Building Solutions for Grenada

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The Builder's Guide

The  magazine is the most trusted source for building  services in Grenada and a must for all potential homeowners to assist them in building better and safer homes. Our experienced editorial team have worked for many years in the construction sector. US$38.95

Built to Withstand Hurricanes

When hurricanes strike the greatest danger to people and property are flying debris, a piece of wood becomes a deadly missile that can slice through walls. Concrete walls are strong enough to withstand flying debris from hurricane force winds, buildings constructed of concrete is much more storm-resistant than of timber or steel according to researchers for the wind engineering research centre at Texas Tech University. The physical geometry of a building affects its aerodynamic properties and how well it can withstand a hurricane, gently sloping roofs or buildings constructed from timber, steel, or concrete have low drag coefficients and can withstand higher wind forces than a square building of the same area. Monolithic domes, which are made of concrete and rebar have proved especially strong, the sturdy concrete construction combined with the dome shape make these innovative structures nearly impervious to tornadoes, hurricanes and earthquakes.

 

With appropriate design and construction techniques the damage to buildings by these forces can be greatly reduced. Over time a variety of methods have been studied and tested (both formally and incidentally by actual hurricanes) that can help a building survive strong winds and storm surge. Planning authority may mandate strict building code of practise in high velocity areas where buildings are likely to withstand a hurricane or storm surge. A most familiar problem for buildings during hurricanes is storm surge, flooding occurs frequently in coastal areas and waves contain a tremendous amount of energy which can literally destroy a building. A beach front structure should be able to withstand the ocean rising 15 or more feet, these structures preferably be built on high ground where possible in order to avoid waves knocking the building down.

 

The choice of building materials can also affect the ability of a building to withstand hurricanes, although it is not always possible to use different materials, if the area is extremely vulnerable to high winds, it is good practice to use the most resistant materials available.

 

Timber

Timber is the most common building material as it is readily available, relatively inexpensive and has a degree of flexibility which can be beneficial in certain high stress situations and can effectively be built to withstand fairly strong wind loads. However, termite and dry rot are frequent problems in timber buildings particularly in warm and humid climates if left untreated. Weakened timber structure are unlikely to withstand strong winds; therefore to combat this certain building codes require the use of pressure-treated timber for all structural elements of the building, which is designed to prevent rot and deterioration.

 

Concrete

Reinforced concrete is a strong, dense material, resistant to fire and if used in a building that is designed appropriately, can withstand the destructive force of very strong winds, thumping waves and even high speed fragments. Concrete used in home construction must be reinforced with steel rebar, while the rebar can rust in wet or humid environments, there are various effective means to retard or prevent rebar corrosion due to moisture. This material is truly sustainable and that includes sustaining a hurricane. If you are preparing to build a new house in a hurricane prone area, you may wonder what construction material is the best for a hurricane resistant house. We are typically referring to the frame (skeleton) of the structure. The decision of what material to use on the house frame is important, including material cost, performance, and ease of construction. Those of you living in a coastal area, the material performance are of particular importance, but other factors must be examined as well. When it comes to performance, there are many benefits to building a house with concrete. Whether it be formed-in-place concrete or concrete masonry, concrete has inherit strength benefits that will naturally resist hurricane force winds.

 

Roof

Wind acting on the roof surfaces of a building can cause negative pressures that are likely to create a lifting force. This is one of the most common ways a building can be destroyed during a storm. Gravity alone may not be sufficient to prevent the roof from lifting, or detaching off the rest of the building. Once this occurs the structure is weakened considerably and the rest of the building is likely to fail as well. To minimize this, the upper structure should be securely anchored through the walls to the foundation; several techniques can be used to securely anchor the roof. Traditionally roof trusses were simply nailed unto the top of the walls, these nails provide little or no actual structural advantage; they're mainly used to hold the trusses in place while the rest of the roof is being built, gravity and friction then ensure the roof stays put. Various products have been developed that can actually anchor the roof to the walls, which should then be anchored to a solid foundation. Metal straps nailed into the wall and wrap over the trusses are one solution, other method include straps made of a special low elongation material, straps have successfully been used with an advantage in that a buildings which may not be constructed to withstand strong wind loading can be quickly and temporarily strapped to the foundation to ensure structural stability.

 

Window & Doors

Hurricane shutters can also provide effective protection, generally windows, doors, and other openings are usually the weakest points in a building and are susceptible to collapse by high wind pressure and gusting debris. Once failure occurs wind pressure builds up inside the building and within an instant may lift the roof off.

It is usually a requirement to install 150 miles per hour tested windows in hurricane prone areas; these windows should have plastic panes, shatter-proof glass or glass with protective membranes (impact glass), the panes have to be firmly attached than normal window panes (possibly even using screws or bolts through the edges of larger panes).

 

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