of potential leaks.
Flat Roofs
Flat roofs are very vulnerable to leaking. It is very important to maintain proper drainage to prevent ponding of water. We recommend that a roofing contractor evaluate this type of roof.

ROOF TYPE LIFE EXPECTANCY SPECIAL REMARKS
Asphalt
Shingles 15-20 years Used on nearly 80% of all residential roofs; requires little maintenance
Asphalt
Multi-Thickness Shingles* 20-30 years Heavier and more durable than regular asphalt shingles
Asphalt
Interlocking Shingles* 15-25 years Especially good in high-wind areas
Asphalt Rolls 10 years Used on low slope roofs
Built-up
Roofing 10-20 years Used on low slope roofs; 2 to 3 times as costly as asphalt shingles
Wood Shingles* 10-40 years1 Treat with preservative every 5 years to prevent decay
Clay Tiles*
Cement Tiles* 20 + years
20 + years Durable, fireproof, but not watertight, requiring a good subsurface base
Slate Shingles* 30-100 years Extremely durable, but brittle and expensive
Asbestos
Cement Shingles* 30-75 years Durable, but brittle and difficult to repair
Metal
Roofing 15-40 + years Comes in sheets & shingles; should be well grounded for protection from lightning; certain metals must be painted
Single Ply
Membrane 15-25 years
(mfgr’s claim) New material; not yet passed test of time

* Not recommended for use on low slope roof 1 Depending on local conditions and proper installation
2 Depending on quality of slate

Roof covering should be visually checked in spring and fall for any visible missing shingles, damaged coverings or other defects. Before re-roofing, the underside of the roof structure and roof sheathing should be inspected to determine that the roof structure can support the additional weight of the shingles.

Wood shakes and shingles will vary in aging, due to quality of the material, installation, maintenance, and surrounding shade trees. Ventilation and drying of the wood material is critical in extending the life expectancy of the wood. Commercial preservatives are available on the market, which could be applied to wood to impede deterioration.