|
|
Click here to download a PDF version of this checklist.
|
Investigating the Roof-to-Wall Connection:
Inspection: In your attic or in an unfinished garage, use a flashlight
to look at the connection between the trusses or rafters and the outside
walls of the house. Try to determine whether you can see any indication
of metal straps. If you see straps, check to see whether they are on every
connection or every other connection. Look for the following:
|
|
- Is there any sign of a metal strap connecting the roof rafters or trusses
to the top of the wall?
[ ] Yes
[ ] No
- If there are metal straps, are they installed at the end of every truss
or rafter or to the end of every other truss or rafter?
[ ] Yes - Every Truss/Rafter
[ ] No - Every Other Truss/Rafter
- Do the straps wrap over the top of the rafters?
[ ] Yes - I have trusses or the straps wrap over rafters
[ ] No - I have rafters and the straps do not wrap over the top of the rafters.
|
|
|
|
Assessment:
If you answered "No" to question 1, your home is in need of hurricane straps.
The least expensive thing you can do (as a start) that will reduce your
risk of loss of the roof is to protect all large windows and doors because
this will reduce the chance that wind forces will also be pushing up and
out from the inside of your house. You should make sure that your garage
door is protected or replaced with an appropriate wind rated one if you
don't already have one. Protecting your windows and doors could mean the
difference between the home keeping its roof on or loosing it when the
winds climb above category 1 strength. You should definitely plan on evacuating
if a category 2 or above storm is threatening your area, even if you protect
the windows.
If the answers to all of the questions are "Yes", your roof is probably
reasonably well strapped to the walls and you should concentrate on other
areas of vulnerability, including anchorage of the walls and wall strength
as outlined below.
If the answer to question 1 is "Yes" but the answer to question 2 and/or 3
is "No", you may want to consider additional work on connecting
the roof to the walls if it can be done inexpensively. Retrofitting the
roof to wall connection is particularly important if your roof has a fairly
low slope, the home is more than about 30 feet wide, you have open (unobstructed
) areas around your house, and you live in an area where the 3-second gust
design wind speed is greater than 120 mph. Again, the least expensive
thing you can do (as a start) that will reduce your risk of loss of the
roof is to protect all large windows and doors because this will reduce
the chance that wind forces will also be pushing up and out from the inside
of your house. You should make sure that your garage door is protected
or replaced with an appropriate wind rated one if you don't already have
one. Protecting your windows and doors could mean the difference between
the home keeping its roof on or loosing it when the winds climb above category
2 strength. You should definitely plan on evacuating if a category 3 or
stronger storm is threatening your area, even if you protect the windows.
Investigating the Wall Strength:
Background and Suggestions: Generally, it will be pretty difficult
to determine how well your walls are built or anchored to the foundation
unless you open up part of an exterior wall. If you end up having to repair
drywall on an exterior wall or are having your home re-sided, you have
an opportunity to check the wall construction details. You may also be
able to gain some insight into the likely wall construction by talking
with the building official in your community or older well established
builders and asking what was typically done at the time your home was built.
Other indirect clues include the absence of hurricane straps connecting
the trusses or rafters to the top of the wall or straps that are installed
on every other truss or rafter connection. If either of these cases exists,
chances are that you don't have a particularly strong wall structure
and that it may not be very well anchored to the foundation. If you really
want to know what your walls are made of, and don't mind replacing some
wallboard, you could cut out a small section of wallboard on the inside
of an exterior wall in an out of the way place. Finally, in homes built
before the 1970's you may well have lath boards and plaster or plank siding
with little more than tar paper behind the exterior sheathing. In the
1070's plywood began catching on but many homes only had sheathing at the
wall corners and some may only have fiber board. Consequently, you may
need to look at an exterior wall near one of the corners of the house and
near the middle of one of the exterior walls.
Anchoring of the bottom of the wall to the foundations requires the uplift
loads to be transferred into the bottom plate of the wall and from that
plate into the foundation (slab on grade) or into the floor system and
then into the foundation (elevated wood frame floor). The transfer of
loads into the bottom plate can be accomplished either by the exterior
sheathing if it is plywood or OSB or through straps between the studs and
the bottom plate or a combination of the two methods. In areas where the
3-second gust design wind speed is greater than 120 mph, the latest high
wind construction guides for slab on grade construction require straps
embedded in the concrete and nailed to the bottom plate or the wall studs,
or 5/8-inch diameter anchors bolts spaced at 18 inches or less. They
also require 3-inch by 3-inch by 1/8-inch thick washers between the nuts
and the bottom plate if anchor bolts are used. If you have a wood frame
floor, anchor bolts don't work. Straps or other methods have to be used
to transfer loads from the wall to the band joists around the floor system
and from them into a sill plate which is anchored to the foundation. If
you have framed floors, you will be well advised to seek professional help
to come up with cost effective solutions.
Finally, laboratory testing and engineering analysis indicate that the
ends of the walls should have large anchors called hold downs (sometimes
threaded rods are used that run the full height of the wall). Except for
a few parts of the country, it is unlikely that you will find these if
your house was built before 1995.
Inspection: The following questions assume slab on grade construction.
