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 bitumen 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
We accept payments by check, Visa, and
MasterCard 