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Tiles from surrounding roofs banged up these shutters (click image for larger version)

Risks associated with windows and doors in hurricanes:
Windows and doors are important features of our homes that provide access, egress, light and view. They are installed in openings framed into our walls and consequently are frequently referred to as "openings" in building codes and engineering standards. Few people want to live in the kind of bunker or cave like environments that would be created if we didn't have windows or glass doors. However, when a hurricane strikes, windows and doors can be blown open or broken, allowing wind and water to entre the home. Risks imposed by windows and doors rank right behind those associated with the failure of roof coverings. Preventing the wall openings filled with windows and doors (including sliding glass doors and garage doors) from becoming openings through which wind and water can enter your home is an important part of protecting you home, your belongings, and your roof in a hurricane. the dual threats are wind pressures and wind borne debris. Your home is particularly vulnerable to having unprotected windows being broken by windborne debris if:

• The design wind speed for your area is 130 mph or greater regardless of tree cover or your surroundings


• The design wind speed for your area is 120 mph or greater and you live in an area with moderate tree cover


• You live in a neighborhood with few trees and the design wind speed for your area is 110 mph or greater


• Vulnerability goes up significantly if you have a tile roof or if one or more of your neighbors has a tile roof, a flat roof with gravel ballast or, old shingles that are starting to curl

Failures of windows and doors from wind pressure tends to be most frequent if they are older units that are not pressure rated, the units have been poorly installed in the openings, your home is exposed to the wind by being located near a large open area such as a field, a body of water or a golf course fairway or on the slope or top of a hill or escarpment.

While these risk factors provide a relative measure of risk, when winds become high enough, damage to unprotected windows and doors becomes much more frequent. A study of homes impacted by Hurricane Charlie, conducted by the University of Florida, found that in areas where gust wind speeds exceeded 120 mph, about 33% of the homes with unprotected windows had at least one broken window. A study conducted by the National Association of Home Builders of damage to homes impacted by Hurricane Andrew, where gust wind speeds exceeded 155 mph, found more frequent damage to windows. They found that 64% of the homes with unprotected windows had at least one broken window.

Window or door failures can increase risks of roof failures: Also, if your home is an older home or was built in an area where they have not been following a modern high-wind building code, you may not have hurricane clips or straps holding your roof structure to your walls. If that is the case, window and door protection may make the critical difference between losing your roof and keeping it on. If a large window or door is broken open on the wall facing into the wind, the overall uplift forces that are trying to lift the roof off your house may be doubled. Research has shown that protecting the windows and doors can raise the wind speed required to lift your roof off your house by one to two hurricane intensity categories. In other words, if it is likely that the roof of your home would lift off during a Category 2 hurricane if a large window broke open on the windward side of your house, it might take a Category 3 or possibly even a Category 4 storm to lift the roof off if all of the windows and doors are protected.

Installing shutters over windows and doors can protect them from the impacts of windborne debris and can keep wind pressures from building up in your house to the point where it significantly increases the uplift forces on the roof. However, it probably won't keep the doors and windows from bursting open from wind pressure if they are weak or poorly anchored to the walls of the house.

Risks of water intrusion around windows and doors: Joe Lstiburek of Building Science Corporation likes to point out that there are only two types of windows and doors, "Those that leak and those that are going to leak." This comment actually contains a tremendous amount of truth since the test standards for water intrusion are set at a very small fraction of the design pressure for the window or door. A realistic example is that if the window or door you have in your home is rated for 50 pounds per square foot of wind pressure (a pressure you might expect from a storm with wind gusts approaching 140 mph) it only has to resist a pressure of 7.5 pounds per square foot without leaking (a pressure that might occur when wind gusts reach about 55 mph) to pass the water intrusion test standard. Since windows and doors are going to leak, he makes the point that the key is to minimize or manage the water intrusion. Keeping water from being driven against and building up on windows and doors is one way to try and minimize the water intrusion during a hurricane. Fixed glass window systems (windows that are not operable) with impact resistant glass that is mounted into the frames with structural adhesives is another approach.

