In the course of researching hurricane construction over the years I have come across web sites that claim Hurricane Proof homes. Is their really such a thing as a CAT 4 - 5 hurricane or tornado proof home?...Living in Florida for the past 25 years I have heard and read a lot about hurricane construction, Miami-Dade wind code, flood zones, Florida code requirements, wind-mitigation and hurricane preparation. I was also a contractor specializing in residential Hurricane construction and retro fit on the West Coast of Florida so I am familiar with the requirements enforced by our building codes division. I am also a senior property claims adjuster so I have seen the devastation from a hurricane many times over including Katrina and Wilma. No doubt the new Florida Building codes are strict and very thorough in their attempt to provide the homeowner and subsequent homeowners with a structure that is ready for its test against Mother Nature. But bottom line is no home is 100% hurricane or tornado proof. But with the correct hurricane construction features and products you can save your home and contents from a major hurricane with very little damage.
BASIC HURRICANE CONSTRUCTION FEATURES - FOR A NEW HOME
First you have chosen a building lot away from the water if possible.. The foundation or root of the house is planted firmly in the ground with re-bar and footings, including blow outs for flooding, with solid concrete or cement filled exterior walls. The home has continuous hurricane strapping from footing to ridge. You have chosen Miami- Dade code storm ready windows and doors for ALL openings, vents have pre made protective coverings, all doors open out, no double doors, a Miami Dade hurricane coded garage door and a very durable exterior finish for the house, you have also followed the guidelines for roofing and nailing your shingles (not Barrel Tile) down securely to code and used plywood not OSB on the roof deck and walls. You have designed a low sloping roof with no gables and have installed a good moisture barrier system in the attic.. You also removed any large trees or branches from around the home or other structures. And have installed an emergency generator.Following these basic construction elements have proven time and again that your home will weather the storm with much less damage and costly repairs to the house and contents.
fiber-cement sided house in Jackson County, Mississippi which survived Hurricane Katrina.
Hurricane strapping to hold down the roofing system
Retrofitting an older or existing home will provide significantly better hurricane home protection, but the best hurricane resistant homes are specifically designed and built to withstand hurricane force winds. If you're planning on building a home in a hurricane-prone area, it's a great idea to look at construction methods and companies that offer hurricane resistant homes. Not only are these homes superb at withstanding some of the harshest conditions Mother Nature has to offer, but they are also very energy-efficient and fire and pest-resistant. The cost of making a home more wind-resistant is worth the investment...
Contact the local building department and obtain pertinent information on local construction requirements. In particular, the construction requirements should differ between coastal (i.e., beach exposure) and inland homes. Certain construction requirements may vary somewhat from one locality to another, but most critical requirements in hurricane prone areas should be consistent Proximity to the Coast Determines Level and Type of Risk Storm-flooding caused by wind-driven sea water that can wash-out foundations and crumble, is a major concern for coastal homes (i.e., on the beach or barrier islands). Therefore, it is highly recommended that these houses be placed on pilings in accordance with (1) local regulations that may be based on the National Flood Insurance Program (NFIP), (2) FEMA coastal construction manual guidelines, or (3) a design by a qualified design professional. Pilings elevate the living areas of a home above the storm surge height, typically based on an estimated 100-year flood height (including wave height).
For inland homes along the Gulf and Atlantic coastlines, wind is the major risk factor. Wind can cause structural damage, such as blown off roofs. More commonly, it causes the roofing, siding, windows, and other exterior finishes) to be damaged, allowing wind-driven rainwater to enter and damage the contents of the home. Damage may be attributed to any number of causes including the storm magnitude or rarity, minimum code requirements, construction quality, material durability (i.e., corrosion or rot), site exposure, and many other factors.
