High Wind Provisions of the Building Code:
According
to the 8th edition of the Building Code we must design to resist 110
mph winds for our area along Buzzards Bay, which is upper limit of a category 2 hurricane. And
according to my research that is the typical hurricane that strikes
this region. For a listing of wind speeds in Massachusetts go here and find table R301.2(4).
In the 8th edition (2009 IRC) Section R301.2.1.1 there are six design manuals/methods referenced by the Building Code
for high wind designing in the 110 mph Basic Wind Speed Zones:
1. American Forest and Paper Association (AF &PA) Wood Frame Construction Manual for One- and Two-Family Dwellings (WFCM); or
2. International Code Council (ICC) Standard for Residential Construction in High Wind Regions (ICC-600); or
3. Minimum Design Loads for Buildings and Other Structures (ASCE-7); or
4. American Iron and Steel Institute (AISI), Standard for Cold-Formed Steel Framing-Prescriptive Method For One- and Two-Family Dwellings (AISI S230).
5. Concrete construction shall be designed in accordance with the provisions of this code.
6. Structural insulated panel (SIP) walls shall be designed in accordance with the provisions of this code.
Massachusetts amended section R301.2.1.1 to include the Guide to Wood Construction in High Wind Areas, and the use of the Massachusetts Checklist for Compliance (click this link to download the WORD document) to demonstrate compliance with the high wind provisions of the Building Code.
The
Wood Frame Construction Manual 1995 edition was written after Hurricane Andrew. It
was the first manual to actually address wood construction with regards to
the physical forces homes must resist during a hurricane or high wind event. It is full of
tables, charts and diagrams used to perform high wind calculations for
the proper design of homes to resist high wind forces. AF&PA has released the 2012 edition of the Wood Frame Construction Manual.
After
Hurricane Katrina the American Forest and Paper Association came out
with the “Guide to Wood Construction in High Wind Areas for One- and
Two-family Dwellings”. Basically they took all of the 110-mph wind
information from the Manual and placed it in an easy to follow guide that can be used by builders and designers without the need for an engineer's understanding of the Manual.
The Board of Building Regulations and Standards adopted this Guide, and created the
Massachusetts Checklist for Compliance as a prescriptive method of
complying with the high wind provisions of the building code. According
to the BBRS Official website (see question #3) a home designed according to the Guide and
Compliance Checklist need not be certified by a registered engineer or
architect for compliance with the high wind requirements. They may still need an engineer's certification if the foundation is within a Flood Hazard, Zone, steel beams are installed or other structural reasons. By meeting the Guide and Compliance Checklist many of metal
connectors required by the Wood Frame Construction Manual may be
eliminated.
With knowledge of the Guide and the Compliance
Checklist a designer can make simple changes in their designs for
compliance thus reducing the cost of construction. Its not that the
metal connectors are expensive, it’s the labor involved in their
installation that adds up.
How does wind affect your home?
Click on the Picture Below to Find Out.
What about all of these metal connectors?
Metal connectors have become more common place in residential construction following the adoption of the High Wind Codes. In fact there are prescriptive requirements for metal tie straps to connect an upper floor to a lower one, wall studs to sill plates and headers to studs. There are areas you can not get away from using them, i.e., attachment of the roof assembly to the walls. The Wood Frame Construction Manual also requires metal holdown connectors at building corners to attach the dwelling to the foundation.
The 8th edition One- and Two-Family Building Code is based upon the 2009 International Residential Code (IRC) with Massachusetts amendments. These are two separate books that you must use to determine building code requirements. Since the development of the 2006 IRC the code has allowed the use of wood sheathing and nails to resist the combined uplift and shear forces on wall. A Google search of "combined uplift and shear" will find many links. In fact the International Code Council, developers of the IRC Code also developed ICC 600 Standard for Residential Construction in High Wind Regions. Combined uplift and shear is shown in the Special Design Provisions for Wind and Seismic (ANSI/AF&PA SDPWS-2008) by the American Forest & Paper Association, developers of the Wood Frame Construction Manual. You can also check out APAWOOD.ORG for additional information.
Meeting the High Wind Codes can be accomplished with methods more in keeping with traditional construction techniques.
But I don't wanna change ......
People
never like change. We like to whine when we have to do things
differently, or learn something new. It's human nature to complain. We
like to do today what we did yesterday. But if we do today what we did
yesterday, how can we expect to have different results tomorrow than we did today?