Windows

The primary ways windows fail in hurricanes are:

• Broken glass from wind pressure or more likely from debris blowing around the yard


• Whole windows, frames and all, being blown into houses


• Water coming through the joints of windows or leaking around the frames and into wall cavities

Broken Window Glass

Note all of the small debris on the windows in addition to the broken window - when a window is broken, the water and debris gets blown into your house. (click image for larger version)

The consequences of broken windows: Windows that get broken by debris will let a huge amount of water and strong winds into your house. A house exposed to hurricane Charley had a bedroom window that measured 3' by 3' broken by a shingle from a nearby house. The wall opposite the window was completely wet from floor to ceiling and there was grass debris plastered on that same area. You can imagine how much water entered that room and flowed into other rooms ruining carpets, bedding, furniture, clothing, and drywall. If that house had not gotten dried out within the next day or so, the repairs would have been extensive and the house would likely have been uninhabitable for some time because of mold and odors and then the subsequent repairs. This is not an isolated incident. It makes it quite clear that protecting windows from getting broken is extremely important. Historically and especially before the days of air conditions, windows let light in and kept most of the cold out. If they leaked a little air that was fine except in the winter. The strength of window units and window glass was barely a consideration. Frames were flimsy, glass thin, and air seals not very good.

Wind pressures resistance of windows: Most windows installed before 1996 in coastal areas were not rated for wind pressures and will not do a very good job standing up the wind pressures generated by a strong hurricane. In recent years some manufacturers have begun installing stickers on window frames that provide the pressure rating of the windows. If you can find such a sticker and the pressure ratings are more than 40 to 50 pounds per square foot, you can have some confidence that your home has well built windows that have a chance of resisting hurricane wind pressures. If you don’t find a sticker but know the manufacturer of the windows and the year they were installed, you may be able to track down the pressure ratings. Otherwise you should assume that the windows will probably not do very well in a strong hurricane and plan or retrofit accordingly.

What you should do about windows: When you live in a hurricane prone region and face the kinds of risk factors listed at the top of this page, you should seriously consider ensuring that your windows can resist both the expected wind pressures and impact of windborne debris or you should protect them with a protective system (see the Shutter section for ideas) and is both pressure and impact rated.

Incentives for protecting windows: If you protect all of your openings – that is all windows, entry doors, sliding glass doors, skylights, and garage doors, in the State of Florida, you will qualify for an insurance discount. If you install pressure or pressure and impact rated windows that are also energy efficient, you will get two benefits. New windows can be substantially more energy efficient because they are more air tight and more importantly for most windows they can have glass that reflects the heat from the sun whether sunlight shines directly on windows (say east and west facing windows) or whether the light is indirect (north or south). Direct and indirect heat gain can be substantial so not letting it in will save air conditioning dollars. Sometimes new windows allow one to use a smaller air conditioner when it has to be replaced thus saving money every year.

Keeping a Window in Place

Wind forces on window assemblies: Three common problems in older homes are that the glass is not mounted into its sash well enough to resist wind pressure, that the sash doesn’t stay in, and that window frames are frequently not well enough attached to the house to withstand very strong winds. A 50 mph wind only pushes on a window or door with about 5 to 7 pounds of force per square foot of area, whereas a 100 mph wind applies 20 to 28 pounds per square foot, and a 130 mph wind applies 34 to 47 pounds per square foot. These forces are applied on every square foot of a window. This means that a bedroom window that is say 3' wide by 5' long, when subjected to a 100 mph wind, has between 300 to 420 pounds of force applied to the window and the frame. Think about having 2 men or 3 women sitting on the window. Most windows simply are not designed for those kinds of weights and traditionally have not been installed to withstand them either. The good news is that most window frames lend themselves to being more securely attached to a house.

Poorly attached frames can break loose in high winds - this one was pushed out to relieve internal pressures. (click image for larger version) This window and frame was pushed in by the wind. (click image for larger version)

Unless a shutter is pretty well sealed to the house, it will not significantly reduce the wind pressures on the window. Research has shown that is doesn't take much of an air gap around the edges of the shutters for pressures on the outside of the shutter or wall next to the shutter to be applied to the window. At even the highest wind speeds in a hurricane, air is basically incompressible (you have to get close to the speed of sound before you compress air vary much) so unless the windows are very leaky, it will not take much air flow into the space behind the shutter before the pressure builds up on the window. Consequently, you should stay away from windows even if they are shuttered and if you notice that windows are starting to bow inward because of wind pressure, get out of the room - do not try to help by pushing back on the windows! Broken glass blowing onto you can be fatal. It is like knives or razor blades blowing around.

Strengthening the installation of windows in frame walls: Screws or nails can be installed through the jamb of the window and if the screws are long enough they can penetrate the house framing well enough to provide good anchorage. Bear in mind that screws have to be long enough to get a bite into the framing of the building after they have penetrated the spacing gap that has traditionally been left between the window and the wall so that the window could be shimmed to make it vertical even if the framing is not quite perfect. A gap of 1/2" to 1" on each side is pretty typical. When you tighten the screw, be sure you do not distort the window frame (jamb) because the distortion could let more water in between the frame and the sash, and might prevent the window from operating properly or smoothly.

