Roof Decks
The material used to construct roof decks, and the methods used to attach the deck to
the roof framing members can influence the likelihood of failure in high winds.
The material used to construct roof decks, and the methods used to attach the deck to
the roof framing members can influence the likelihood of failure in high winds.
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| OSB Sheathing |
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| Plywood Sheathing |
Roofing Materials
Plywood/OSB - The most common
roof deck types in residential
construction today are plywood and
Oriented Strand Board (OSB) decks.
Dimensional Lumber - Prior to the
introduction of plywood to the
construction industry (in the 1950's),
the most common roof decking
material was dimensional lumber or
tongue and groove (T&G) decking.
Dimensional lumber or T&G are
usually 4- to 8-inch wide boards that
are nominally 1-inch thick (3/4-inch
actual thickness) and are laid in a
fashion that is parallel to the ridge or
diagonal to the ridge. Dimensional
Lumber roof decks are not typically
used in today's construction because
of the higher labor costs.
Concrete - Concrete decks are roof
structures composed of cast-in-place
or pre-cast structural concrete
designed to be self-supporting and
integrally attached to the wall/support
system. These types of systems
typically get the largest credits from
insurance companies.
Plywood/OSB - The most common
roof deck types in residential
construction today are plywood and
Oriented Strand Board (OSB) decks.
Dimensional Lumber - Prior to the
introduction of plywood to the
construction industry (in the 1950's),
the most common roof decking
material was dimensional lumber or
tongue and groove (T&G) decking.
Dimensional lumber or T&G are
usually 4- to 8-inch wide boards that
are nominally 1-inch thick (3/4-inch
actual thickness) and are laid in a
fashion that is parallel to the ridge or
diagonal to the ridge. Dimensional
Lumber roof decks are not typically
used in today's construction because
of the higher labor costs.
Concrete - Concrete decks are roof
structures composed of cast-in-place
or pre-cast structural concrete
designed to be self-supporting and
integrally attached to the wall/support
system. These types of systems
typically get the largest credits from
insurance companies.
Roof Deck Attachment
Dimensional lumber decks are typically
stronger than plywood/OSB roof decks
because they are attached with more nails
than plywood/ OSB decks. Thus, even older
homes built before the introduction of
high-wind criteria into the local building
codes may qualify for wind insurance
credits.
The roof deck connection type can be
determined on existing buildings by using a
metal detector to locate the nails or screws.
Dimensional lumber decks are typically
stronger than plywood/OSB roof decks
because they are attached with more nails
than plywood/ OSB decks. Thus, even older
homes built before the introduction of
high-wind criteria into the local building
codes may qualify for wind insurance
credits.
The roof deck connection type can be
determined on existing buildings by using a
metal detector to locate the nails or screws.
The following is the type of deck connections for which insurance companies may give
credits.
The determination of roof deck attachment generally requires verification by a
construction professional or other inspector authorized by the insurance company. The
following items describe the typical roof deck attachment methods used in residential
construction. Each of the nail options refers to the size of the nail (commonly referred
to as a penny size (d)) and the spacing of nails along the framing members. The two
numbers refer to the spacing along the edges of the plywood and the spacing of nails
along the interior members of the plywood.
credits.
The determination of roof deck attachment generally requires verification by a
construction professional or other inspector authorized by the insurance company. The
following items describe the typical roof deck attachment methods used in residential
construction. Each of the nail options refers to the size of the nail (commonly referred
to as a penny size (d)) and the spacing of nails along the framing members. The two
numbers refer to the spacing along the edges of the plywood and the spacing of nails
along the interior members of the plywood.
8d Nails @ 6/6 - Roof deck is attached
with 8d (2.5" long) nails spaced at 6
inches on the edge of the sheathing and
the interior of the sheathing. This
connection pattern is seen mostly in
newer homes built to high wind standards.
Screws/Bolts - Instead of using nails to
attach the deck, some manufacturers are
now producing screw guns that can install
screws almost as fast as nails. Screws
typically have must greater pullout
resistance than equivalent lengths of nails.
8d Nails @ 6/12 - Roof deck is
attached with 8d (2.5" long) nails spaced
at 6 inches along the edge of the
sheathing and 12 inches in the interior of
the sheathing.
6d Nails @ 6/12 - Roof deck is
attached with shorter 6d (2" long) nails
spaced at 6 inches along the edge of the
sheathing and 12 inches in the interior of
the sheathing.
with 8d (2.5" long) nails spaced at 6
inches on the edge of the sheathing and
the interior of the sheathing. This
connection pattern is seen mostly in
newer homes built to high wind standards.
Screws/Bolts - Instead of using nails to
attach the deck, some manufacturers are
now producing screw guns that can install
screws almost as fast as nails. Screws
typically have must greater pullout
resistance than equivalent lengths of nails.
8d Nails @ 6/12 - Roof deck is
attached with 8d (2.5" long) nails spaced
at 6 inches along the edge of the
sheathing and 12 inches in the interior of
the sheathing.
6d Nails @ 6/12 - Roof deck is
attached with shorter 6d (2" long) nails
spaced at 6 inches along the edge of the
sheathing and 12 inches in the interior of
the sheathing.
| Click the photos to enlarge |
| © Bell Inspection Service 2007 |