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The roof
covering, and the deck beneath it, form
one of your home's critical shields of
protection from high winds and rain.
Unfortunately, this shield is often the
first to be lost during high winds.
Loss of the roof covering, such as
shingles, tiles or metal panels makes
the house more vulnerable to water
damage. The loose roofing inevitably
becomes wind-borne projectiles that can
damage other structures.
But while the loss of roofing can make
your home vulnerable to water
infiltration, loss of the roof's
sheathing, often referred to as decking,
can result in excessive damage to your
home and your possessions.
As wind blows over the roof, uplift
forces pull at the roof. These uplift
forces try to pull off the roof covering
and the roof deck. When the roof decking
is blown off, the inside of your home
becomes completely exposed to the
elements and trusses or rafters may
become unstable and the entire roof may
collapse.
The following techniques can be used
during roof installation on both new and
existing homes, and are best performed
by a licensed, professional roofing
contractor.
Install a roof deck of solid plywood,
5/8" thickness, to maximize wind and
windborne debris resistance with 10d
common nails spaced at 4 inches along
the panel edges and every six inches in
the field of the plywood panel. Make
sure that the nails penetrate the
decking directly into the roof framing.
In your existing home, be sure to look
in the attic to confirm that the roof
decking is properly nailed to the roof
framing. If you can see nails along the
sides of rafters or trusses, where the
nail penetrates the decking, your roof
deck is probably not securely attached.
Create a secondary water barrier by
installing self-adhering flashing tape
or modified polymer bitumen strips,
commonly called "peel and seal," over
the joints in your roof deck. This will
help keep out the rain in the event the
roof covering is damaged or destroyed by
severe weather.
Install one layer of #30 underlayment,
sometimes called felt paper, over the
roof decking and secondary water
barrier. The felt helps with drainage in
the event water gets under the roof
covering.
Install a roof covering that has been
tested to ASTM D 3161 for wind
resistance and UL 2218 for impact
resistance. Be sure to specify these
standards and look for labels on the
products confirming these standards
because ordinary roofing materials may
not look any different from the wind
resistant versions.
Finally, you can significantly increase
the roof's resistance to uplift from the
wind by applying a bead of construction
adhesive using a caulking gun along both
sides of the intersection of the roof
decking and the rafters or trusses. Be
sure to look for an adhesive that has
been tested to specific levels:
APA AFG-01
ASTM D 3498)
Visit www.flash.org or call toll-free
(877) 221-SAFE for more information
about protecting your home from
disaster.
Copyright 2004 Federal Alliance for Safe
Homes -- FLASH, Inc. All rights
reserved. |