Your neighborhood and surroundings affect your vulnerability to hurricane damage
Consider All Design Decisions That Reduce Risk From Wind and Water Damage
The advice of an experienced local builder, design professional, or code official is recommended in determining the appropriate design decisions for any home, particularly those in hurricane-prone areas. However, many important issues may not necessarily be addressed specifically in the building code. Therefore, the following may serve as "universal" guidelines for improving a homes ability to resist wind-related damage from hurricanes. Bear in mind that trade-offs must be considered since improved performance generally means more construction cost or sacrifice of certain desirable features. Also, these tips are given with the understanding that the construction must meet your local building code requirements.
Consider living in a less risky environment (not an acceptable solution to those desiring a coastal or beach lifestyle).
A lower profile house is inherently less vulnerable (i.e., a one-story house is less likely to experience wind damage than a two-story house.
A gable roof home is inherently more vulnerable to wind damage than a hip roof home, although this can be overcome by structural design.
Very low and very steep sloped roofs generally create increased uplift and lateral wind loads, respectively, and should be avoided. Always use Plywood on roof deck and walls not OSB.
Ensure that adequate connections, brackets, anchors, or tie-straps are provided to transmit wind uplift loads adequately to the foundation. The need for and amount of special connectors will vary by house configuration, site exposure.
Another good feature is an insulated,reinforced concrete form wall system that meets the wind-load and impact resistance requirements of the South Florida Building Code. Note: cast-in-place concrete walls are stronger than concrete masonry unit block. If using block fill all cavities with cement.
Added steel reinforcing around windows,door openings and sliding glass doors helps keep these units in place during high winds.
Storm surge considerations - Along The Coast
A very common and catastrophic problem for buildings and homes during a Hurricane is storm surge. Flooding occurs frequently in coastal areas and waves contain a tremendous amount of energy which can literally batter a building to pieces. Beach front buildings should be able to withstand the ocean rising 20 or more feet with large waves on top of that. They should preferably be built on high ground where possible in order to avoid waves knocking the building down.
If waves can reach the building site, the building should be elevated on steel, concrete, or wooden pilings and/or anchored to solid rock. Whether it is intended or not, the walls on the first floor are often built with sheetrock which can completely deteriorate when wet and/or exposed to lateral forces, leaving structural members in place, and allowing water (or high winds) to pass through. This "gutting" occurs frequently in storm surge areas. If done by design, "sacrificing" the walls of the first floor is not an ideal solution, although it can save the rest of the building from destruction. Of course, building contents left on that level will be lost and considerable damage to the building could still result in costly repairs such as mold, rot, and termite problems under building materials.
Hurricane resistant home built in Gilchrist,Texas
Florida- Pedestal design elevated 20-ft. Built by TopSider Homes
Palm Harbor Homes
BACK TO THE BASICS FOR THE PRE-EXISTING HOME
Double French Doors that open in provide very little protection against hurricane force wind.
IMPORTANT:Exterior doors should always open outward..An inward opening door can be blown into the house by wind...From my experience time after time this a very common cause for damage to a home with a very simple fix.. All doors should open outwards with no double doors on the exterior of the home, they lack support in the center...Unfortunately and to my amazement most new Florida homes are built with double door entry ways. It is very common that in a middle of a hurricane homeowners nail 2 X 4 's to there exterior doors from the inside tring to keep them from blowing in.
Strengthen exterior doors
Failure of the lock set, doorjamb or hinges frequently causes doors to blow in.
The deadbolt should have a long throw (at least one inch) that should penetrate into the stud framing, not just the doorjamb.
To strengthen the hinge side, ensure at least three hinges are properly installed with the hinge screws penetrating through the doorjamb into the studs.
Installing slide locks (also called head and foot bolts) at the top and bottom of door will further strengthen door. They are absolutely necessary for double doors. Ensure that the locks are mounted securely to the sub floor and door header, not just into the trim.
