Keeping a house together in a hurricane requires a continuous load path from the roof to the foundation - think about it as trying to keep all the parts of the house connected if you turned the house upside down and shook it.
Each home has its own features and vulnerabilities. This tends to make it difficult to prescribe a one-size-fits-all set of recommendations for retrofits, particularly structural retrofits. Bringing the structure all the way up to the latest high wind requirements could likely mean you’d have to virtually rebuild your house. That is neither cost effective nor practical unless you are rebuilding after a hurricane that essentially gutted your home.
With structural retrofits it is smart to work from the top of the walls downward as each retrofit will engage more and more of the weight of the house. The parts of a house do have a way of working together to help each other out when they are properly connected. By starting at the top, each retrofit you accomplish will make a difference, increasing the ability of your home to withstand a hurricane.
As you take a fresh look at your home’s deficiencies remember what your home might have to face. Wind-resistant homes are not only built to hold up their roofs but to also hold the roofs down. Uplift pressures on a roof in a strong hurricane can be four to five times the weight of the roof. On some areas, the uplift load can be 10 to 15 times that. At the same time the wind is trying to rip the roof off your house, it’s also maneuvering to tip it over, slide it sideways and suck the side walls away. Consequently, the walls and roof have to be tied together like a well-built box and anchored to the ground with enough force to keep it in place. With all this going on, think about what happens if windows and doors collapse. This allows pressures to push off the roof and push out the walls.
Garages with narrow walls on either side of the garage door have little structure in that wall to resist wind forces acting on the side walls
When you consider building or retrofitting here is a good way to visualize what’s needed. Think in terms of how you would connect the roof if you intended to flip the house over and shake it up and down. Hurricane straps are used to anchor the roof trusses or rafters to the tops of the walls. However, it is not enough to just connect the roof to the tops of the walls. The uplift loads have to be carried far enough down into the house so that the weight of the house including the floors becomes greater than the uplift forces caused by the wind. This is called developing a continuous load path. Recent storms have shown that roofs anchored using modern wind-resistant connections have not failed.
Before you rebuild or begin a structural retrofit, you should check a number of sources offered on this website.
- Probably the least expensive and easiest guide to follow is the Standard Building Code Congress guide SSTD 10. It’s a free download through the International Code Council website: www.iccsafe.org/cs/standards/is-hrc/SSTD10/index.html.
- Usually the easiest and least intrusive structural retrofit is strengthening a gable end wall. If your house has a gable end, click on Gable End Walls to look at some of the options available for retrofitting this condition.
- If you have wood frame walls (regardless of the type of cladding from vinyl to brick), click on Wood Frame Walls to explore how to assess your wall's strength, connections and possible options for retrofitting.
- If you have masonry walls (concrete block), click on Masonry Walls to explore your retrofitting options.
A word of advice. If what you are considering is time consuming, difficult or expensive you may benefit by having a knowledgeable structural engineer review your project to see what makes the most sense for you and your home.
