How can I tell how hurricane resistant a Florida house is before I buy it?

Sunday, September 8, 2019

There is no such thing as a “hurricane proof” house. As more Category 4 and 5 hurricanes with gusts up to 200 mph make landfall, the challenge to keep the walls and roof of a house intact under the enormous wind pressures gets more difficult. But “hurricane resistant” with only minor damage is an achievable goal.

    And most of what you need to know about the hurricane-resistance of a house is contained in the Florida Wind Mitigation form that many homeowners have filed with their insurance company for discounts on their windstorm insurance. The form’s offical name is Uniform Mitigation Verficiation Inspection Form OIR-B1-1802.

   Get a copy of it from the seller if you can and, if not, you might consider having your home inspector provide one as part of the home inspection. When you know what to look for, reviewing the form is like a tour of the hurricane-resistant features—or lack of them—of the home. It will also likely get you some discounts on your windstorm insurance after you buy the home. 

    There are seven sections to the form and each covers different hurricane-resistant feature:

1) Building Code - Homes built under the 1994 edition of the South Florida Building Code or the newer Florida Building Code must meet higher wind-resistance standards than previous codes. The 1994 SFBC was a response to the devastation of Hurrican Andrew in 1991 and went into effect on 9/1/1994 for only Dade and Broward Counties. Other counties in Florida continued to use less-strict codes, such as the Southern Standard Building Code, until the state legislature mandated that the Florida Building Code become effective state-wide in 3/1/2002.

    If “A” or “B” is checked it means the home is more storm resistant than if “C” (unknown or does not comply) is checked. “C” is checked in the example below because the home was built in 1995 and not in Dade or Broward.

2) Roof Covering - This section will tell you whether the roof material has Miami-Dade or Florida Building Code approval for hurricane resistance. It will also state when the roof was installed which, with a quick calculation, gives you the age of the roof. As a shingle roof approaches the end of its servicable life of around 20 years it begins to lose the ability to stick to the roof deck in high winds. You want to see that the “A” box is checked. Also, a properly installed metal roof is more wind resistant than shingles will get a better insurance discount on this form.

3) Roof Deck Attachment - Hurricane-resistance of a house is primarily enabled by what the code calls a “continuous load path” from the foundation up to the roof, meaning that each component is solidly connected to the one above and below it so that any hurricane uplift is tranferred through each link all the way down to the foundation without any part coming disconnected. The highest connection is the attachment of the roof sheathing to the trusses or rafters, and the most wind-resistant connection—also the one currently required by FBC—is “C."

4) Roof To Wall Attachment - This is the other important connection of the trusses or roof rafters to the wall. Mid-20th century houses were toe-nailed, which is the weakest connection. “B” thru “D” are progressively stronger connections, and most newer homes are either “B” or “C”.

5) Roof Geometry - A hip roof slopes up on all sides and is by far the most wind-resistant type of roof shape. If the “A” box is checked, you have the best roof type here, but most roofs will be “B” or “C”, either gable roof (slopes on only two sides), combination gable and hip, or flat roof.

6) Secondary Water Resistance (SWR) - This is also called a “sealed roof deck” and is a self-adhering and self-sealing alternative to regular roofing felt underlayment that provides an additional water barrier in case the roof surface is blown off. A foam adhesive barrier can also be applied to the undersurface of the roof sheathing for this discount. “Grace Ice and Water Shield” is one popular brand of this material. Not done too often.

7) Opening Protection - This category is important if the home is in the High Velocity Hurricane Zone (HVHZ) of Florida, which is all of South Florida and along most of both coastlines, but is also a plus in the rest of Florida as areas begin to get storms stronger than their wind-zone rating in the future. The evaluation requires careful examination of the protection of all openings, documentation of manufacturer’s specs, and is rated based on the “weakest” opening. It can be shutters or impact-resistant doors and windows at openings. We are outside of this zone in our area of Florida, but you should pay special attention to it if you are inside the zone, and the “A” check-box for withstanding a 9-lb. Missile is the best one.

    So it’s simple: a house with the best option checked in each of the seven categories in the most hurricane resistant. Also, see our blog post Why did so many concrete block homes collapse in Mexico Beach during Hurricane Michael?   

• • • • • • • • • • • • • • • • • • • • • • • • • • • •

Here’s links to a collection of our blog posts about the "WIND MITIGATION FORM":

 Is a wind mitigation inspection report (OIR-B1-1802) required for homeowners insurance in Florida? 

 Which building permit date is used for the Building Code section of the wind mitigation form? 

 What are the different roof deck attachment discount categories for a wind mitigation inspection?

 What determines the year of a house? 

 What is the difference between a toe nail, clip, single wrap, and double wrap for the wind mitigation form?

 How do I get the hip roof discount for my homeowners windstorm insurance?

 Can I do my own wind mitigation inspection?   

• What’s the difference between a gable and hip roof for my insurance?  

• Why did I get no discounts or only a small discount from my wind mitigation inspection? 

• • • • • • • • • • • • • • • • • • • • • • • • • • • • 

Here’s links to a collection of our blog posts about "HURRICANE RESISTANCE":

How can I inspect my roof for hurricane damage?

Should I buy a house that has hurricane flood damage?

Should I buy a house with hurricane flood damage that has been repaired?

• What can I do right now to prepare my house for a hurricane? 

How can I tell if the concrete block walls of my house have vertical steel and concrete reinforcement?

How much hurricane wind speed can a mobile home survive?  

• What year were mobile homes required to become more storm resistant? 

Can I do my own wind mitigation inspection?  

• What is the wind mitigation inspection for homeowner's insurance? 

What is the best emergency back-up generator for the power outage after a storm? 

Can I run a window air conditioner on a portable generator? 

What are the pros and cons of concrete block versus wood frame construction? 

Is a metal roof for a mobile home approved for HUD Wind Zone 3? 

Why do so many more sinkholes open up after a hurricane? 

Which trees are most likely to fall over on your house in a hurricane? 

What can I do during a hurricane to reduce the possiblity of roof damage?

    Visit our EXTERIOR WALLS AND STRUCTURE page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.

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