At this point in my life, I do not believe typhoon-proofing
a house can be guaranteed. But damage can definitely be mitigated by adapting our
construction methodology to the threat. The Ph is the most typhoon-hit country
in the entire planet. I live in Sorsogon, one of six provinces in the Bicol
region. This area is generally more wet than other regions because most typhoons
come from east of the Ph as it makes its way to either Japan or China,
traversing Catanduanes.
In the last quarter of 2007, two typhoons of “signal
no.4” strength ravaged Bicol. ‘Milenyo’ hit Sorsogon in September, followed by ‘Reming’,
which devastated Albay a month after. Of course this was way ahead of ‘Yolanda’,
the super-typhoon that struck the Visayas last November, 2013.
The painful lessons of those 2 super-typhoons in 2007 taught the Bicolanos to adapt to the phantasmagoric havoc that their kind
can wreck.
Right after 'Milenyo', I undertook construction
of my house which was totaled. After a month, 'Reming' struck and ruined what
substantial repairs I had done. Add to this scourge the power outage that lasted several
months. Many were overwhelmed by the blight and hopelessness all around. But
life moved on and forward.
It’s a
blessing that I do construction regularly, so I took particular attention on
what parts of a house sustained the first damage that eventually caused a domino-effect on
the entire structure. I’ve been asked often how to typhoon-proof a house. Here
are my Top 5 Tips:
1. Limit Your Openings.
I
looked at the direction of the mighty wind
blasts. In my place it came from the West side. So I made no openings
there
except for the main door and a window beside it. I used steel casement
windows on the weakest side, not big glass on aluminum frames to
minimize the danger from glass debris in a storm. In the event glass is
shattered, I need to replace only small glass panes. My garage, which
was in front
of the main door, had sheet roofing. I protected this by casting in
place a 0.60
meter (24 inches) wide parapet wall along the entire front.
Plan your Roof. If it goes, practically your
whole house goes. So my tips include several ideas on the roof alone.
2. Limit Your Roof Eaves. (Bolada)
I observed that most Ph houses try to make
the roof eaves as lengthy as possible (sometimes reaching up to 1.2 meters) to
economize, since long eaves provide shade in summer and cover during rains. Try
not to exceed a 0.60 meter eave length. Strong winds will hold on the eaves with
devastating uplift force. It is very important to ensure that no portion of the
eaves all around the house is left without a ceiling (kisame). Additionally, I protected the roof by casting in place a 0.60
meter (24 inches) wide parapet wall along its entire perimeter.
3. Exaggerate Your Trusses.
The typhoons ravaged a lot of forest areas
that in 2008 a moratorium was issued to allow the use of timber obtained from
fallen trees. I used hardwood derived from this. But if your area is scarce in
wood, use steel trusses. I shortened the spacing between my main trusses. I
exposed my wood trusses by putting my plywood ceiling right beneath the roof
(and the heat insulation, if you have any). The reason is that once you hide
your trusses underneath the ceiling, it is very hard for you to check them
later.
Note that there are 2 things to be aware of: (a) the bottom chord of
trusses is subjected to heavier stresses; and (b) you must re-visit your truss
connectors at some future time after construction. In my case, since there was
urgency when I constructed, I used nails to connect my truss members. Later I
revisited and changed them to nuts and bolts.
4. Exaggerate Your Purlins.
Since wood is not available in most urban
areas, most purlins are C-section steel sheet channels 3” to 6” wide.
Exaggerate purlin spacing as well. So much discussion was made after the
super-typhoons that the first cause of flying G.I. roofs was that the nuts and
bolts that fastened them to the purlins were dislodged due to constant
vibration from successive wind blasts.
In case you are using steel purlins, avoid
using Tek screws that drill their own hole and then tap threads to combine two
or more pieces of material (in this case, the roof sheet and the purlin).
Rather, fasten your roof in this manner: Use a bolt that goes through the roof,
then flat washer, then lock washer, then nut, then lock washer, then nut. Spend
extra effort on using 2 nuts and 2 lock washers while installing heavy-gauge
sheet roof. You may not get the chance to add this later, especially if your
ceiling hides your trusses.
At any rate, I used lumber for my purlins because lumber was plentiful after the super-typhoons. I exaggerated by
using 3”x3” wood purlins spaced every 1 foot. I pre-drilled the roof sheet but not
the wood to allow the Tek screws to ‘bite’ on the purlins.
5. Limit the slope of your Roof.
This is a rather touchy matter since you have
to balance aesthetics with strength. As a rule, the bigger the slope, the
stronger. But too steep a slope will be an eye-sore. You have to find out by
trial and error what works best for your house’s dimension. I used a 38-degree
slope because it looked pleasant, but I will go no higher than 41 degrees
because I feel that going more than that will look bad. Sometimes you have to blend
different slopes, especially when your roof bends in different directions.
Be safe.
