If the structural soundness of your building is in doubt, you will need to have it inspected by an architect or general contractor. They can determine if it needs major work to fortify it against disasters (hurricane, tornado, earthquake), or day-to-day hazards such as rain penetration, plumbing leaks, and mold. They can also supervise and verify the performance of any needed updates.
Also, if you are designing a new addition, or doing a gut rehab, you will need someone to coordinate the activities of the various construction trades.
The force of hurricane/tornado winds “tries” to lift your house off your foundation. A continuous load path resists the wind uplift forces. One way of visualizing these uplift forces is to imagine that your house is upside down and gravity is trying to tear it from its foundation.
A hurricane or tornado is barreling towards your home. You see it approaching on the satellite map. Is your house prepared?
Your home is considered hurricane- safe if it is built to code, and/or it meets Institute for Business & Home Safety “Hurricane Fortified Gold” standard for building retrofits. Your home is tornado-safe if it meets local code requirements for tornado safety, and has a safe room in the house or nearby. (Note: If local tornado or hurricane codes are inadequate, the Institute for Business & Home Safety “Hurricane Fortified Gold” standard is a good guide to retrofits.)
Safe is a relative term. We all can’t live in concrete dome houses which can ride out any storm! A conventional well-built home can survive the 157 mile-per-hour a winds of a strong F-2 tornado, or the 155 mile-per-hour a winds of a strong Category-4 hurricane. Few homes will survive a strong F-3 tornado, not to mention F-4 or F-5 tornados. This is why safe rooms are imperative in tornado zones. Similarly, few homes can survive a strong Category 5 hurricane with 200 mile-per-hour winds. In these cases, evacuation is the best option.
Local codes and the insurance industry recognize three basic requirements of windstorm survival. The first is a strong structure characterized by a “continuous load path.” The second is protection of home openings: windows, doors (including garage door), and vents. The third is secondary water protection for roof and siding as well as wind-proof siding and roof shingles and tiles.
Continuous Load Path: ‘Continuous load path’ means that your home behaves as a single structural unit which is securely anchored to a strong foundation. Think of a building block bolted to a concrete block. Such a home will transfer horizontal wind forces to the ground rendering them harmless. (Continuous path load also protects a home from earthquakes which are also subject of horizontal forces.)
A continuous load path extends from top to toe: Think of it as a seatbelt for your home. The retrofit of a home for continuous path may include some of the following items:
1) Strengthen foundation. For example, a weak pier foundation will not do.
2) Securely anchor the wood sill plate to the foundation. Strong bolts are often used.
3) Securely anchor the first-story wall to the sill plate.
4) Strongly anchor the second-story wall to the first-story wall.
5) Anchor the roof rafters or trusses to the top-plat e of the exterior wall. Hurricane or tornado clips greatly strengthen a connection which was made only by toe-nailing.
6) Securely attach roof sheathing to rafters of trusses. This may require additional nails, or a foam-based adhesive.
7) Install new roof sheathing if the old does is too thin or weak to meet code.
8 ) Strengthen walls to withstand horizontal shear forces. In many cases, this means installing plywood which is well anchored to the existing wall. (Shuffling a deck of cards or cutting a paper with scissors are examples of shear forces.)
9) Brace gable end of house.
10) Strengthen chimney anchorage.
11) Strengthen anchorage of porches or carport to home.
Wind- and water-proof roof covers and siding: The building industry has developed standards which certify materials for their ability to resist wind and water. Upgrading a house may include some of the following measures.
1) Install a secondary water barrier on sheathing. This might consist of a self-stick bituminous membrane.
2) Install housewrap to prevent penetration of wind-driven rain through exterior walls.
3) Install wind-rated shingles, tiles or other roof cover.
4) Install wind-rated siding.
Opening Protection: During a tornado or hurricane doors, windows, and vents are vulnerable to failure by wind pressure, or by missiles (e.g., air-borne 2-by-4 boards or gravel). The breach of an opening can result in catastrophic damage. This is why doors, windows, and protective shutters are rated for wind-pressure and impact resistance to flying missiles. Typical storm retrofit measures include:
1) Install wind and impact rated plastic covers over doors and windows.
