Roofing Materials and Maintenance

Roofing Materials

ASPHALT SHINGLE: Used on about 80% of all homes, the asphalt shingle is by far the most common type of roofing material found during a home inspection. These shingles are made of a layer of asphalt impregnated felt paper covered with an additional layer of asphalt. The granular material that gives a shingle its color is embedded into this top layer of asphalt. This type of roofing has a life expectancy of 15 to 20 years (less with multiple layers), and requires very little maintenance.

In the past asphalt shingles were classified by weight, the most common being 210 pounds per square. (The term “square” is the expression a roofer uses for the amount of material required to cover 100 square feet). They have an average life expectancy of 15 to 20 years. Heavier shingles such as 225s, 235s, and 320s, have life expectancies of up to 30 years.

Today, shingles are now classified by the manufacturer’s warranty.

They would now be known as 10 year, 15 year, 20 year, 25 year, and 30 year shingles. The reason for this change was the use of lighter fiberglass matting.

ASPHALT ROLLED ROOFING: Asphalt rolled roofing is made of the same material as asphalt shingles. It typically comes in rolls that are 18 or 36 inches wide.

Rolled roofing is usually installed on sloped or flat roofs. It can also be found in roof valleys. The material is considered to be of low quality with a life expectancy of 5 to 15 years. Warping and buckling due to expansion of the material is a common problem. The granular coating tends to break down quickly in the wrinkled areas resulting is localized wear and deterioration.

  • Periodically inspect rolled roofing for granular deterioration.
  • If installed in roof valleys, check for cracking, tearing, and deterioration.
  • Be sure all overlaps, edges, and surface nails stay well sealed.

SINGLE PLY MEMBRANE:Single ply membrane roofing is usually modified bitumen asphalt, plastic, or rubber. The roofing can be torched, tarred, glued, or mechanically fastened with strips or buttons. The life expectancy of this material has not yet been time tested. It has been installed in the U.S. since the early eighties. Some manufacturers provide a ten year warranty and claim thirty year life expectancies.

Most of the problems associated with this material has been with installation and not the products themselves.

WOOD SHINGLES & SHAKES: A wood shingle is cut with a machine, whereas a wood shake is hand split or mechanically split. A wood shake is much thicker than a wood shingle and has an uneven surface. The two most common woods used for making shingles are cedar and redwood.

The life expectancy of a wood shingle (or shake) is thirty to forty years. Many factors affect the life span of the material such as exposure (the amount of shingle exposed to the weather), the quality of the wood, the pitch of the roof,and exposure to the sun and shade. Too much sun will cause the shingle to become brittle and crack. Too much shade will promote moisture and rot.

TAR & GRAVEL: Tar and gravel, or built-up roofs are designed for flat roof applications. They consist of two to five layers of roofing felts with a mopping of asphalt between layers. A coat of asphalt is then applied to the top and embedded with gravel. The gravel is intended to reflect the sun’s damaging rays and protect the roof from mechanical damage.

Two ply roofs have a life expectancy of 5 to 10 years while four ply roofs typically last 15 to 20 years.

SLATE: Slate roofing installed after the 1940’s is rare. The life expectancy of a high quality slate roof is 60 to 200 years. The most common problem with this type of roof is not the slates themselves, but the nails securing the slates.

Eventually the nails will rust and allow the tiles to slide out of place. There are several types of brick, the two most common being clay and cement. The characteristics of each varies dramatically. Some have very soft, porous surfaces while others are extremely hard.

Routine Maintenance:

Spring and Fall are typically the best times to perform the routine maintenance required for your roof.

  • Check for loose, damaged, or missing shingles.
  • On flat roofs, check for cracking and blistering.
  • Inspect flashings around chimneys, skylights, plumbing stacks, etc.
  • Check vents, louvers, and chimneys for bird or insect nests.
  • Keep all debris cleared from roof, especially in the valleys.
  • Check facia and soffit boards for water penetration or decay.
  • Trim back tree limbs growing over roof.

The Most Common Causes of Roof Leaks:

  • Improper flashing around chimneys, plumbing stacks, skylights, etc.
  • Missing or broken shingles.
  • Tears in roof valleys.
  • Ice damming due to improper run-off, forcing water back up under the shingles.
  • Improperly hung gutters or drip edge.
  • Improperly installed or wrong type of roofing.
  • Cracking or deteriorated chimney caps.


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