DOUBLE DOORS Beefed-Up Door Hardware: Some simple hardware changes are all it takes to dramatically improve the strength of a pre-existing non-hurricane coded double entry door. For starters, replace hinge screws with longer versions that extend all the way through the surrounding framing. Change out the standard deadbolt for a longer-throw version, and add dead bolts top and bottom. Multiple-point locking systems, like the Trilennium from W&F Manufacturing (starting around $300), have two or more internal dead bolts, giving you added protection without compromising looks. Finally, add vertical locking pins to the top and bottom of the moveable door; in a traditional setup, only the stationary door has them. Make sure the lower pin extends deep down into concrete or solid wood.
Replace hinge screws and deadbolt locks with longer versions; add multiple-point locking systems and vertical locking pins
impact-resistant windows and doors.
Impact Resistant Doors & Windows Their construction and anchoring systems keep high hurricane wind and debris from breaching your homes outer envelope.
Protecting the Building Envelope Windows and doors offer a significant opportunity for combined wind and water damage in hurricanes, impact-resistant windows and doors can save structures from destruction. A broken window provides a point of entry for wind, that enters the house, increases pressure, and seeks another way out. When a building envelope is breached, the difference in air pressures inside and out will cause a building to lose a roof or a wall and when that happens, the building is totally exposed and structurally compromised.. The only way to protect against damage from wind entry is to keep it out. This means deflecting wind and driving it around the building, making sure all openings into the home are protected.
NOTE : One of the most stringent of the requirements comes from the South Florida Building Code, which has been concerned over the increase in the number and force of hurricanes in recent years. Beginning in July, 2001, the South Florida Building Code required every new home have exterior openings in a house be protected against flying debris either by shutters or impact resistant windows.
A broken window provides a point of entry for wind, that enters the house, increases pressure, and seeks another way out.
Retro-fit Note- Impact-resistant windows and doors are optimal for windows and doors not easily fitted with hurricane shutters or windows that are in hard to reach areas as in 2nd or 3rd stories. Also make sure to install an impact resistant system on sliding glass doors because they are larger and more vulnerable to wind and debris. If your sliding glass doors or windows cannot be replaced with impact-resistant ones, then at the very least install hurricane shutters on ALL openings to the house, including vents.Hurricane coded storm shutters made of steel, aluminum, or high-strength polycarbonate plastic such as General Electric's Lexan are advisable.
The front door and accompanying windows, in addition to the back door and accompanying windows can all be covered by a sliding corrugated aluminum door.
Clear storm panels - Let's the light shine in!
Impact resistant glass - Performs both Beauty and Function
This one story Pine Island, Florida home pictured right was near the eye of Hurricane Charley a Cat 5 , yet was almost undamaged.. The hurricane shutters installed on this home protected the doors and windows. This home also has a very durable metal (key west style) roof not shingles.
Pine Island Florida
Bracing For the Big One! Reinforce gable trusses
Many gable roofs fail because the end wall collapses. Fortunately, reinforcing them is fairly easy.
Observations made in the aftermath of Category 3 and stronger hurricanes have clearly illustrated the vulnerability of gable ends. Failure comes in three varieties: The most common gable-end failure is one where the wall loses support along its top edge — typically because the sheathing gets blown off. The second most common failure is at the connection between the triangular gable-end wall and the rectangular wall below it. In this scenario, the wall gets pulled out by the negative pressure of the wind. The third potential failure is collapse of the actual framing members that make up the gable-end wall structure as a result of bending stresses from positive wind pressures. In any case, the damage is usually disastrous to the home and its contents. Not only is the structural damage severe, but a collapse of the gable-end opens the house to wind-driven rain, which can condemn a home to catastrophic damage.