2) Install impact rated shutters over windows which are already wind rated.
3) Install wind and impact rated windows. These window have tough plastic sheets imbedded between two panes of glass. If the window is cracked, the plastic membrane will prevent wind penetration.
4) Replace flimsy aluminum and plastic soffits and gable vents with windproof units.
5) Install impact rated doors, including sliding glass doors.
6) Reinforce existing garage door or install new wind-rated garage door.
7) Remove gravel from your home landscape. This prevents it from peppering your home like buckshot.
8 ) Trim shrubs and trees near your home to reduce risk of damage from falling trunks or branches.
If you live where the tornados and hurricanes roam, you will benefit from having safe room in your home. Safe rooms are designed to shield you from the maximum-level storm which could ever hit your area. In Kansas City, this would be a Category 5 tornado with winds up to 250 miles per hour. In Miami it would be a 200 mile per hour hurricane.
Winds of this magnitude are incredibly powerful, enough to blow away 99.99 percent of buildings. A safe room has to potentially withstand hundreds of tons of wind pressure and wind-borne debris, e.g., two by four boards hurtling 100 miles per hour.
The federal emergency management agency (FEMA) has developed a wind map to guide the design of safe rooms in houses and community shelters. The map shows then greatest possible wind speed which may ever be expected in regions of the country. Very important: In hurricane country the only really safe way to ride out a hurricane is evacuation. However, a safe room can protect valuables such as antique furniture while you are away.
For a tornado safe room, air pressure is a consideration. When a Category 5 tornado passes over, the outside atmospheric pressure may drop 10%. As a result an interior safe room may momentarily have 200 pounds per square foot pushing the walls and ceilings outward. The resulting balloon-like pressure may be 50 or more tons. For a small safe room, the pressure can be believed by means of PVC pipe vents with an opening area of one square foot.
Because of enormous destructive power of tornado winds and flying debris, a sheltered underground safe room, such as a part of a basement or beneath garage, is ideal. Above ground safe rooms require more extensive engineering to anchor them to the ground, and provide a very strong structure including a safe door.
Not all insurance companies are equal with regard for hurricane and tornado safety incentives. The homeowner must shop around. Florida, a great hurricane state, has a My Safe Florida Home program which requires insurance companies to offer lower premiums on homes certified to be hurricane safe. So it is wise to shop around for lower insurance rates after your home retrofit is completed.
Strong earthquakes violently shake buildings from side to side more than a foot and lift them. It is amazing, but true, that old buildings can be strengthened to withstand such strong forces.
For example, there is the case of two side-by-side identical Victorian homes in Santa Cruz, California. One of the homes was strengthened with foundations bolts and plywood shear panels. Unfortunately, there was no time to install structural wood panels on the other before October 17, 1989 – the date of the 7.1 magnitude Loma Prieta earthquake. The unreinforced Victorian came apart in four sections, and cost $260,000 to repair. The whole building had to be jacked up and slid back together on a new foundation. By contrast, the reinforced building suffered only minor damage and cost only $5,000 to repair.
Another story concerns an apartment building located in the heart of the earthquake-damaged portion of Northridge, California. It was built in 1982 for about $1 million; an extra $50,000 was spent on the plywood and hold-downs. At the time, the builder took “heat” for his decision. He covered the entire building with plywood instead of just the corners.
Twelve years later after the 1994 Northridge earthquake, the builder became a hero. While the quake caused $24 billion in damage, his building remained intact and inhabitable. The two adjacent buildings were total losses. The building’s stellar performance during the quake has served to change the design ideas for the whole of Los Angeles http://www.abag.ca.gov/bayarea/.
A building’s “experience” in an earthquake is like a bus passenger’s during a wild bus ride. When the bus accelerates the passenger lurches backward; when it stops he lurches forward. Going around corners he is tossed from side to side.
Like the standing bus passenger’s feet, your home’s foundation rides the earthquake’s motion. The upper part of the building gets tossed around and bent out of shape. The horizontal forces experienced by a building can be as high as 50 to 100% of downwards gravitational force. The question is: How can building be built or retrofitted to ride out the quake without damage?