Strengthening the installation of windows in block walls: Tapcons can be installed through the jamb of the window. They have to be long enough to penetrate the jamb of the window, the shim space, and perhaps a 3/4" think wood buck strip, plus get a 1 1/2" bite into the masonry wall. Be sure the head of the Tapcon does not interfere with the operation of the window. A bevel head may be best. Note that you will have to pre-drill a hole for each screw. You can drill through the window jamb and the wood using a normal high-speed drill bit but you will need to drill into the masonry with a masonry drill bit of the correct diameter for the particular Tapcon screw you intend to use. When you tighten the screw, be sure you do not distort the window frame (jamb) because the distortion could let more water in between the frame and the sash, and might prevent the window from operating properly or smoothly.

Screw, nails and Tapcons: The length of the fastener will be determined by the considerations already discussed. Wood screws should be #10. Nails should be 8 or 10 penny. Tapcons can be 3/16" diameter. Finish nails will be the least visually apparent. Counter sinking nails just a little below the surface and then filling the shallow hole with caulk will make them nearly invisible. If you are sure you are getting a good bite into the structure of the house, then space the first fastener within 6" of the end of the jamb (one fastener at the top and one at the bottom of each side) and then no farther apart than 12". When you install fasteners you can probably feel how well they are biting into the building. If they are absolutely loose, you may have to use a longer fastener. If they are just somewhat infirm the wood of the house may be rotted because of water damage or termites. Or the fastener may be missing the structure. This is sometimes the case when the window on a frame house is located near the outside face of the wall. You should discount the value of any existing nails or screws holding the window in place because in the past not much attention was paid to how many or more importantly how far they penetrated into the structure.

Caulk: You can use a good quality caulk such as a urethane caulk to help secure a window. A good bead of caulk around a window that is wedded to the surface of the house and the window can provide a lot of strength and secondarily provide a barrier to water entry. Regular silicone caulks are not recommended. If you use white caulk select one formulated to be UV resistant so it does not turn yellow. The bead of caulk should not be left so the shape is concave because this does not leave the caulk thick enough to be very effective. Further it is likely to crack because of temperature changes. Most of us find it difficult not to make the caulk look pretty by running our finger along the joint, but it does substantially reduce the effectiveness of the caulk. With this said, it can be beneficial to assure adhesion of caulk by pressing it into the two surfaces to form a concave shape. If you do this, you will need to go back and add a continuous bead of caulk to this first layer so that there is enough thickness for the caulk to react to temperature changes without cracking.

Leaks Around Windows

The Risks: You may well have noticed that water has accumulated on windowsills in thunderstorms. The water is probably rain that got blown by the thunderstorm between parts of the window frame (sash) that holds the glass and the overall frame of the window assembly. Because this is such an occasional event, it usually does not do any or much damage to the house other than cause paint to peel. However, windows that are already leaking like this are a disaster waiting to happen in a hurricane when there can be hours and hours of wind driven rain. If the paint around a window is blistered, especially on the lower end of the window, then the window may be quite prone to let a lot of water in the house if a hurricane blows through.

Ways to reduce leaks around windows: Keeping water from leaking around windows is still a work in progress. All that can be offered at the present time are three ideas that may be worth trying and the recommendation that it is wise to think about water management. The three retrofit ideas are: 1) using opening protection shutters to help keep water off the windows, 2) applying a removable sealant to the outside of the window frame joints, and 3) applying a sticky water resistant tape to the outside of the windows over the frame joints.

Shutters: While opening protection would seem to offer sure fire protection against water intrusion, it is not a guarantee by any means as recent hurricanes experience has shown and evidenced by the two photos below that shows on the window frame and window sill that was covered with silt left by water that was blown past the shutter and through the joints in the window framing. There are indications from water intrusion tests that some of the fabric shutters may seal against the window frame and help reduce water intrusion. Installing shutters some distance from the windows may also help keep water off the windows and window frames.