Hurricane Reinforced Gable Trusse and Roof System
In Florida, the vulnerabilities of gable ends have been recognized as so significant that the legislature mandated that the Florida Building Commission adopt voluntary methods for retrofitting gable ends of homes into its prescriptive building code. The code is available online from the Florida Department of Community Affairs (www.floridabuilding.org/
The 78-page Hurricane Retrofit Guide (www.floridadisaster.org/mitigation/rcmp/hrg/index.asp) devoted to gable-end retrofitting provides ample detail. The length of this guidebook is not a reflection on the difficulty or complexity of this work but rather an indication of the number of construction variations, all of which have been addressed in those pages to save retrofitters from having to scratch their heads to reinvent the wheel. Included are 22 drawings, many photographs and tables, and many helpful hints to guide one through the retrofit process. The document is downloadable as a PDF file so it can be printed in whole or part. In addition to covering gable ends, the Web site addresses many other retrofit measures, including the use of construction adhesive for securing roof and wall decking, attic ventilation considerations, securing gable-end overhangs, and soffits, among others.
Retrofit - Braced Gable
Un-Braced Gable-Negative pressure from hurricane-force winds pulled the top of the gable end outward after it ripped off the sheathing at the edge of the roof. Retrofitting a Home can dramatically reduce the risk of such an occurrence.
Strengthen a gable roof by bracing the end walls, which are the most vulnerable to uplift
. Bracing: Hip roofs, in which all four sides slope toward a central ridgeline, are naturally more wind-resistant than gable roofs. One way to strengthen a gable roof is to brace the end walls, which are the most vulnerable to uplift.
Get up into the attic and nail or screw a pair of 2x4s in an "X" pattern—one extending from the peak of the gable to the bottom center brace of the fourth truss, and the other from the bottom center of the gable to the top center brace of the fourth truss. Use 3-inch-long wood screws with a ½-inch-diameter shank, or 16d galvanized common nails, and reinforce the new braces wherever they meet roof members with 1-inch galvanized-steel straps.
If your roof is framed with rafters, you can strengthen it by adding collar ties. Adding collars will improve a roof's ability to take wind load. Brace every pair of rafters by running a long stud from one side of the roof to the other, three-quarters of the way up the slope of the rafters (imagine the letter "A"). Fasten it at each end with long wood screws and galvanized-steel straps, effectively creating a bridge across the inside of the roof.
Adhesive: Then run a half-inch bead of construction adhesive along each rafter or truss where it meets the plywood roof sheathing above. "A good, thick bead down the edge on both sides of the rafter will tighten everything right up.. This simple step will roughly triple a roof's protection against being torn off by the wind.
Strapping: Hurricane straps—1-inch-wide galvanized-steel ties that extend from the stud to the top plate and over the truss or rafter—tie the roof and walls together. While it's not easy to retrofit them (there's little maneuvering room in the attic at the edge of a pitched roof), it can be done by a skilled professional, who may need to remove a section of roof sheathing or siding to gain access. Attach a strap at each roof-to-wall connection.
Hurricane straps—1-inch-wide galvanized-steel ties that extend from the stud to the top plate and over the truss or rafter—tie the roof and walls together.
Removable bracing system for garage door..."Approximately 80% of residential hurricane wind damage starts with wind entry through garage doors."
Reinforcing THE GARAGE DOOR.
The Danger: If your home has an attached garage, think of that wide, roll-up door as a hurricane welcome mat. When 100-plus-mph winds hit the relatively thin aluminum panels of a standard door, typically, that door buckles and fails, allowing pressure to build up inside the house until it blows apart. See the Garage Door section on this web site.
Permanent Solution:Replace your garage door with Dade County Approved hurricane rated models. That means braced steel construction with beefier rollers, hinges, and tracks, and additional track-attachment points. This is a must do!!
Removable Bracing System: Temporary reinforcing posts will improve your chances against a blow-in or pull-off. A retrofit kit, like the aluminum Collier Fortress Brace or the Secure Door system, sells for about $150 for a standard single door. Vertical posts slot into holes drilled in the floor and fasten at the top via a pre installed bracket. When a storm warning goes out, you simply insert the posts to bolster the door.
