Just as homeowners should take steps to protect windows on their dwellings, they also should take steps to protect entry doors. Doors also can serve as an entry point for rain and other debris blown by winds. A blown-in entry door and/or garage door can create uplift forces strong enough to blow a roof off a house.
Research has shown the protecting both doors and windows can raise the wind speed required to lift a roof off a house by one or two hurricane intensity categories. For instance, if a roof is lost during a Category 2 hurricane because a door on the windward side of the house was blown open, it might take a Category 3 storm to lift the roof if all of the doors and windows remain intact. Entry doors, sliding doors, garage doors and windows can leave a hole large enough to pressurize the house if wind gets through them.
Entry doors
Doors have similar vulnerabilities as windows, especially entry doors that have a lot of glass.
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Door damages include:
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Glass breaks.
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Glass blows out of the frame.
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The door is pushed open (mostly a problem with inward-opening doors).
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The door frame is knocked loose by wind pressure or the impact of flying debris.
Think for a moment about what’s keeping a door closed.
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On one side, are three hinges.
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On the other side, is a latch that retracts when the knob is turned. There also may be a dead bolt.
What can be done to make a door more secure?
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Add deadbolts and sliding latches – top and bottom – and make these latches long enough to go all the way to the studs and threshold.
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Put stronger screws in the door hinges – again, reaching all the way through the frame to the studs. The screws should penentrate the structure of the house at least 1 ¼ inches.
Adding dead bolts, latches and stronger screws will not only keep the door closed, these materials tend to keep the door frame from separating from the wall.
Of course, strong doors also are important. Steel, solid wood and reinforced fiberglass doors come in hurricane-resistant varieties. Decorative doors with raised wood panel inserts often fail. Look for the label indicating hurricane resistance.
Use the Entry Door Checklist (found below) to determine if a door need replacing.
Double Doors and Sliding Glass Doors
For each double door, at least one of the doors should be secured at both the top of the door frame and the floor with sturdy sliding bolts. Most bolts that come with double doors, however, are not strong enough to withstand high winds.
Your local hardware store can help you select the proper bolts. Some door manufacturers provide reinforcing bolt kits made specifically for their doors.
Some homes have sliding glass doors installed for access to the backyard, pool, etc. While these doors may provide a beautiful view, they can expose your home to certain risks. If your house has sliding glass doors that weren’t specifically manufactured for use in high wind areas, winds caused by hurricanes may push these doors inside the house. If this happens, wind-driven rain will be pushed inside the house and, in some instances, doors and windows on the opposite side may be blown out. Furniture and belongings may be ruined by water and there is a possibility any wind entering the house will cause uplift on the roof and blow it off.
Newer sliding glass doors are made of tempered glass, which is about twice as strong as regular glass. But, even tempered glass can be pushed out of its track and be shattered by large debris. The tracks of sliding glass doors have not been designed to hold the doors in place during strong wind episodes.
Shuttering glass doors is perhaps the most effective ways to protect them from flying debris and possibly help reduce water intrusion. Using a non-porous shutter system will also help prevent the house from getting pressurized if a sliding glass door fails during a hurricane. However, because most shutter systems, even those that are considered non-porous in terms of pressurizing your house, allow pressure to build up behind the shutter on the sliding glass door. That pressure can cause the door to pop out or the glass to break. In some cases, the tracks for the doors may not be all that well attached to the walls of the house. You should check inside the framing to check the condition of the screws, the number of screws, length of screws and the distance between the screws.
Lots of shutter products are available for protecting sliding glass doors. If the doors open onto a porch or lanai, installing code approved impact-resistant screen products or accordion shutters around the perimeter may be the most cost effective ways to protect all the openings to that area from flying debris and also reduce water intrusion around the doors. Make sure the roof of the porch is well anchored to the floor slab or foundation.
Follow these steps when inspecting you sliding glass door to determine if it is strong enough to protect you and your belongings:
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Before you check your sliding glass doors, it is a good idea to make a trip to your local home improvement store or building supplier and take a good look at sliding glass doors that have a Design Pressure (DP) rating of 30 or 40. (This means they are rated to resist a pressure of 30 or 40 pounds per square foot.) Pay particular attention to the frames around the glass and to depth and stiffness of the tracks.
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Now, check your sliding glass doors and look at the relative size of the frame around your glass and at the tracks. Are they as hefty as those you saw in the store for the same size sliding glass doors?
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Check the corners of the glass to see if the glass is tempered. If it is tempered, it will be labeled as tempered.
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Look at the bottom track for the door. If you don't trip over the track, it will not keep water out in a hurricane.
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Check the number of screws and maximum spacing between screws holding the track in place - both on the sides and along the top and bottom. Remove one side screw to see the length needed so they reach the wall studs and about 1 1/2 inches beyond.
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Do the doors fit snuggly into the jamb? Is there air space between the door and the jamb? Is it easy to get the door into the right position to lock it?
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Can you see an air gap between doors when they meet in the center? Is there a gap between the overlapping posts if you have more than two doors in the track?
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Does the track of the door have a piece of metal that comes up on the inside (water dam) at least 3 to 4 inches?
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Are the track and the jamb of the doorway caulked together effectively or at all? You may have to clear out debris, dust, cob webs, or mud to determine if the caulk is effective.
Because sliding glass doors typically open into living space, protecting them is an important part of protecting your house.
Design pressures are a numerical value (in pounds per square foot) that defines the structural wind loading capability of a particular product and determines where and how a product may be installed. Design pressure ratings are determined in test laboratories through severe hurricane simulation testing. Design pressures are how window and door products are measured and differentiate products from one another.
Some tests performed to determine if a door is impact or hurricane resistant are:
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AAMA 506-06 Voluntary Specifications for Hurricane Impact and Cycle Testing of Fenestration Products -- Specification, designed to assist specifiers, uses existing ASTM test methods to qualify windows, doors, storefront and curtain wall as "hurricane resistant."
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ASTM E1886-05 Standard Test Method for Performance of Exterior Windows, Curtain Walls, Doors and Impact Protective Systems Impacted by Missile(s) and Exposed to Cyclic Pressure -- Deferentials method used to determine suitability of products for hurricane-prone areas.
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ASTM E1996-06 Standard Specification for Performance of Exterior Windows, Curtain Walls, Doors and Impact Protective Systems Impacted by Windborne Debris in Hurricanes -- Specification for products used in "hurricane-prone" areas.
Audio Clip: What can I do to make my doors more resistant to hurricanes
Sources:
Institute for Business and Home Safety
American Architectural Manufacturers Association
FEMA Against the Wind
Federal Alliance for Safe Homes (FLASH)
Division of Emergency Management
Hurricane Retrofit Guide