Both of these windows had roll down shutters in front of them during hurricane Ike that had wind speeds of at most 115 mph. Yet, water came past the shutters and in through the joints of the window where it dribbled down the wall onto the wood flooring. Don’t be confused when viewing these photos by thinking the view is from the outside. It is actually from the inside of cottage type homes that had paneling on inside walls. (click image for larger version)

Sealant: There is a rather unique kind of sealant that can be applied to joints of windows that has the property that it can easily be peeled off without damaging the window. This is true even for painted window frames. This sealant was developed to keep cold air out of houses in cold climates. However, it can work quite well to keep water out. One such product is manufactured by Dap® and is called Seal’n Peel ^TM and aptly described as a Removable Weather Caulk. In hot climates, it is not apt to be stocked in stores; however, it can readily be ordered by stores that stock Dap ­ products. Warning: By sealing windows this way, they will not be able to be opened from the inside while the sealant is still in place. These means that windows that might be used as a means of escape are not available.

Tape: Water resistant tape applied to joints of window frames can be effective as long as the wind pressure is against the window. If a house becomes pressurized because of openings on the opposite side of the house, the tape is apt to come loose so when the wind shifts and blows wind driven rain against the window, its tape will be less effective. To work, the tape must be sticky enough to stay on and must be water resistant enough to maintain its effectiveness. Two types of tape might offer such features. One would be a good quality cloth duct tape. Unfortunately there are a lot of inferior quality duct tapes. Aluminum foil type taped used by AC duct installers is more reliable. The aluminum tape about 2˝" wide has paper applied to the sticky side that one removes when applying the tape. Some brands of this tape have printed instruction for installation. The most important installation hint is to use a semi-rigid squeegee to rub over the tape to press the adhesive to the substrate. When using any tape, the surface must be dust and oil free. Unfortunately nearly all tapes have to be applied to dry surfaces. So plan ahead.

Water Management: In thinking about water management, look around and think about what you would do to reduce damage if you had an inch of flood water on your floor. You would want to get throw rugs off the floor, you would not want wall to wall carpeting, you would want to get anything that could be damage by the water elevated or at least protected from soaking up the water.

Retrofit Measures for Windows that Don't Work: While one might suppose that the simple methods described below would work in ordinary circumstances and conditions, in hurricanes they don’t. These are warnings to the wise.

Tape on the inside: Tape between a window sash and the frame applied on the inside will be almost completely ineffective at keeping water out. The wind will just loosen the tape to let water pass.

Overhangs: One would suppose that windows seemingly protected by having a long roof over them would be safe. They are not. Wind driven rain will drop only about 8” when driven by a 100 mph wind and only about 5” by a 130 mph wind. This makes it clear that overhangs cannot shield windows.

Hurricane rated operable windows: Hurricane rated operable windows, while stronger and more water intrusion resistant than ordinary windows, will still let wind driven rain intrude.

Leaks around windows: The gap between the frame of the window and the sash (movable part of a window assembly) can be made to be pretty air tight under normal conditions. Hurricanes are not normal conditions. In order for a sash to move in the frame over a range of temperatures the manufacture has to provide a gap. Even if the gap is only as large as the thickness of a couple of sheets of paper it can cumulatively result in a much larger area than you might think. For example if a we consider a bedroom egress window sash it is likely on the order of 36" wide by about 36" high so it has a perimeter of 36" times its 4 sides. So the total crack is 72" long. The area of the crack accumulates to be equivalent in area to a square hole with 1 inch sides. In a hurricane this could be like someone standing outside with a garden hose squirting it through your window. You can imagine how much water can come through. So you should not be surprised that in a hurricane a window will allow a lot of water to enter; more water than you can mop up with bath towels. Besides if you are prudent you will not be in that upwind room during a hurricane. Window manufacturers are working on designs that are less likely to leak, but most of the high performance windows currently available are for commercial buildings and cost considerably more, are rarely operable, and look a lot different than windows for homes. Although there are no hard numbers to back up the extra protection against water intrusion afforded by shutters, there is evidence that they can help. This is particularly true if the shutters help keep down the amount of water that builds up on the window and thus is available to be driven through cracks. One row in the shutter matrix gives some preliminary thoughts about how various systems may perform in reducing water intrusion.

Hinged Exterior Doors

Incompletely shuttered entry where not all the door was covered and none of the transom window. Something was better than nothing as long as there was not a false sense of effectiveness. (click image for larger version)

The Risks: Hinged doors are usually large compared to a piece of glass in a window. So if a door gets broken open by wind, unless it is shuttered with a non-porous system, it will almost always result in pressurization of the interior of the home, which then usually causes windows and doors on the downwind side of the house to blown out or roof sheathing to be pushed off. Either of these can be catastrophic to a house, regardless of the structural damage, because of the water intrusion. Furthermore, if the roof is poorly connected to the walls, you could lose the entire roof.

