Making
Tierrasanta Fire Safe - Fire Safe Homes; Winners and Losers
Maintenance of the 100 foot defensible space as prescribed in the
city Brush Management Guide For Private Property, February 2006
http://www.sandiego.gov/fireandems/
reduces the fuel helping to reduce the embers, firebrands and
thermal impact to a home. This 100 foot defensible space is consists
of two zones the Zone 1 typically extends 35 feet from the structure
in all directions. Zone 2 is the remaining 65 feet up to100 feet
from the structure. Maintaining the 100 foot space provides firemen
with better access to a brush fire and the intensity of the fire is
reduced to one-half due to the 50% thinning requirement
When
entering a neighborhood during a wildfire, firefighters must make
decisions to size up a home for its defensibility. The result of
this process is identification of homes or structures that are the
‘winners’ and those that are the ‘losers’. Firemen may not be able
to tell in the ‘heat of a fire’ which homes have maintained 100 foot
Defensible Space brush thinning. So they may look for other property
characteristics, like those discussed in the December 2007 Tierra
Times article, including enclosed eaves and class ‘A’ roof coverings
(e.g., steel, asphalt or tile and not shake). In addition,
firefighters must have accessibility to the property from the street
for themselves and equipment. This article addresses details of the
Defensible Space Zone 1, sometimes termed the Lean, Clean, Green
Area that begins at the perimeter of the home and extends in a
35-foot radius from the base of a home. This area requires the
greatest attention to fuel reduction. It should be a renewed focus
of Tierrasantans for fuel reduction and other ‘lean, clean and
green’ aspects to make our homes more defendable and should help the
chances that more of our homes are ‘winners’.
Maintain a Non-combustible Area Around Your Home
Each
home should have a 3-foot wide Non-combustible Area around the
perimeter of the home. Any planted sections of this 3-feet wide area
should be irrigated with an automatic irrigation system. Plants next
to homes can be a wick-like fuel source if not maintained properly
for thinning, height, breadth, separation from other plants and
clearance from the structure. Many ornamentals, junipers, and ice
plant leave flammable woody remnants internal to the new growth
which can accumulate year after year in addition to being hostels
for rodents and insects. During a wildfire flying embers may collect
in this area. A fire burning in plants or wood mulch next to a
stucco home can allow fire entry through the drip edges embedded in
the bottom or base of walls. These drip edges are installed to allow
moisture that may accumulate behind the stucco to weep out helping
to prevent mold and deterioration of the stucco. Wood siding on a
home is very inviting to vegetation especially climbing vines which
act like a net that can easily catch embers and fire brands.
Improper sealing of siding, even fire resistant, can allow flames to
draft into a home through gaps. A firefighter may attack a fire in
vegetation adjacent to an exterior wall or at the base of a home and
not detect a smoldering fire within the wall caused by flames
entering through the drip edges or gaps. Vents installed in the
lower outside wall of garages and in homes with crawl spaces beneath
can allow fire to be breathed into a home or garage from burning
plants that are adjacent to or concealing them. Most of these vents
in Tierrasanta are screened with ¼ inch mesh and as with attic vents
should have less than 1/8 inch mesh. It is recommended that
herbaceous plants such as ground covers and flowers or landscape
rocks and hardscape surfaces and certainly no trees be considered
for creating this non-combustible 3-feet wide area. Tierrasanta
homes should not have any portion of a tree that extends within 10
feet of a chimney and a better practice is to have no
portion of a
tree within 10 feet of a
structure. The actual spacing and trimming parameters will depend
on the homeowner’s degree of property risk he wishes to assume.
Vinyl windows are popular because they can be more attractive and
can provide better sound and heat/cold insulation. Vinyl windows
resist combustion up to 325 degrees, but can melt or burn if a flame
source is near. So burning plants, other fuel sources or radiant
heat in close proximity a vinyl window may generate enough heat to
melt or droop and inflame a vinyl window and possibly allow interior
home flame penetration. Newer vinyl windows are internally
reinforced with metal supports which are installed to help prevent
drooping of the vinyl frame. Aluminum frame windows melt at 1400
degrees and may provide a better flame seal for homes than vinyl
frame windows. In both cases the window glass may shatter due to
heat prior to supporting frame structure failure. New windows are
required to have more than one pane of glass and at least one pane
must be tempered glass. . These windows have multiple sheets of
overlapping glass with a sealed inert gas-filled voids sandwiched
between for insulation. Tempered glass is less likely to shatter
but even multiple pane windows may have at least one pane break or
shatter due to heat exposure. Installation of non-flammable or fire
resistant shutters can be a home saving feature no matter the kind
of windows that are installed.
