Strengthen structure requires bracing vulnerable areas, stiffening walls and roofs, and by connecting structural elements securely to each other and to the foundation. In Florida, it is important to strengthen the home against hurricane force winds. In the Kansas, protection is needed against strong thunderstorm and tornado winds.
A home’s structure can be fortified against hurricane winds strengthened by four upgrades: strengthen roof deck, brace gable end wall, anchor roof, and
continuous load path.
Many a Florida and Kansas roof has been blown off by strong winds. Hurricane force winds exert tons of pressure on roofs. Roof failure has been traced to roof deck material which is too weak and thin, and to inadequate fastening of roof deck to rafters and rafters to sidewalls.
Plywood at least 5/8” thick plywood (which is much stronger than ½’ inch plywood) is recommended to resist strong wind loads. Old-fashioned wood planks are still stronger. OSB (oriented strand board) is not generally recommended for hurricane zones.
If your roof consists of shingles nailed to plywood sheets, a wind inspection may reveal that the plywood sheets are not adequately nailed to your rafters or roof trusses. If so, additional nails and/or longer nails need to be added to reduce the possibility of the plywood being blown off in a hurricane. The foam insulation in a sealed attic can also strenghtens the bond between plywood and rafter or trusses.
The collapse of gable end walls is common during hurricane winds. The flat configuration of the triangular gable wall catches the full force of the wind, amounting to tons of pressure.
Fortunately, it is possible to brace the gable end roof so that it can withstand hurricane force winds. The Institute for Business & Home Safety website has many suggestions about how to accomplish this http://www.disastersafety.org/projects/?id=2326&category=1187.
A strong connection between the roof and side wall can prevent your roof from blowing away in hurricane winds. Often this connection is made only by toe-nailing rafters or truss on to the top plate of the wall.
Hurricane-Resistant Construction Guidebook (Building Media, August 2006
http://www.hurricaneconstruction.net/?q=node/59 Section 7) gives many ideas about how to anchor roof to the side wall. Also, it gives guidance of how to strengthen the side walls by additional bracing and fasteners.
Metal straps and anchors, which are strong themselves, and are securely attached to both the roof and wall, create a strong bond between roof and side wall. Below are a number of examples of these ties.
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