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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.

  • Careful not to put lipstick on a pig. Something like earthquake or wind resistance is best engineered into the clean sheet design, it doesn't lend itself to a bolt-on afterthought to be put on right before the paint. – Harper - Reinstate Monica May 15 '17 at 17:23
  • You question isn't clear. What about the product description leaves you uncertain? – isherwood May 15 '17 at 17:23
  • isherwood: Can retrofit work be done to the structures so that I can withstand an EF-2 tornado? – International Orange May 15 '17 at 17:57
  • Harper: Maybe what I have is "as good as it gets". ;-) LOL!! BTW, what is a "Clean Sheet Design"? – International Orange May 15 '17 at 18:00
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    Funny and so true: "Keep in mind that building a house up to code does not mean it's the strongest house you can build; it means it is the weakest the law allows." --archive.tcpalm.com/specialty-publications/vero-beach/… – International Orange May 15 '17 at 19:18
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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.

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  • your advice to contact a structural engineer is very good advice. I think the op was considering tie downs for the roof , those walls with the tie down he linked would also be held in place. His problem I think is that the foundation and slab is in - he would need to do some re-working on those components. – Ken May 18 '17 at 23:29
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To get a better understanding of what you need and how to do it here are some links to the Florida Building Codes. You specifically want to look at the Wind resistance components that relate to your specific location - coastal regions and southern regions have higher wind rating requirements. I think the latest code is 170MPH

There are rules when retrofitting a structure where that retrofit cost < 25% of the value (I could be mixing value with percent of the structure) and also more than x% of value.

https://codes.iccsafe.org/public/collections/FL

http://www2.iccsafe.org/states/Florida_Codes/index.htm

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  • Okay, I see the manual "2017 Florida Building Code - Draft". Is this the correct manual? Do I need to pay for the manual in order to download it? – International Orange May 15 '17 at 20:14
  • The Florida Building Codes are difficult to follow and read especially in that little viewing window. And the search feature is not very useful unless maybe you know exactly what you are looking for as a quick reference. Is it possible someone could help me with the translating the FL Building Code? – International Orange May 15 '17 at 20:50
  • @InternationalOrange - you might call a FL county building division and ask them (they might have a hard copy as well) - the chapters you want are 14,15 and 16. I know it is not a scifi-novel. You can purchase a copy I think it is a bit much $150 for a DIY project. Your link has a video, instructions and reps that can answer about their product youtube.com/watch?v=okCn40bOMEg. They might want you to show your drawings on the garage so they can determine uplift pressure or maybe they have a simple formula and tell you what should be sufficient. – Ken May 16 '17 at 22:59
  • People have different kinds of hobbies that they spend their money on to occupy their free time. Some people like to make their own craft beer, others like to drink someone else's craft beer. Some like to hunt, go fishing, and/or camping and spend a lot of money doing it. My hobby just so happens to be construction/building technologies. This is just what I like to do. Purchasing the appropriate material is not a problem while at the same time I want to be strategic with what I purchase. – International Orange May 18 '17 at 20:05
  • it appears that the FL building code is referring me to another document. Page 4 of Chap 16 states: "The connections shall be capable of resisting the horizontal forces specified in Section 1.4.5 of ASCE 7 for walls of structures assigned to Seismic Design Category A and . . . " Seem like I should be looking for this ASCE 7 manual. – International Orange May 18 '17 at 20:53
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Well, knowing nothing about how the structure is built now does not help. This is indeed a place where designed in from scratch is best and least costly. Is the exterior sheathing OSB? Consider putting a layer of plywood over that, perhaps the fiberglass-reinforced plywood for extra resistance to pulling off in the wind, extra impact resistance, and extra shear reinforcement. Plywood on the interior before sheetrock will also make a stronger wall.

Reinforcing the floor joists (your other question) will have almost no impact on wind resistance, though again, sheeting the bottom of the I-joists with plywood will make that structure more resilient, but by the time that matters the roof is already gone.

Aside from tying the roof down, you want it braced heavily - exactly how depends on the roof structure, but your typical truss roof includes plans for "wind bracing" -much required and should already be in place, some may be "optional" and often consist of a bunch of x-bracing (primarily at the ends for short buildings, and at intervals in longer buildings) and some long-ways bracing that make triangles with the x-bracing. Fiberglass-reinforced plywood is commonly seen in the roof sheathing for high wind areas, but I'd guess you already have a roof surface in place, so you have the deck material you have unless you want a lot more expense.

You could easily sink enough money into lipsticking the pig to pay for a reinforced concrete structure that would have "storm shelter" written all over it. Evaluate your options carefully.

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