Like a hurricane, the earthquake’s horizontal motion pushes a weak home off its foundation, pushes it out of plumb, and may even lift it up and topple it over. To resist a strong earthquake, the house has to be strong from top to toe. Typical retrofits include:
1) Upgrade weak pier and loose rock foundations to a strong continuous concrete foundation.
2) Modify structural elements and their connections so that they form a “continuous load path” to carry horizontal earthquake forces down to the foundation.
3) Add extra bolts to strongly connect the concrete foundation to the wooden sill.
4) Install plywood shear walls and/or horizontal blocking. (The sliding of playing cards over one another or tearing of walls under horizontal forces are examples of shear force.)
5) Reinforce connections between building component with strong nails, metal straps and braces.
6) Replace your old masonry chimney with a metal chimney framed by steel studs.
7) Brace attached porches, decks and stairways.
8 ) Replace brick veneer siding with weather tight covering securely anchored to wall.
9) Brace bookshelves, file cabinets, kitchen cabinets, china cabinets, TVs, refrigerators, heavy light fixtures, pictures, mirrors etc. against falling.
10) Brace water heaters and install flexible gas and water pipe connections. This will the keep the water heater from tumbling over and will prevent flooding and fires resulting from pipe ruptures.
11) Install automatic gas valves which will cut off gas to the house, thus preventing fires and explosions.
To summarize: Your earthquake-safe home must be designed or upgraded to behave as a single structural unit which is securely anchored to a strong foundation. (Think of a building block bolted to a concrete block.) Such a home will transfer horizontal earthquake forces to the ground rendering them harmless. These features also protect a home from hurricane and tornado winds.
When is the best time to retrofit your home? The sooner the better. Your never know when an earthquake may strike. However, earthquake proofing is more convenient if you are doing other remodeling such as insulating, replacing siding or adding an addition. If the big one comes, you will be very happy you did. And if it does not, you will enjoy being safe and knowing that your home will be worth more.
Many homes are lost in known wildfire zones when a burning ember perches upon a wood shingle roof. It does not have to be this way!!
There are many ways to give your home a fighting chance to survive a wildfire. These boil down to three strategies: Deny the fire a path to your door; make your home fireproof; and, fight the fire when it comes. Guidance for protecting homes against wildfires is provided by the National Fire Protection Association (publication NFPA 1144) http://dnrc.mt.gov/forestry/Fire/Prevention/documents/WUIrewrite/NFPA1144.pdf.
Fire could approach your home by air jumping from the crowns of trees, or from the ground. Fire is invited into your home by thick ground cover, thick tree cover, woodpiles, and wooden fences, decks, and outbuildings. Leaves and pine needles in gutters are also fire starters. So thinning out ground and tree cover and keeping any flammable objects away from your home is a must. These include propane tanks.
The area within 30 feet of your home needs to most attention in removing flammable material. But the areas between 30 to 200 feet also need brush clearing and tree removal or trimming.
Even if you did all the brush and tree clearing in the world, still embers flying through the air could set your house on fire. So you need to fireproof your home. The highest priority is a “A-rated fireproof roof. Perhaps the ultimate is a standing seam metal roof. These repel sparks and offer no potential point of entry for embers into the home.
Non-flammable siding and doors repel ground fires. Concrete siding and metal doors provide a high level of protection. Double-pane impact windows protect your home against heat and flaming windborne debris. Shutters are also a valuable protection for windows.
Chimney and stove pipe outlets need to be equipped with spark arresters. Metal screens around vents and soffits are essential to prevent entry of embers. Eaves with exposed rafters provide fire entry points. These need to be boxed in by non-flammable material.
Once a fire arrives there may an opportunity to fight it. Firefighters are helped by street accessibility for their trucks and clearly marked street addresses. Sources of fire-fighting water may include well-marked fire hydrants, pools or cisterns. If your electricity fails, an emergency gasoline-powered home water pump can be used to pre-soak your house and landscape, and to put out small fires. A home fire extinguisher and fire-fighting tools are also valuable fire-fighting aids.
Like DwellGreen on Facebook
