Hurricane Retrofit Guide — Understanding the Risks

Hurricane Retrofit Guide - Understanding the Risks

Drywall damaged by water intrusion

(click image for larger version)

Pervasive Water: At nearly the same level of importance as direct wind damage is the issue of water intrusion. Direct wind damage to the structural elements of homes built to high wind standards has been reduced; however it has become clear that just improving the structural integrity of your home is not enough. Wind driven water intrusion can cause catastrophic damage to the walls, ceilings and interiors of homes that leads to major disruption of households. Furthermore, water intrusion can be of particular importance to you as a homeowner because some insurance policies do not cover water intrusion unless it originates from damage to the roof, walls, windows or doors of your home. When wind speeds get above 60 mph, rain water is driven against the exterior of you house with great force. Whenever water builds up on the exterior wall surface and there is lower pressure on the inside of your house, the water can penetrate in large quantities (quarts and gallons) through cracks, holes and gaps in the siding and around windows and doors. When this happens for hours at a time and usually there is no electricity available to dry out homes using air conditioning or dehumidifiers, the resulting damage and mold can be as devastating as wind damage. Water intrusion has recently become recognized as the major issue it really is. While going through this website take note of the water intrusion issues as much as you do the direct wind load related issues.

Protecting your Home: The most important precaution you can take to reduce damage to your home and property is to protect the areas where wind can enter. According to research into hurricane induced damage, it’s important to strengthen the exterior of your house so wind forces and debris impacts do not create large openings and so that wind driven rain does not cause water intrusion. You can do this by protecting and reinforcing these six critical areas:

  • Roof
  • Windows
  • Doors
  • Garage doors
  • Soffits and attic vents
  • Gable ends

A great time to start securing — or retrofitting — your house is now. Don’t wait until a hurricane is threatening before you take action. By taking actions sooner than later you can get things taken care of in a less stressed environment and complete them in a better way than when you are being threatened by an impending hurricane. Combining retrofitting with other maintenance work. home improvement projects or building an addition can reduce the costs of the retrofits. In many cases, your local building code will require that your work conform to certain requirements. And, although you may not need to comply with current code requirements on the rest of your house, this may be a good opportunity to strengthen critical parts or connections. Remember: building codes reflect the lessons we have learned from past catastrophes and represent minimum levels of protection required for all new construction. Contact a design professional (architect or professional engineer) or your local building code official to find out what the requirements are for your home improvement projects.

Roof damage is by far the greatest risk that your home faces when a hurricane strikes. Well over 90 percent of the homes that are damaged in a hurricane suffer damage to the roof and particularly to the roof covering. The second greatest risk is that wind and water will enter your home through damaged or leaky doors and windows. This includes entry doors, sliding glass doors, garage doors and all types of windows. The highest priority should be placed on reinforcing, protecting or replacing double-wide (two car) garage doors (probably the largest and one of the most vulnerable openings), double entry doors such as French doors, and large windows. Failure of the larger units can allow pressures that would have built up on the doors or windows to enter the house and dramatically increase the loading on the roof structure, interior walls and other exterior walls. Consequently, it is generally recommended that you start with protecting the largest doors and windows first and then work your way down to the smaller units.

Leaks: Cracks around windows and doors are areas where large amounts of water can enter your home; even without structural failures. Additional potential leak areas are: gable end attic vents, roof vents and soffit vents, along with even small holes or cracks around dryer, kitchen and bathroom vents or places where pipes and cables stick through the walls. Many homeowners do not know that winds and rain outside the center of the storm can still be strong enough to create a lot of damage to ageing or poorly installed roof coverings and can produce enough water intrusion to create substantial damage and disruption of households.

The issues discussed in the preceding paragraphs are usually the ones that make the greatest difference to the most people’s houses. This is because more people experience high winds and wind driven rain from the edges of the storm than the number who experience the most intense winds near the center of the storm. However, if your goal is to give your home the best chance of surviving the heart of an intense hurricane, then you need to concentrate a good part of your efforts on retrofits that ensure that the parts of the house are well connected together. Generally, homes built under high wind standards developed in the mid 1990’s are much better connected than those built in the 1970’s and 1980’s. If your home is built in an area where these newer standards have not been adopted or it was built before the new standards were adopted, then it is more likely you’ll have roof sheathing lifted off and further suffer catastrophic damage that could endanger anyone inside and dramatically slow your recovery after the storm.

Assessing the Risks

An important part of assessing the hurricane risks you face is to find out the design wind speed for the area where your house is located. Two different scales have been used over the years to define design wind speeds. The latest codes all use gust wind speeds and all wind speeds referred to on this website are gust speeds with an assumed averaging time of 3-seconds. Building codes used in Florida before 2001 used something called a fastest- mile wind speed that has an averaging time of between about 45 and 20 seconds, depending on the wind speed. You can check with your building department to determine what design wind speed was being used when your home was built. If it is a fastest mile speed, add 20 to get close to the wind speeds used in this guide.

Leave a Reply