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Exterior Door Protection
Door Evaluation
The Florida Division of Emergency Management offers a short checklist of items for consideration when evaluating the performance of an exterior door during a hurricane. They are:
- The strength of the door itself must be considered in respect to its ratings of impact resistance against wind borne debris.
- Determine if the anchorage of the door is adequate. This includes the hinges, the lockset and the deadbolt.
- Evaluate the door frame itself. Specifically, determine if the door frame is sufficiently anchored to the house frame so that hurricane force winds will not easily separate the two.
- Consider the door’s ability to seal against potential water intrusion.
Discussion on the section for window opening protection included the devastating results from a broken window with respect to interior pressurization and water intrusion of the house. A door generally covers a larger area than a window. When a door fails, the damage may be substantially greater.
The Florida Division of Emergency Management offers some additional tips for evaluating the strength of an exterior door. These include:
- Look for labels or stickers indicating the door’s ratings for wind pressure and debris impact
- Beware of wood doors with raised panels that are mounted in wood frames. These are rarely rated for wind pressures or impact resistance.
- Just because it is a metal door does not necessarily mean it is designed strong enough. Metal doors are often mounted in wood frames and have hollow form cores.
- Shutters on exterior doors often allow enough leakage around door so that the door still bursts open. This occurred many times during Hurricane Charley.
(See images below)
source: FL Division of Emergency Management
In summary, the Department offers this comprehensive checklist for evaluation of exterior door opening protection:
- 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 the lock edge of the door toward the hinges, does the frame (jamb) move 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 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 ½" 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 in excess of 800 pounds.
- Does the door have raised panels such that when you look at them carefully they are less than ½" 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.
Strengthening a Door
According to PATH (Partnership for Advancing Technology in Housing ), one of the key hurricane retrofits that can be done to existing structures is strengthening exterior doors. They explain that failure of one or all of the following may cause an exterior door to fail in the event of a hurricane:
When there is a failure, the result will usually be a blow in.
PATH’s suggested solutions include:
- Install a deadbolt which penetrates well into the stud framing of the house. Many locks or deadbolts only penetrate into the doorjamb and this is not sufficient to withhold hurricane force winds.
- Improve hinge strength by replacing hinge screws with longer screws that penetrate well into the stud frame.
- Install additional head and foot bolt locks at the top and bottom of the door. If the door is a double, this is considered a must retrofit. Again, the bolts must penetrate into the framing members, not just the trim or surface floors.
Anchoring Doors
To make doors stronger, consider the forces that the door may be subjected to in a storm. Also consider that a door usually opens inward, making it more susceptible to forced wind damage. To give a perspective on the forces being applied to a door, consider the following scenario provided by the Florida Division of Emergency Management:
- The wind force on a 36 inch door in a 130 mph wind (category 3 hurricane) is approximately 580 pounds of pressure.
- For a 150 mph wind, the pressure increases to 780 pounds.
- Hurricanes do not produce nice smooth steady winds but rather winds that are pounding winds which shake and tear things apart.
- Now visualize these effects 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.
- How safe do you feel now?
The Department also offers the following to aid in strengthening an exterior door:
source: FL Division of Emergency Management |
- Structural stud framing for a door opening is almost always much stronger than the door frame itself. For this reason, the door frame and door hinges must be anchored to the structural frame (whether wood or masonry).
- Doors are held in place by locksets and hinges. If only two hinges exist, the door will fail. Three hinges are a minimal requirement.
- Fasteners for hinges must extend through the door frame and shimmed spaces into the structural frame wall. This usually requires a fastener to be at least 3” long.
- Deadbolts must exist and should penetrate into the structural frame wall. Usually this means that the deadbolt be at least 1” long.
- Wood frames are susceptible to being blown in during a high wind storm.
- Glass doors, unless impact resistant, will need to be shuttered.
- If double entry doors, add additional dead bolts top and bottom.
- Install rated doors per manufacturer’s instructions.
