This info is supplied by Bill Squiteri of A-Stat Home Inspection
most basic description for a roof is that it functions as an umbrella
for the home. Most roofs are not and can not be water or weather tight.
They are designed to simply shed water off of the roof and away from the
home. Flashing is the component that helps to bring a roof to its
closest weather tight state. Roofing systems are not intended to provide
insulation for a home (Flat roof vs. Pitched roof) nor does the roof
covering itself have a structural role, although most roofs are
installed over sheathing and the sheathing itself becomes a structural
component once it is attached to the rafters or pre-engineered trusses.
The most common defect that you will come across is missing shingles or a
hole in a roof from a falling branch or object from the sky. Most, if
not all roofing systems require repairs before they ever need to be
replaced. Replacing a system has more to do with water damage to the
deck sheathing or the age of the roofing shingles themselves. A new roof
with water leaking into the home is most likely the result of a
flashing defect and not a result of defective roof shingles. Let's look
at some common shingles that are used in the marketplace today:
Types of Shingles Found Today
- These are the most common types of shingles that you will see on
homes today. Fiberglass makes up the base material (organic felt is also
used in a small percentage of shingles) with asphalt for the body or
coating. Asphalt shingles were first manufactured in 1901 and have been
commonly used since 1911. The life expectancy of this style shingle is
12-25 years (depending on the quality and thickness of the shingle).
Slate is a natural stone roofing product. It can be thought of as
metamorphosed shale. The main constituents are mica and quartz, but
there are typically many other minerals in slate. Slate is quarried in
many areasÂ of the world (France, Spain, Wales, India,
China, Canada and right here in this great nation, the U.S.A.) Slate can
be extremely durable and is expensive to install. It has a life-span
from 35-75 years with some roofs in Europe being known to have lasted
over 1,000 years.
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Wood Shingles or Shakes
- Wood roofs were the most common shedding roof system used prior to
the advent of asphalt shingles. In some areas of North America, wood
shingles are still among the most common roofing materials. Several
types of wood have been used over the years with White Cyprus being the
best and Red Cedar being next. Some are now available pressure-treated
with preservatives. Wood shingles are typically sawn smooth and wood
shakes are typically rougher in texture and thicker. Shakes may be
split, sawn or both.
- Clay tiles have been used since the days of the Greek and Roman
empires in Europe, China and the Middle East. Clay roofing tiles are
expensive and labor intensive to install. They have an indefinite life
expectancy. Clay tiles are like slate in that the fasteners and
flashings are more likely to fail than the tiles themselves. Clay tiles
are made with fine clays shaped in molds while wet, and then kiln baked.
Temperatures of roughly 2,000Â°F bring the clay to a point of
vitrification. This means the chemicals in the clay, such as silicas and
aluminums, lose their individual identity and fuse together to form a
dense, glass-like nonporous structure. The density of these tiles
indicates the quality and is determined by the fineness and purity of
the clay as well as the duration and temperature of the firing process.