Doors, in the context of this discussion, are assemblies that consist of the door panels, door jambs, locks, hinges, and thresholds. Door jambs are the wood structure immediately around a door panel. The connections of the door jambs to the wall framing are also vital to the performance of the door. The assembly is only as strong as the weakest component.

Door panels are attached to the surrounding jamb by three hinges and one or two latches or locks for a total four locations. According to the `How Many Men’ highlighted box below, a 130 mph wind could impose 580 pounds of pressure on a door. That means that each hinge would have to withstand about 100 pounds and the lock or locks have to withstand 290 pounds. In a 150 mph wind, the hinges have to withstand 130 pounds and the lock or locks have to withstand 390 pounds, the weight of very big man. When wind pressures push against a door that swings out, the door is also restrained by wood of the jamb on three edges (wood stops) and by the threshold at the bottom if the threshold is of the `stop’ style profile, not bumper style. When wind pressure acts in the opposite direction, the negative or pulling direction, that same out-swing door has only the hinges and locks holding it in place. For a door that swings in, the above situation is reversed and the same strengths and weaknesses exist; except that the positive pressure that accompanies wind driven rain pushing against the door will tend to push it away from the stops, opening up gaps through which water will pour. Furthermore, in-swing doors are more likely to burst open when they are impacted by windborne debris because the only things holding them back are the hinges and latches – the wood stops don’t provide any help in this case. The majority of sliding latches that can be added to the lock side of doors are not strong enough or well enough attached to a door or the door casings to offer much additional resistance to wind pressures. Better, stronger, latches are available that can be effective if they have screws long enough to penetrate the wood beside the door. Bear in mind that most molding (door casings) around doors are so thin and so poorly attached that they cannot be counted on to provide much restraint. Screws holding strong slide latches on walls have to be long enough to penetrate through both the casing and drywall, and be well embedded into the wood framing to be effective.

How many men equal the wind pressure on your door? In a 130 mph wind, category 3 hurricane, a typical 3' wide door has about 580 pounds of pressure applied to it. That is more than two heavy men standing, if not jumping, on your door. In a 150 mph wind the 580 pounds becomes 780. That is three 260 pound men standing on your door. Bear in mind hurricane winds are not nice smooth steady winds. Instead, they are pounding winds that shake and tear things apart. Perhaps you can visualize the effects of wind pressures on your exterior door by considering them mounted flat above the floor with the frame on blocks or supported by chairs and men standing or jumping on it. Would you feel safe?

The primary ways that exterior hinged doors fail in hurricanes are:

• The door panel itself fails by buckling or splitting around the lock/latch or bending so much that the lock/latch pulls out of the strike plate; or, the door panel fails from impact of windborne debris.
• A French door or double entry door fails because the connections of the fixed half (top and bottom latches) fail, the two doors bend enough to allow the latch/lock to disengage between the two doors, or one or both of the doors split.
• The door-to-door jamb connections fail because the wood of the jamb cracks or breaks around the strike plate fasteners or hinge attachment points.
• The door jamb-to-wall connections fail because the door jamb was not adequately anchored to the wall framing.
• Water is driven in around the door flooding the floor area behind the door.

The discussion below will help you evaluate your doors for these critical issues. Be sure to evaluate all exterior hinged doors including the side door to the garage. For garage doors for cars see Garage Doors.

Door Panel Failures: If the door is made of metal or fiberglass and there is no glass in the door, the door panel may well resist wind pressures and windborne debris impacts. Some kinds of solid wood doors will also provide good protection from wind pressure and debris impacts. Look on the edge of the door, where the hinges are mounted, for a sticker that indicates the design pressure and impact rating for the door. Beware of doors that have raised flat wood panels installed in a framework of solid wood around the edges. These panels and support members are typically not well attached to each other and the doors frequently burst apart when impacted by debris. Wood panel doors while being aesthetically pleasing can in places have thicknesses as little as a quarter of an inch which is way less than is necessary to resist high winds and windborne debris. Doors with glass inserts, even factory made doors, are at risk of having the glass broken unless the glass and its framing is impact rated. Most doors with glass inserts and nearly all those that were made before 2004 are not likely to be impact rated.