- Minimum recommended fasteners: #12 wood screws, 12 penny nails, 3/16” tapcons.
- Spacing of fasteners attaching door frame to the structural frame should begin 6” from end and be spaced a minimum of 16” apart.
According to the publication “Against the Wind” by FEMA, the walls doors and windows make up the exterior shell of the house. When any part of that shell is broken, two major categories of damage will probably occur. First, air will enter the shell, pressurize the house and potential structural failure will occur. Secondly, and probably more likely, water intrusion will damage the interior and contents. Strengthening the windows and doors ultimately strengthens the shell and protects the home.
Management Agency (FEMA) |
The publication also discusses proper strengthening of any exterior double door systems. FEMA’s assessment of the fact that most deadbolts are not strong enough (or deep enough into the doorjamb) agrees with PATH’s discussion above. Additionally, FEMA suggests that there are door manufacturers which provide reinforcing kits to specifically address this problem. Their opinion is that these are inexpensive and easy to install.
source: Federal Emergency
source: FL Division of Emergency Management |
Shuttering a Door
Single or double doors with glass will need additional protection for the glass. This can be accomplished in much the same way that windows are protected. If the door is not impact resistant, an approved shuttering system is the suggested alternative. For more information on both impact resistance and shutters, see the section on Window Protection in this course.
Fixing the Leaks
Another consideration in making repairs to a door, or even in a retrofit of the door, are the gaps where potential water intrusion may take place. After all, more economic damage is done by water intrusion than by structural failure. The Florida Division of Emergency Management offers the following scenario to explain the impact of water intrusion during a hurricane event:
- The gap between the frame of a door and the door can be made to be pretty air tight under normal conditions. Hurricanes are not normal conditions.
- A 3’ wide x 6’-8” door has a perimeter of 19’-4”. If a crack around the door is 1/32” (a few sheets of paper), the total area of cracks would equal a 3” diameter hole.
- Imagine a hose put to that 3” hole with water pouring into the house.
- This is the same effect a hurricane may have on a door.
The Department suggests that weather stripping be checked and replaced as necessary to combat this potential infiltration of water.
FEMA (Federal Emergency Management Agency) offers some weather strip improvement ideas through their publication entitled "Homebuilder's Guide to Coastal Construction". Below are diagrams shown in in that publication:
Replacing Doors
Another solution, and probably the best one, is to replace a non-rated or weak door. This may not be the most economically viable option, but it will yield the best results in the event of a strong storm. Installing a new wind and impact resistant door will also offer the additional advantage of leak resistance as most new doors are designed with better seals.
The Florida Department of Emergency Management suggests that prior to purchase and installation, the door should be checked that it meets criteria for wind pressures and debris resistance. These standards are:
Florida Building Code:
• TAS 201 Large and Small Missile Test Standards
• TAS 202 Uniform Structural Load Standards
• TAS 203 Uniform Cyclic Pressure Test Standards
ASTM (American Society Testing Materials)
• ASTM E 1886 Standard Test Method for Performance of Exterior Windows, Curtain Walls, Doors, and Storm Shutters Impacted by Missile(s)
• ASTM E 1996 Standard Specification for Performance of Exterior Windows, Curtain Walls, Doors and Storm Shutters Impacted by Windborne Debris in Hurricanes.
Southern Building Code Congress International
• SBCCI Test Standard for Determining Impact Resistance From Windborne Debris SSTD-12-97 (Note: This Test Standard will no longer be accepted beginning January 1, 2008)
When using an impact resistant product for a retrofit, it should have passed one or more of these standard tests and have a certificate indicating such.
Summary
The Florida Department of Emergency Management finalizes their discussion by indicating there are 3 ways to protect exterior door openings.
- Repair, strengthen, re-anchor the door.
- Install shutters.
- Replace the door with a rated door.
The Department emphasizes, however, that the best way to combat hurricane force winds is to retrofit the house with pressure and debris rated doors. Additionally, they remind the homeowner that installation should include adequate anchoring of the frame, locks and hinges.
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