Make sense?
A lot of the complains I hear are based upon false information and
assumptions. Lets talk about some of these.
I’ve had people tell
me that all of these requirements are non-sense. They don’t apply to
Massachusetts. It’s the insurance companies out to limit their
liabilities, or window manufacturer’s wanting to make more money, or
the metal connector companies just being greedy.
I’ve had
people tell me that we have older homes that weren’t built by this code
and they’ve survived all of the hurricanes. There are homes that are
built on field stone foundations without any anchor bolts and they’ve
never “blown away”. Whereas there is truth in these statements they can also be
misleading. Here’s why:
Look at the actual construction of
these older homes. They were built out of old growth forests, which
means the wood was denser and heavier, interior rooms were smaller
(meaning more interior walls providing shear resistance), exterior walls were balloon framed with
continuous studs from foundation to roof, walls were covered with lath
and plaster giving more weight and shear resistance to walls. Today we
built out of light weight woods similar to balsa wood, everyone wants
open floor plans with few interior walls, we build with platform
construction (one floor stacked on top of another, think of a house of
cards), we use drywall board instead of lath and plaster. We don’t use
the same building techniques or materials that the older homes were
built with. So its difficult to compare the two on equal terms. The
homes today are lighter and weaker than the older homes. So the only
way to build homes of today to be as strong as the older homes is
through proper designing and proper materials, including metal
connectors, or we go back in time and build homes exactly like the
older ones. Wonder how many of us would want to do that?
I’ve had people tell me you have to use all of
these metal connectors to build under today’s code. It's like building
with an Erector set. This is not true. We do need some metal
connectors, but plywood and nails if used properly can accomplish many
of the connections we need in a structurally sound home. Again it’s
knowledge in materials and their proper usage.
I’ve had people
tell me we have to use hurricane glass in our windows. Again this is not
true. The building code states that if within one-mile of the mean high
water line of the ocean, and if within a 110-mph wind zone exterior
wall openings must be protected. This is called the Wind Borne Debris Zone. We can accomplish this by one of three
methods as required by the Code:
1. hurricane resistant glass
2. plywood panels
3. approved shuttering systems
Of course you may want to use hurricane resistant glass for the second floor windows instead of being up on a ladder with a large sail (plywood panel) in high winds (of course we always wait to the last minute in case the storm misses us).
The
people that complain about the insurance companies causing all of this
must remember one point, “they don’t write insurance within the coastal
areas anymore” so they aren't limiting their liabilities with the new
code. Window manufacturer’s would rather produce a “cheaper” window not
a more expressive one, because cheaper sells more. And the metal
connector companies have always made metal connectors that were used in
other parts of the country.
So its not the insurance companies
fault, nor the window manufacturers, nor the metal connector makers.
Its because of the way we build and the materials that we use. Its
because of structural failure of homes in other parts of the country
during storm events. Its from wanting to protect people and their
families during a storm, not having a home collapse on them that have
led to these changes. As Bob Dylan once said, “the times they are a
changin’.”
I must admit it seems there is a lot of confusion
out there on the high wind requirements. This is why designers must
detail the proper construction methods needed to comply with these
building codes. It’s why builders must follow the designers’ drawings.
Recently I had a project that the construction of the required shear
walls was properly detailed for the builder, every nail size called for
and where they needed to go.How to block the panel and the size of
plywood to use. However he failed to follow the detail and did his framing the same
way he had always framed. Needless to say this project “failed”
inspection by the local building official and the builder was required
to “tear apart” his work and redo it to comply with the code.
Unfortunately education costs money, whether in college or the school
of hard knocks.
People never like change. Trust me, I didn’t
like having to change the way I design homes. But we can learn and
adapt to the change, or we can get left behind. Massachusetts is the
last coastal state to adopt the high wind codes. Most of our neighbors
have been doing this the past four or five years. Like all new things
there is a learning curve. In a few years we’ll look back on this an
laugh at the challenges we’re going through now. Notice I said "in a
few years."
What if I have a question?
If you have a particular question regarding the high wind provisions of the Massachusetts State Building Code you may submit your question(s) on our Contact Us page and we'll do our best to answer your question (with our opinion) as soon as possible. Please remember it is the local building official's opinion that counts as he is the authority having jurisdiction.
If you'd be interested in attending a training course on these requirements please Contact Us and let us know. If there is enough interest we'll be glad to put together a training course.
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