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Thursday, 31 May 2007 |
During a hurricane, homes may be damaged or destroyed by high winds and high waves. Debris can break windows and doors, allowing
high winds inside the home. In extreme storms, such as Hurricane Andrew, the force of the wind alone can cause weak places in your home to
fail.
After Hurricane Andrew, a team of experts examined homes that had failed and ones that had survived. They found four areas that should be checked for weakness—the roof, windows, doors, and if you have one, garage door. In this brochure, we discuss some things you can do to help make your home stronger before the next hurricane strikes. You may need to make some improvements or install temporary wind protection.
It is important that you do these projects now, before a hurricane threatens. While these projects, if done correctly, can make your home safer during a hurricane, they are no guarantee that your home won’t be damaged or even destroyed. If you are told by authorities to evacuate, do so immediately, even if you have taken these precautions.
The Roof
During a windstorm, the force of the wind pushes
against the outside of your home. That force is
passed along from your roof to the exterior walls
and finally to the foundation. Homes can be damaged
or destroyed when the energy from the
wind is not properly transferred to the ground.
The first thing you should do is determine what
type of roof you have. Homes with gabled roofs
are more likely to suffer damage during a hurricane.
A gabled roof looks like an A on the ends,
with the outside wall going to the top of the roof
. The end wall of a home with a
gabled roof takes a beating during a hurricane, and
those that are not properly braced can collapse,
causing major damage to the roof.
In most homes, gabled roofs are built using
manufactured trusses. Sheets of roof sheathing,
often plywood, are fastened to the trusses with
nails or staples, and roofing material is fastened to
the sheathing. In many cases, the only thing holding
the trusses in place is the plywood on top.
This may not be enough to hold the roof in place
during a hurricane. Installing additional truss bracing
makes your roof ’s truss system much stronger.
To inspect your roof ’s bracing, go into the attic.
While working in your attic, you should wear
clothing that covers your skin, work gloves, a hat,
eye protection, and a dust mask. If your attic does
not have a floor, be careful to walk only on the
wood joists, or install boards wide enough to walk
on as you work. Notice how the plywood is
attached to the truss system. If most of the large
nails or staples coming through the sheathing have
missed the trusses, consider having the sheathing
properly installed.
Truss bracing
In gabled roofs, truss bracing usually consists of
2´4s that run the length of the roof. If you do not
have truss bracing, it should be installed. You can
do this yourself or hire a professional. Install 2´4s
the length of your roof, overlapping the ends of the
2´4s across two trusses. Braces
should be installed 18 inches from the ridge, in the
center span, and at the base, with 8 to 10 feet
between the braces. Use two 3-inch, 14-gauge
wood screws or two 16d (16 penny) galvanized
common nails at each truss. Because space in attics
is generally limited, screws may be easier to install.
Gable end bracing
Gable end bracing consists of 2´4s placed in an
“X” pattern from the top center of the gable to the
bottom center brace of the fourth truss, and from
the bottom center of the gable to the top center
brace of the fourth truss. Use two
3-inch, 14-gauge wood screws or two 16d galvanized
common nails to attach the 2´4s to the
gable and to each of the four trusses.
Hurricane straps
There are many types of roof design. Regardless of
your type of roof, hurricane straps are designed to
help hold your roof to the walls. While you are in
the attic, inspect for hurricane straps of galvanized
metal. Hurricane straps may be difficult
for homeowners to install. You may need to
call a professional to retrofit your home with hurricane
straps. Check with your local government
building officials to see if hurricane straps are
required in your area.
Exterior Doors and Windows
The exterior walls, doors, and windows are the
protective shell of your home. If your home’s protective
shell is broken, high winds can enter and
put pressure on your roof and walls, causing damage.
You can protect your home by strengthening
the doors and windows.
Double entry doors
Most double doors have an active and an inactive
or fixed door. Check to see how the
fixed door is secured at the top and bottom. The
bolts or pins that secure most doors are not strong enough .
Some door manufacturers provide reinforcing
bolt kits made specifically for their doors. Check
with your local building supplies retailer to find
out what type of bolt system will work for your
door. The door bolt materials should cost from
$10 to $40, depending on the type and finish.
Doors with windows will need additional protection
from flying debris. See the section on storm
shutters for how to protect windows.
Double-wide garage doors
Double-wide (two-car) garage doors can pose a
problem during hurricanes because they are so
large that they wobble as the high winds blow and
can pull out of their tracks or collapse from wind
pressure. If garage doors fail, high winds can enter
your home through the garage and blow out
doors, windows, walls, and even the roof.
Certain parts of the country have building codes
requiring garage doors to withstand high winds.
You should check with your local government
building officials to see if there are code requirements
for garage doors in your area. Some garage
doors can be strengthened with retrofit kits.
Check with your local building supplies retailer to see if a retrofit kit is available
for your garage door.