Doors that are not solid wood are usually made by building a frame a few inches wide that goes around the perimeter of the door. Foam or other type filler is used to fill in the remaining space. Then a skin of wood veneer, metal, or fiberglass is applied to both faces. A weakness of nearly all of these doors is the proclivity of the door edges to split where the latches or locks are installed. Entry doors are usually 1-3/4” thick so when they are bored for installation of latches for locksets and deadbolts there is not much wood left. The result is that when wind applies pressure to the door, the edge of the door with the locks does not have much wood left to resist the forces. Compounding the minimal amount of wood remaining at this critical location is the fact that the wood is oriented so that forces on the latch tend to split the grains apart. In fact, it is not unusual to see that wood has been split at these locations because someone or a wind gust closed a door with the latch of the deadbolt protruding. Beware of these kinds of door panels unless they have a sticker indicating that they are pressure and impact rated.

French doors frequently burst open during strong hurricanes. (click image for larger version) Double Entry Door Failures: Double entry or "French doors" have been particularly susceptible to failure from wind pressure. This is largely due to the fact that you have two relatively flexible doors meeting in the middle. While one of the doors has latches that connect into the header and threshold, these connections are usually not strong enough to resist hurricane wind forces. In some cases the latches will pop out of the header and threshold, in other cases, the door may split around these anchors and they will pop out of the anchor holes.

This un-reinforced door frame gave way at the strike plate when the door was subjected to wind pressures. The vinyl sheeting was used to help apply the pressure. (click image for larger version)

Door-to-Door Jamb Connection Failures: Exterior entry doors, and particularly those that open inward, can be forced open by wind pressure or the impact of flying debris. Doors are held to the frame around them by not much - just hinges on one side and the door latch/locks on the other side. Remember that doors can get pulled out as well as get pushed in; but, it is the inward acting forces of the wind accompanied by wind driven water that pose the greatest threat for water intrusion and the impact of windborne debris can impose very high localized forces that can burst a door open into the house. Adding slide latches can add strength to the lock side of the door, but only if the latches are rather substantial, are sizeable, and have long enough screws to hold the latches in place. If a door only has two hinges it probably can't withstand a hurricane wind - Period. Frequently one can see that the wood of the door jamb has been split by the screws holding the strike plate or by abuse. Almost always there is not much wood in the jamb to hold the screws for the strike plate in place. One can purchase deadbolts that are heftier than others. However if the door or door jamb is split or weakened a stronger lock may not offer much additional protection.

In short the failure points at the door jamb are the connections of the door to the jamb at the hinges and at the latches of the locks.

The hinges: All doors should have at least three hinges and a security lock with a dead bolt that is 3/4" to 1" long. Hinges must be well connected to the jamb or better yet to the wall framing behind the jamb. This can be done by replacing the hinge screws with ones 2 ˝” to 3” long.

Latches or Locks: Dead bolts must extend far enough into the strike plate (flat metal on the door jamb that receives the deadbolt and holds the door in the closed position). Importantly the strike plate has to be secured into the jamb really well. Many times that is not the case.

Door Stops: Door stops are integral parts of door jambs against which doors stop against when they are closed. Actually, the door stop may be the same piece of wood as the jamb or it may be an added piece (actually three pieces, 2 sides and top) applied to the jamb. And actually, the door bumps against weather stripping attached to the edge of the stop. Door stops only work in one direction, the direction where the door pushes against them when the door is closed. As pointed out above, the door stop will be most effective in a hurricane when the door is an out-swing door.

Door Jamb to Wall Connection Failures: If field made sidelights or transom windows are present it is highly unlikely the door frame is attached to something that can restrain the high pressures that can be expected to be applied during hurricanes. A strong door and door frame attached to a weak structure is no stronger than the weak structure. Another common cause of weak structure is rotted wood. Wood, studs and jacks, at the sides of doors are commonly found to be somewhat rotted at their bottoms and independently not well attached to the floor structure.

Like windows, the wall framing around door openings is usually larger than the door frame that is going to be installed. This allows the frame to be shimmed so that the door is vertical, even if the framing is not quite vertical. Consequently, fasteners used to hold the door frame in place have to go through the door frame, through the gap and into the wall framing. Fasteners can be added to improve the anchorage of the door frame to the wall. The length of the fastener will need to be at least 3 inches. Wood screws should be #12. Nails should be 10 or 12 penny. Tapcons can be 3/16" diameter. Counter sinking nails just a little below the surface and then filling the shallow hole with caulk will make them nearly invisible. If you are sure you are getting a good bite into the structure of the house, then space the first fastener within 6" of the end of the jamb (one fastener at the top and one at the bottom of each side) and then no farther apart than 16" along the vertical sides and the top. When you install fasteners you can probably feel how well they are biting into the building. If they are absolutely loose, you may have to use a longer fastener. If they are just somewhat infirm the wood of the house may be rotted because of water damage or termites. Or the fastener may be missing the structure. If you are using screws, make sure not to tighten them so much that you warp the door frame.

