Roofing, Flashings and
Chimneys
The primary function of the roof
system is to protect against and
manage the weather elements,
particularly precipitation, thereby
protecting the interior and
structural components of the home.
For the purposes of a home
inspection, the roof system consists
primarily of the roof coverings,
flashings and chimney.
In addition to protecting the
interior elements of the home the
roof components should also be
designed, in conjunction with the
gutters and downspouts, to direct
rainwater and runoff away from the
foundation area, to help reduce the
potential for soil erosion,
compaction and water entering the
basement area.
Because of the important functions
this system provides, it's condition
should be assessed regularly, and
maintenance provided when and
wherever necessary.
Roofing
There are two basic types of
roof
construction, sloped (also
called pitched) and flat. Most
sloped roofs are covered with
individual pieces of shingling
material overlapped to prevent water
penetration. flat roofs are
basically watertight membranes that
should have just enough slope to
allow water to run off. The slope of
a roof can be a factor in the life
expectancy of the roofing material.
The life expectancy of a roof
covering is also dependent upon the
type of material used, the quality
of workmanship, exposure to sun and
wear from tree branches, snow/ice
and wind. For example, south and
west roof faces have a higher wear
factor than north or east exposures,
highly reflective shingles tend to
have a longer life expectancy, and
cement or slate roofs last much
longer than standard asphalt
shingles (and cost a lot more!)
Asphalt shingling is the most common
roofing material used in residential
construction in Canada. Other types
of covering for sloped roofs include
asphalt roll roofing, concrete or
clay tiles, wood shakes and
shingles, and slate shingles. There
are also fiberglass shingles, metal
shingles and metal sheet roofing
systems.
Flat roofs are built up with layers
of molten asphalt and felts, or
covered with a membrane of modified
bitumin or asphalt base, or plastics
or rubber. Most are heat-sealed and
some are glued.
Flashings
The purpose of flashings is to
prevent the entry of water at areas
on a roof where two components join
together or intersect (i.e. one roof
to another or a chimney thru a
roof). Flashings can be constructed
of galvanized steel, tin, aluminum,
copper, lead or lengths of
roll-roofing. The choice of flashing
material will be dependent upon the
construction of the roof and the
material used for the roof covering.
Flashings will expand and contract,
metal in particular, with heat from
the sun and air temperature changes.
They are also expected to move and
stretch with typical building
shifts. The areas where flashings
are required are typically very
vulnerable to water penetration.
There is a high risk of water
leakage and wood decay from a
damaged, loose or poorly constructed
flashing. For all of the above
reasons, regular monitoring and
routine maintenance of the flashing
areas is essential to preventing
leaks.
Chimneys
The most common materials used in
chimney construction are masonry and
steel. Masonry chimneys can be
brick, block or stone and are
sometimes stuccoed or parged.
Chimneys often have more than one
flue. A flue is a separate and
distinct channel for the smoke on
the inside of the chimney. In most
cases, each appliance within the
house must have a separate flue. In
certain cases, two gas furnaces on
the same floor within a house can
share a common flue, as can a gas
furnace and a gas hot water heater
on the same level. Some wood
furnaces are designed to share a
flue with an oil furnace, if at the
same floor level.
Some flues are unlined in that there
is masonry exposed on the inside of
the flue. Unlined chimney flues are
most common in houses built before
the Second World War. These unlined
masonry flues have performed
reasonably well for fireplaces and
oil-fired furnaces, however most
have deteriorated beyond a safe
condition. Gas appliances require a
suitable liner.
Flue can be lined with clay tiles or
metal liner. For more information
about chimneys and chimney liners,
refer to the "Heating" section.
Copyright Gil
Strachan - All rights reserved.
Article Source:
http://EzineArticles.com/?expert=Gil_Strachan
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