Article: construction for high wind area
There was a discussion along these lines some weeks ago, but I am too lazy to chase it down to reference it..
From Science News ( http://www.sciencedaily.com/releases/2008/07/080709110842.htm )
Architect Professor Advocates Best-building Practices For High Wind Regions
ScienceDaily (July 13, 2008) — More than ever before, building design and construction can be significantly improved to reduce wind pressures on building surfaces and to help better resist high winds and hurricanes in residential or commercial construction, said NJIT architecture professor Rima Taher, PhD. Taher, who is also a civil/structural engineer, teaches at the New Jersey School of Architecture. Courses taught by her include topics related to wind and earthquakes with guidelines and recommendations for better design and construction in hurricane and earthquake prone areas.FS
“Certain home shapes and roof types can make a big difference,” she said.
She recommends the following for anyone building in high wind regions.
Design buildings with square, hexagonal or even octagonal floor plans. “Such designs reduce wind loads,” she said.
Roofs with multiple slopes such as a four-sloped hip roof perform better under wind forces than gable roofs with two slopes. Gable roofs are common only because they are cheaper to build. Research and testing show that a 30-degree roof slope has the best results, she said.
Wind forces on a roof tend to be uplift. “This explains why roofs blow off during extreme wind events,” she said. To combat uplift, she advises connecting roofs to walls with nails, not staples. Stapled roofs were banned in Florida after Hurricane Andrew.
Aim for strong connections between the structure and foundation. Structural failure is often progressive where the failure of one structural element triggers the failure of another. Connections can be inexpensively strengthened.
Roof overhangs are subject to wind uplift forces which could trigger a roof failure. In the design of the hurricane-resistant home, the length of these overhangs should be limited to about 20 inches.
The design of the researched cyclonic home includes simple systems to reduce the local wind stresses at the roof’s lower edges such as a notched frieze or a horizontal grid. Install the latter at the level of the gutters along the homes’ perimeter.
An elevated structure on an open foundation reduces the risk of damage from flooding and storm-driven water.
Taher also teaches some courses to help prepare architecture graduates for the Architect Registration Exam. She is the author of a new book about structural systems for the exam. Last year her article about the design of low-rise buildings for extreme wind events appeared in the Journal of Architectural Engineering.
Adapted from materials provided by New Jersey Institute of Technology.
Replies
This is old news for folks living in Florida. They do a lot of things different here because of wind loading. Basically you have a continuous structure from the foundation to the roof with uplift ratings about equal to down load rating. You could almost lift the whole house up as a unit if you could get a uniform grip on the roof.
When I got the engineering for a 14' 8x16 poured concrete beam the uplift was only enough smaller than down load that the top pair of rebar was #5 instead of the #7 I have in the intermediate and lower pairs
http://esteroriverheights.com/electrical/addition/14tie_beam_steel.jpg
Another thing I'heard is to have all the doors in the house open out. Typically the front door is big and opens in. During really high winds the pressure on the door can blow it open and then off comes the roof. That sudden pressurization below the roof would certainly change things.
but if a tree fall in front of the door you never get out
"To combat uplift, she advises connecting roofs to walls with nails, not staples."
Looks like the article wasn't proof read very well...
either that or she has never picked up a hammer and helped build a house.You get out of life what you put into it......minus taxes.
Marv
What???? Don't you "toe-staple" your rafters to top plates?????LOL.Scott.Always remember those first immortal words that Adam said to Eve, “You’d better stand back, I don’t know how big this thing’s going to get.”
I've never stapled my toe.........On purpose.
Why is football called football when you don’t use your feet most of the time?