The door framing and installation details are key elements of a pressure and impact rated door system. To retain that rating, the doors have to be installed according to the manufacturer's installation instructions using the tested hardware.

Evaluating the Risk of Door Jambs: Look for peeling paint at the bottom of the door jamb and the door casing as well as peeling paint on the baseboard. Lock for peeling paint and blistered drywall near the door just above the baseboard. Though termite damage can be hard to see because termites tend to stay below the outer surface of wood and behind paint, one can get hints that there is a problem if one pushes on wood and it gives. In that case one can use an ice pick to attempt to push it into the wood. Where one initially tries the pick it may just happen to hit hard grain (winter grain) so be sure to probe in a couple places. The nice things about using an ice pick is that one gets a tactile feel for the consistency of wood and the cosmetic damage is so small that a little caulk will fill the hole. Termites also eat the paper on drywall where careful examination of drywall may reveal their presence.

A checklist for evaluating door jambs:

1. Look for peeling paint at the bottom of the door jamb, the door casing, and drywall.
2. Look for wood weakened by termites.

The Risks Of Water Intrusion: Out-swinging doors are likely to work better at keeping water out than in-swinging doors because they will tend to push harder against the weather stripping as the wind blows harder. However, no door, except submarine doors, can keep all water out. A 3' wide door with a threshold crack only 1/16" tall is the same as a square hole 1 and 1/8" on a side or a round hole nearly 1 and Ľ" in diameter. Imagine standing outside with a garden hose and squirting water through your door. How much water would come into the house? During the time that hurricanes drive rain against a house, it could be gallons and gallons - much more than you can sop up with towels. And remember hurricanes don't squirt water gently. Do not be mislead by thinking a sweep, piece of rubber or vinyl, at the bottom of a door will keep hurricane wind driven rain out. It won’t because it will just get pushed in by wind.

Click here to download a PDF version of this checklist.

Entry Door Evaluation Checklist  [   ]    Is there no indication on the door that it is pressure or impact rated?  [   ]    Is the edge of the door split where the deadbolt is located?  [   ]    Is the door jamb split at or near the strike plate for the deadbolt?  [   ]    Is the strike plate well anchored to the jamb or are the screws short, loose, or wood split?  [   ]    Is the deadbolt loose or does the deadbolt seem flimsy?  [   ]    Does the door have only two hinges?  [   ]    When you push on the lock edge of the door and push it towards the hinges, do the hinges move the frame (jamb) in a way that does not instill confidence?  [   ]    Does the door jamb seem well secured to the framing of the house? If it obviously is not well secured, you have a problem. But even if it seems well secured then it may take a professional to determine that more definitively. See side bar.  [   ]    Does the threshold seem well attached to the floor? Many times they are not well secured or the anchors/screws work their way loose. It is important that thresholds that have stops (the door bumps into a ledge) be well secured because they will help hold a door in place in one wind direction.  [   ]    If you have double doors with pins at the bottom or top then examine them carefully to determine how effective they are. Are the plates that hold the frames of the pins well secured to the edge of the door? Is the wood around them split? Are the screws secure, long enough, and effective? Do the holes into which the pins are inserted in the threshold and above the door look effective at keeping the doors closed? Do the pins insert at least ˝" into the holes?  [   ]    Does the door have a sidelight?  [   ]    Does the wall around the door seem strong? If a door has `handmade' sidelights, then one needs to be especially concerned about how much strength there is to hold the door and sidelight in place. The forces can easily be excess of 800 pounds.  [   ]    Does the door have raised panels such that when you look at them carefully they are less than ˝" thick in places?  [   ]    Is the door a wind rated door? Is it rated by its manufacturer to be able to withstand pressures in excess of 40 to 50 pounds per square foot? Unless it was manufactured after 1994 it likely is not rated for pressure. If the door is wind rated it will have a label on a side edge or the top edge.  [   ]    Is the door rated to be debris resistant? Unless it was manufactured after 1994 it likely is not rated for impact.

Retrofit Measures for Exterior Hinge Doors

If your answer to any one of the questions above is "yes" then you need to address the issue or just assume the door will fail. There are three approaches to protecting the door opening. One is to attempt to repair the door, another is to install non-porous shutters in front of the door so that the door itself is not such a big issue, and the best solution in many situations is to replace the door with one designed to withstand wind pressures and to resist windborne debris impacts.

