2 BUILDING PROTECTION
This chapter focuses on strategies that strengthen housing facilities from natural hazards like wind and seismic risk.
STRATEGIES TO REDUCE BUILDING VULNERABILITY TO NATURAL HAZARDS
FEMA found that 357,492 homes were damaged to some degree by Hurricane Maria, which comprises approximately 23% of the island’s housing stock. Damage is categorized from “affected” to “destroyed.” Even “minor damage” means that people may need to move out, and a home with “major damage” is unsafe to live in, possibly for months or even longer.
For retrofits as well as new construction, investing in mitigation measures before the next natural disaster can protect lives, reduce operating costs on an ongoing basis, save money on repair and rebuilding, and lessen the odds that relocation will be necessary. In 2017, the National Institute of Building Sciences (NIBS) estimated that every $1 invested in mitigation saves $4 in recovery costs for single buildings; mitigation at the community level saves $6 for every $1 spent. Upholding codes and standards are a key to achieving these returns, and Puerto Rico now requires compliance with the International Code Council’s 2018 International Codes.
Each home has particular vulnerabilities based on its structure as well as its site. This chapter explains how to assess and identify building elements that benefit most from mitigation measures. Understanding what makes the foundation, walls, and roof of your home strong, and how to anchor openings and evaluate floodproofing options that can help you devise an overall approach to protect your home while addressing multiple hazards at once.
The foundation, the structural system beneath the walls and roof, the envelope (the walls, roof, windows, doors, and everything else that separates inside from outside), and the mechanical systems are tied together in a “continuous load path,” which acts like a chain that holds building elements together. Maintaining a continuous load path means no single element must bear the forces of the event by itself. This is the key principle in ensuring that housing can withstand threats that originate above ground, such as a cyclone, or below, such as an earthquake.
Protection Glossary of Terms
- Anchor bolts: a bolt is a fastener that is usually used with a nut, for connecting two or more parts. The anchor bolts are usually placed inside the concrete mix before hardening, in a way that the threaded part of the bolt remains outside where an element will be connected to it. Anchoring bolts can be used to connect the wood sill plates of a wood frame. Anchor bolts, in combination with an expansion, can be used after the concrete has hardened by making a drill hole; the expansion will anchor the bolt to the hole in the concrete.
- Metal ties: steel elements that substitute the use of nails directly into wood to connect them. These steel elements are placed over two or more pieces of wood to be united and are then fastened using screws, bolts, or nails, as specified. Tie-downs come in different shapes and are used for different purposes in home construction.
- Fasteners: all kinds of mechanical elements used to join elements, like timbers of steel columns, and that can later be removed. Nails, screws, and bolts are examples of fasteners.
As hurricanes gain strength, structures must be able to withstand greater wind force.
There are four ways in which wind can affect your home’s structure:
- Uplift (wind flows over the roof of the home that create a lifting effect).
- Racking (wind exerts horizontal pressure that can cause the home to tilt).
- Sliding (wind exerts horizontal pressure which can cause home to slide off its foundation).
- Overturning (when the home is unable to rack or slide, wind can cause the walls to rotate off the foundation).