Maintain a Perimeter Access Area
A
Perimeter Access Area is critical to ensure that firefighters with
equipment can easily access the properties. This it the area
overlapping the Non-combustible Area extending 10 feet from the base
of the home into the 35 foot defensible space area. Homes in
Tierrasanta may be very close to each other with walkways or access
spaces between the homes from the front of the homes to the back on
both sides. Access between houses, in many cases, are less than
4-feet wide with only 8 feet total only between the houses. So the
Perimeter Access Area may extend on to the neighbors property.
Residents may store trash cans, gardening equipment or other items
in these walkway areas that can hamper firefighters. These items
themselves may be flammable. The city provided trash cans, which may
take up most of the 4-foot wide access space, are made of plastic
which can melt and burn similar to vinyl windows, if a flame source
is present,. Some homes have very restricted access along the sides
of their homes due to plants, trees, attached gateless fences or the
presence of stored items. Residents should keep the access along
the side of their homes clear of any obstacle that would prevent or
inhibit access by firefighters. If the community is threatened with
fire and if time permits residents should move these trash cans to
their garage for storage until the threat is over. If there are
gates at the side accesses and evacuation is necessary they could be
left open to allow a clear view or at least left unlocked.
When
attached to homes wooden fences can function like
fuzes and lead fire to the structure and
perimeter vegetation which in turn could flame-up into the eaves.
Wood fences, if not completely replaced, should at least have the
first five lineal feet that is connected to the home removed or
replaced with a fire resistant product. A five foot a fire resistant
gate in place of the fence segment is also an option. Flammable
gates should not be hinged to the home or garage. Continuous path
vegetation e.g., hedges, or “fire ladder” acts much like wood
fences. They may stretch from the property line and terminate at the
structure and may have more flame height and burn faster than wood
fences. Firefighters will be delayed in the attack on home fires
while dealing with a burning wooden fence or fire ladders.
Many
homeowners in Tierrasanta have added decks on their properties.
These decks are not the starting point when measuring 100 foot
defensible space distance unless the decks are attached to the home.
For example, if a 20 foot deck is constructed 5 feet from a home,
cutting Perimeter Access Area in half, the defensible space
measurement would still be measured from the home. If the deck
(patio cover or balcony) is connected to the home, the defensible
space requirement is extended from the home by the length of the
deck or in this case to 120 feet. Data from the recent fires of 2007
showed that in one area 57 of 67 homes were lost due to ignited
decks that were built to extend over canyon slopes. These decks,
coined ‘cliffhangers’ by fire professionals (some extending into the
65 foot Zone 2 and public property), were responsible for
transferred embers or radiant heat that destroyed the homes.
Defensible space or not, decks that are not constructed with fire
resistant materials and not protected from underside are as
vulnerable to a wildfire as a wood roof or any other stack of dry
wood. Once engulfed a deck becomes a relay point spewing out embers,
firebrands and radiant heat to a home. In addition, a burning deck
may inhibit firefighters from having immediate access to fires in
the wild land beyond as well as costing valuable time when the house
itself is burning. Lawn furniture on lawns, patios or decks may be
flammable also and could be obstacles to firefighters. If evacuation
may be necessary and time permits patio furniture should be stored
in the garage with the trash cans.
There are other risky home characteristics and many often going
without notice such as; an upper vent in the sidewall of a garage
with the same large mesh problem as attic and crawl space vents and
perhaps concealed by tall trees (trees to avoid—junipers, pine
trees, eucalyptus, and Italian cypress); a doggie door can usher in
embers and fire brands; and the single swing-up garage doors with
gaps at the sides and top can draw in embers as the house vents in
and out during a wildfire. Don’t forget to have house numbers
visible from the street either. This article addressed some
considerations in the 35 foot Zone 1 component of the required
Defensible Space that if addressed by homeowners could not only
provide better access by our firefighters to get to the structures,
but also make it easier to identify a home as a ‘winner’ and in turn
help to establish all of Tierrasanta as a community of winners. This
article with linkable resources for other tips or actions that
homeowners can take can be found on the Tierrasanta Fire Safe web
site at http://campbellot.com/fireSafe_tierrasanta.
http://www.livingwithfire.info/beforethefire/index.php
http://www.slate.com/id/2178805
http://www.sandiego.gov/fireandems/