A couple of angle brackets could have kept this compressor in place
Anchor Outdoor Equipment: Equipment outdoors or in a carport such as air conditioning compressors, water conditioners, water heaters, pool equipment, washing machines, and the like may well get blown around in a hurricane. While they may not get blown very far, it may be far enough to cause a lot of damage to the equipment. Damage, to electrical hookup and condenser lines, that can be hard to get repaired after a hurricane. People who have had their air conditioners damaged and had to wait first for restoration of electricity and then for a repairman in mid summer heat can testify you don't want this to happen to you. Luckily it is easy to anchor such equipment. Some manufacturers make kits for anchoring their equipment. If not, you may be able to make your own and use the manufacturers own cover screw attachment points to anchor the equipment. All it may take is a few right angle brackets to connect the equipment to a concrete slab, a wood porch, or a wall. There needs to be enough brackets to resist wind forces from all directions from a Cat 1 or 2 storm.
Screen Enclosures Aluminum screen pool enclosures have become quite popular in Florida. Unfortunately, they are often poorly designed to resist wind loads, and inadequately anchored, braced and connected. The building code tends to focus on life safety issues. Since no one is expected to try and ride out a hurricane in a screen enclosure, the code allows designers to design these structures for 23% lower forces than are required for your house. Reviews of enclosure failures suggest that the simplest retrofits that may do some good include improving the anchorage of the columns to the concrete deck and installing additional diagonal bracing. In a lot of cases, the screws begin to rust almost immediately and loose considerable strength. Replacing rusted screws with slightly larger stainless steel screws is another way to try and get the most out of the structure you have in your existing screen enclosure.
Typical anchorage of corner column in older screen enclosures - this is a very weak connection for resisting either uplift or bending
Replacing screws that are backing out, rusted, or broken can help you get what strength you can out of your existing frame
This is a very well made Aluminum Structure BUT: Aluminum structures such as carports and pool enclosures are often inadequately anchored, braced and connected. They are often the first structures to be blown down and then blow into your house and possibly your neighbor's.
Very well made screen enclosure
Trees vs. Wind
Property Damage Caused By Fallen Trees. Trees and shrubs, even those native to an area, can grow too massive or unbalanced to be able to withstand windstorms or hurricanes, removing or trimming these trees in order to minimize the risks of damage to your home or your neighbors home and property is a very good idea. When a tree falls or breaks up it is more likely to damage a structure close to it than one farther away. If the landscape planning includes the use of trees to shade the house, some compromise will be necessary to avoid the shade-tree turning into wreckers during a storm. It is more important to shade the east and west walls than the roof. Small trees or bushes could be planted fairly close to the house to accomplish this, and they would be much less hazardous than larger trees, even if the larger trees were farther away. Observations of native tree hammocks in Dade County suggest that a large number of small trees close together may be an effective storm protection for structures, but no definitive testing of this theory has been carried out. Overhead utility lines are even more vulnerable to damage than the roof or windows of a house, and there should be no tree branches close enough to drop across them or even brush against them. Keep electrical lines clear of tree branches.
Windstorms are always a matter of concern, but trees that have been selected properly, sited with care, and maintained so as to have a sturdy form and an open canopy stand the best chance of surviving intact and not adding to the damage in the area.
WIND RESISTENT TREES
Some tree species are better able to withstand strong winds than others. Wind resistance is especially important when planting or deciding to keep large maturing trees (over 30′), since they have the potential to cause the most damage. Studies of trees surviving hurricanes in Florida and the gulf coast found live oak, southern magnolia, and baldcypress to be the most wind resistant large trees. Other large maturing trees that proved moderately to highly wind resistant in the studies were hickory, persimmon, shumard oak, river birch, and black gum, also known as tupelo
HURRICANE CONTRUCTION VIDEOS LINKS:
The Link below features multi-media demonstrations of innovative hurricane resistant construction techniques and products featured at the LaHouse Resource Center on the LSU campus in Baton Rouge, Louisiana.