Pay special attention to French or double entry doors: Double entry or "French doors" have been particularly susceptible to failure from wind pressure and should have the highest priority for strengthening or shuttering. If you have glass panels in the doors or wood doors with raised panels, your least expensive option will likely be to shutter the door. If they are solid doors, at a minimum you should improve the anchorage of the fixed door by adding heavy duty barrel bolt sliding latches at the top and bottom and make sure the barrels extend into the header and floor (not just the threshold).

Repair the door: There may be ways to repair or strengthen a door installation. Here are some ideas. However, if the door is not pressure or impact rated, you should either replace it or shutter it and then concentrate on reducing the water intrusion possibilities.

• Replacing the screws that secure hinges to the door jamb can add a lot of strength to the fastening. In newer doors typically two screws supplied with the hinges of each hinge are longer than the other two. In older doors this may well not be the case. Even when longer screws are used, they may not be long enough to penetrate the wood jamb of the door, the shim space (which can be as much as 1/2” or more), and get a good bite into the structure of the house. Unfortunately screws typically used for hinges are a little odd in size, being either #7 or #9 depending on the size of the hinge. The screws should penetrate the structure of the house at least 1Ľ" inch. That is they should penetrate the wood frame and the shim space and still penetrate the framing the recommended 1Ľ”. A 2 ˝” or 3” screw is recommended. Replacing a flimsy deadbolt might solve part of the problem on the latch side of the door connection.
• If the door or jamb is split, it may be possible to repair the splits using security hardware available at hardware stores (designed for making door more secure against burglars). A skilled carpenter may be able to salvage a door by the use of suitable glue and some screws. In some situations a metal security plate might solve your door's problems.
• Adding security slide latches can help, but do not be deceived by the effectiveness of ones that use little screws less than ľ" long. When using latches be sure the wood they are being fastened to has the capacity to resist vigorous and repeated tugging.
• Increase the throw of latches or locks. Regular entry locks and some deadbolts are made in two pieces. One is the lockset part and the other is the latch mechanism. If the design of a lock has not changed, then it may well be that a latch with a longer throw can easily be swapped for the existing one.

If the door is split in the lock and deadbolt area, an inexpensive fix may be to install a door edge guard. They are available at home supply stores. They help hold the door together where the latches are installed. In addition, they add more security against break ins.

Door guard wraps the lock side of a door edge (click image for larger version)

If your door has one or more sidelights you need to evaluate whether the wall is strong enough to hold the door in place when the door and the sidelight is subjected to wind forces. It may take a professional to make this evaluation.

Shutter the door opening: Shutters are designed to provide protection against debris, a very important value. However, they may not provide protection against the door being blown open by wind pressure. Also, they may not provide much protection against water intrusion if the panels are not fastened to the house in a water tight manner. If shutters are installed a few feet in front of a door, then they will offer water intrusion protection as well. If they are close to the door, a sizeable impact may damage the door.

This shutter took a direct impact of a large tile missile. The door behind the shutter was damaged as a result. (click image for larger version) The door behind the shutter shown to the left. (click image for larger version)

Replacement: Your best bet my well be to replace the door with an outward swinging door that is specifically designed and rated for high wind and debris applications. Bear in mind a new wind rated door panel is only as good as the weakest element in the assembly that includes the door panel, door frame, the hardware and the attachment to the structure. If you replace a door, make sure that the entire assembly is a pressure and impact rated assembly and that it is installed according to the product approval used to obtain the rating. When replacing a door frame, it is a good time to make sure the screws securing the door to the framing of the house are long enough to hold the door in place in hurricane winds. Such a properly installed door should give you confidence. Getting a new door and getting it installed is not inexpensive, but may be the most cost effective solution. Some doors are simply too hard to effectively repair. Another advantage of a new door is that the weather stripping will likely be better than in an older door. For convenience it is hard to beat a new door because it will always be in place ready to do its storm protection job for you without your having to lift a finger. So with a new door you get better wind storm protection and probably better energy efficiency 24 hours a day. When selecting a door there the two important criteria are the wind pressure rating of the door and whether the door is debris resistant. The design pressure is given as a DP rating for the door. For impact standards, see Local and National Debris Impact Standards. Minimum design pressures in the building code are based on the design wind speed for your location. You can get an estimate of the design wind speed by checking the map in FLAG ASSESS Assessing your Risks. The following table provides values from the building code for doors located near corners of the house. The values will be slightly lower for doors located away from corners (more than about 4-feet away).