I have an unfinished detached two-story garage that is about 20' x 24'. Before I start putting on the make-up and lipstick I want to (if possible) make improvements to the structure beyond the basic building code safety requirements. I believe the current local building code requires 3-second gust at 90 mph.
My goal is to make the structure resistant to an EF-2 tornado (3-second gust 135 mph).
It would seem that by now, "Wind-Resistant Construction" should be more common knowledge and less of a specialty field. New code requirements in Florida and costal communities require and promote more Wind-resilient structures which saves cost to the everyone in the long run.
There is a Simpson Strong-Tie Technical Bulletin titled, "Strengthening Dwellings in Tornado-Prone Areas".
High Wind-Resistant Construction Application Guide
F-C-HWRCAG16 is a 80-page, color application guide discussing the critical elements of high wind-resistant construction and includes information on the effects of wind, corrosion and uplift, and provides detailed product information for construction in high-wind areas.
I did see a Simpson Strong-Tie Strong-Rod uplift Restraint System on page 47 of the catalog. This looks like a doable retrofit if it will meet the EF-2 requirement. Is there a way to determine if these will work for my application?
The Simpson Strong-Tie® Strong-RodTM Uplift Restraint System for roofs
(Strong-Rod URS) is a continuous rod tie down solution designed to
provide a complete load path to resist suction (uplift) pressure on
the roof. After hurricane ties transfer roof uplift forces into the
uppermost top plates in a wood-frame structure, a Strong-Rod URS
continues to transmit that resistance down to the foundation or final
termination point. Visit www.strongtie.com/srs for more information.
Thanks.
Best Answer
Actually, it's not just "tying the roof down to the foundation." Its more than just uplift. It's tying the roof to the walls (for lateral resistance), then tying the walls to the foundation.
Where I live, we get 120-140 mph winds every year, but they're "gusts". Where you live, the winds (tornados...hurricanes) are "sustained" winds. Much tougher to design resistance for hold-downs and lateral resistance.
However, here we have seismic problems...both vertical and horizontal loads. Structural design is a process. I'd contact a structural engineer (not a civil engineer) or an architect.