You can expect to pay from
$70 to $150 to retrofit your
garage door.
Many garage doors can be
reinforced at their weakest
points. Retrofitting your
garage doors involves
installing horizontal bracing
onto each panel. This
horizontal bracing can be
part of a kit from the garage
door manufacturer. You may
also need heavier hinges
and stronger center supports
and end supports for
your door.
Check the track on your
garage door. With both
hands, grab a section of
each track and see if it is
loose or if it can be twisted.
If so, a stronger track
should be installed. Make
sure that it is anchored to
the 2´4s inside the wall with
heavy wood bolts or properly
attached to masonry with
expansion bolts.
After you have retrofitted
your door, it may not be balanced.
To check, lower the
door about halfway and let
go. If it goes up or down, the
springs will need adjusting.
The springs are dangerous
and should be adjusted by a
professional.
If you are unable to retrofit
your door, you can purchase
specially reinforced garage
doors designed to withstand
winds of up to 120 miles per
hour. These doors can cost
from $400 to $450 (excluding
labor) and should be
installed by a professional.
Storm shutters
Installing storm shutters
over all exposed windows
and other glass surfaces is
one of the easiest and most
effective ways to protect
your home. You should
cover all windows, French
doors, sliding glass doors,
and skylights. There are
many types of manufactured
storm shutters available.
For more information
on manufactured shutters,
check with your local building
supplies retailer. If you
install manufactured shutters,
follow the manufacturer’s
instructions carefully.
Before installing shutters,
check with your local building
official to find out if a
building permit is required.
It is important that you
have your shutters ready
now, and that you mark and
store them so they can be
easily installed during a
hurricane watch.
Plywood shutters that you
make yourself, if installed
properly, can offer a high
level of protection from flying
debris during a hurricane.
Plywood shutters can be
installed on all types of
homes.
Measure each window and
each door that has glass,
and add 8 inches to both the
height and width to provide
a 4-inch overlap on each
side of the window or door.
Sheets of plywood are generally
4´8 feet. Tell your
local building supply retailer
the size and number of
openings you need to cover
to determine how many
sheets to buy.
To install plywood shutters
you will need bolts, wood or
masonry anchors, large
washers, and 5/8 - inch
exterior-grade plywood. For
windows 3 feet by 4 feet or
smaller installed on a wood
frame house, use 1/4 -inch
lag bolts and plastic-coated
permanent anchors. The lag
bolts should penetrate the
wall and frame surrounding
the window at least 1 3/4
inches. For larger windows,
use 3/8 –inch lag bolts that
penetrate the wall and
frame surrounding the window
at least 2 1/2 inches.
For windows 3 feet by 4 feet
or smaller installed on a
masonry house, use 1/4-inch
expansion bolts and galvanized
permanent expansion
anchors. The expansion bolt
should penetrate the wall at
least 1 1/2 inches. For larger
windows, use 3/8 –inch
expansion bolts that penetrate
the wall at least 1 1/2
inches. The tools you will
need are a circular or hand
saw, a drill with the appropriately
sized bits, a hammer,
and a wrench to fit the
bolts. To be safe, use eye
protection and work gloves.
Cut the plywood to the measurements
for each opening.
Drill holes 2 1/2 inches from
the outside edge of the plywood
at each corner and at
12-inch intervals. Drill four
holes in the center area of
the plywood to relieve pressure
during a hurricane.
Place the plywood over the
opening and mark each hole
position on the outside wall.
Drill holes with the appropriate
size and type of bit
for the anchors. Install the
anchors, the plywood, and
the bolts to make sure they
fit properly.
On wood-frame houses,
make sure that the anchors
are secured into the solid
wood that frames the door
or window and not into the
siding or trim. Mark each
shutter so you will know
where it is to be installed
and store them and the
bolts in an accessible place.
If the opening is larger than
one sheet of plywood, you
will need to make shutters
with 2´4 bracing. This bracing
can be two 2´4s at the
middle and bottom of the
two sheets of plywood, evenly
spaced, with the 2-inch
side attached to the inside
of the storm shutter. Attach
the 2´4s to the outside of
the storm shutter with 2-
inch, 10-gauge wood screws
before installing the shutter.
The recommendations in
this brochure are not
intended to replace local
building code requirements
or to serve as the only
options for protecting your
home from hurricane wind
damage. For more information
on protecting your
home from hurricane wind
damage, contact your local
building official; your local
building supply retailer; or
a building professional,
such as an engineer, architect,
or experienced contractor.
The recommendations in
this article are not intended
to replace local building
code requirements or to
serve as the only options for
protecting your home from
hurricane wind damage.
For more information on
protecting your home from
hurricane wind damage,
contact your local building
official; your local building
supply retailer; or a building
professional, such as an
engineer, architect, or experienced
contractor.
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