For homes with wood frame elevated floors, the exterior walls have to
be connected by straps or sheathing to the rim joists (a band of wood members
that frame around the edge of the wood frame floor system) and the rim
joists have to be connected to the sill plate (pressure treated wood member
lying flat on the top of the foundation wall and anchored to the foundation).
You should be looking for anchor bolts that attach the sill plate to
the foundation. Because the floor framing helps tie the system together,
the anchor bolt spacing for the sill plate (below a wood frame floor)
can be about twice the spacing indicated in the questions below.
Look at the wall sheathing:
|
|
- Is the sheathing plywood or oriented strand board (OSB) or is it fiberboard
or foam?
[ ] Yes - Plywood or OSB
[ ] No - Foam board, Fiber board, or Insulation board
- Is the wood sheathing continuous across the whole wall or is it only
in the corners with the rest foam board or fiber board?
[ ] Yes - Wood sheathing continuous across the whole wall
[ ] No - Wood sheathing only at the corners
- Does the wood sheathing continue all the way to the top of the top
plate if the top plate is not strapped to the wall studs?
[ ] Yes - The top plate is strapped to the studs or the sheathing continues all the way to the top of the top plate
[ ] No - The top plate is not strapped to the wall studs and the sheathing does not go all the way to the top of the top plate
- Are horizontal joints between sheets of plywood or OSB blocked or un-blocked?
[ ] Yes - blocked
[ ] No - unblocked
- Are the nails at least as close as 6" along the bottom of the sheets
into the bottom plate and along the edges of the sheets into the wall studs?
You can check this using the metal sensor on a stud finder that has
this option. Drag the stud finder along the studs with the metal detection
turned on and mark each location where the sensor indicates a nail.
[ ] Yes - nail spacing is about 6" or less around the edges of the wall sheathing
[ ] No - nail spacing is consistently more than 6" around the edges of the wall sheathing
|
|
|
|
Assessment:
If the answers to all of the questions are "Yes", you have a strong
well connected wall and you can concentrate on other vulnerability issues.
If the answer to all of the questions is "No", your walls are not
very strong and not well connected. The least expensive thing you can
do (as a start) that will reduce your risk of having your house break apart
in a hurricane is to protect all large windows and doors. You should make
sure that your garage door is protected or replaced with an appropriate
wind rated one if you don't already have one. Protecting your windows
and doors could mean the difference between finding your home still standing
or having parts or all of it collapse when the winds climb above category
1 strength. You should definitely plan on evacuating if a category 2 or
above storm is threatening your area, even if you protect the windows.
If your answers are a mixture of "Yes's" and "No's", then you have
some wall resistance which when combined with the drywall connections may
help your home survive stronger winds than a home with all "No" answers.
Again, the least expensive thing you can do (as a start) that will reduce
your risk of having your house break apart is to protect all large windows
and doors. You should make sure that your garage door is protected or
replaced with an appropriate wind rated one if you don't already have one.
Protecting your windows and doors could mean the difference between
finding your home still standing or having parts or all of it collapse
when the winds climb above category 2 strength. You should definitely
plan on evacuating if a category 3 or above storm is threatening your area,
even if you protect the windows.
Inspection:
Look at the connection of the wall studs to the bottom plate and the
connection of the bottom plate to the foundation: The latest high wind
anchorage uses 5/8" anchors with 3" by 3" washers that are at least 1/8"
thick. Older installations used 1/2" anchors that were frequently shorter
so that there was less embedment into the concrete and were frequently
installed without a great attention to detail. The washers were frequently
just regular round steel washers for 1/2 " bolts. Recent tests have demonstrated
the importance of the larger washers when winds approach design values.
|
|
- Do you have anchor bolts or straps embedded in the concrete?
[ ] Yes
[ ] No
- Is the distance between the anchor bolts or straps 24 inches or less? 18 inches or less if the 3-second gust design wind speed in your area is greater than or equal to 120 mph.
[ ] Yes
[ ] No
- If you have anchor bolts, are they at least 5/8-inch in diameter and do they have 3-inch by 3-inch by 1/8-inch thick washers between the nuts and the bottom plate?
[ ] Yes - or I have straps holding down the bottom plate or connected to the studs
[ ] No - the bolts are smaller than 5/8-inch and/or they have washers that are smaller than 3" by 3"
- Do you have large anchors (hold downs) at the ends of the walls or threaded rods that run the full height of the wall?
[ ] Yes
[ ] No
|
|
|
|
Assessment:
If the answers to all of these questions are "Yes", you have well
anchored walls that likely meet the latest high wind standards. If the
roof is also well attached to the top of the walls and the walls are well
built (first two sets of questions), it is likely (unless your home is
hit by surge) that your home will still be standing, even after a major
hurricane. But, you may still suffer water damage, particularly if your
roof covering or windows and doors are damaged. Consequently, you should
focus your attention in those areas.
If your answer to the first three questions is "Yes", but your answer
to the last question is "No", you still have a pretty well anchored house
and it is likely that the home will still be standing after all but the
most intense hurricanes.
If all of your answers were "No", your house is not well anchored
to the foundation and it may suffer structural damage and be moved off
its foundations in a strong hurricane. You should plan on evacuating if
a category 2 or higher hurricane threatens your area.
Back to Wood Frame Walls
Back to main structural page
|
