Your home in a hurricane*

By Kaelanne Jordan, kjordan.camsel@rcpos.org

The ongoing discussion of rethinking infrastructure has circulated recently, particularly since Hurricanes Harvey, Irma and Maria decimated critical infrastructure in the region.

While the idea of a hurricane-proof home may seem like pure fantasy, one architectural firm based in Port of Spain revealed that there are varying extents a homeowner can pursue to limit damage to its structure and keep occupants safe. The challenge faced, however, is how practical or affordable it is, according to architect Stein Carrington at GSAL Designs Limited.

For instance, if both walls and roof were constructed of thick reinforced concrete – a concrete bunker for example – this type of structure will withstand the most severe hurricanes.

On the other hand, this type of structure would also be excessively expensive to build. “Additionally, buildings and homes still require windows and doors, and these can still incur damage during harsh weather conditions. Another reality is extreme flooding; a consequence of hurricanes that can still render a home susceptible to disaster. So this still makes ‘the how?’ difficult,” Carrington said, via email.

What makes a building or structure fail during a hurricane? Kevin Granger, Director, Beston Consulting Limited, a network of civil and structural engineers said it is difficult to design the entire structure to be strong enough to completely resist a hurricane’s forces. Instead, he said, buildings are designed to bend and deform in a predictable way to prevent collapse.

He explained, “Like the electrical system in the home, structural engineers design structural fuses throughout the building to protect it and the occupants. When this ductility is overlooked, buildings perform badly and fail.”

Granger said there are three phases of a building: design, construction and life cycle. Errors, he said, can be made by a contractor if he does not construct in accordance with the drawings produced by the professional and poor workmanship [e.g] “the homeowner may inadvertently alter the building by creating a large opening or adding a floor which affects its design.”

Meanwhile, Carrington said when operating in a “practical realm”, the most integral elements to withstand most natural disasters are a well-designed and stable foundation, vertical supports (walls and columns) and horizontal supports (beams and roof structures).

How well these are connected through its design and construction are vital to being resilient to natural disasters especially hurricanes, he said. “The shape of a roof also affects its performance in a hurricane, gable roofs with low pitches and large overhangs tend to be more susceptible to strong winds,” he said.

Unprotected windows and areas under the roofs are the most vulnerable areas in a hurricane, hence it is critical that homeowners pay attention to width of eaves (shorter eaves provide less area for the upward lift of roofs). In lieu of the eave width, it is important to have roofs anchored well to the top of walls and beams.

The spacing of timber or metal framing members (rafters or purlins) should be specified by professionals, or specialist contractors and the welding or bolting of the members to the wall is vital, Carrington said.

Commenting on this, Granger recommends that homeowners should firstly ensure that their buildings are fully approved by the statutory agencies. In doing so, they will be expected to employ competent personnel for both the design and construction of their homes.

Granger said, “If the home has already been built and the approvals status is unclear, they can have an assessment conducted by an engineer or they can, with limitations of course, inspect their buildings for signs of distress and discontinuities in the load path.”

Buildings exclusively constructed with horizontal core blockwork are more prone to problems than buildings using vertical core blockwork due to reinforcing challenges. Hence, “we do not recommend 4 inch thick blocks for load-bearing purposes. For framed structures, columns should have a minimum dimension of 12 inches, but this should be verified by a professional,” he said.

Carrington’s advice to the homeowner seeking to implement hurricane safety measures into their existing structure is to start with the roof, ensuring eave widths are short and rafters and purlins are well anchored to walls or ring beams. Steeper pitched roofs at approximately 30 degrees tend to perform better in harsh wind conditions, he said.

Construction industry unregulated

 Currently, Trinidad and Tobago does not have a National Building Code or a mandatory Standard that must be used for construction. According to Granger, professional engineers generally use the International Building Codes (IBC) as it is a requirement for approval by the Ministry of Works and Transport’s Design Branch. The Ministry of Works and Transport requires strict conformance to the IBC for the larger buildings that they are responsible for approving. Very few homes fall into this category and as such are not held to this higher standard of review, he said.

Granger mentioned that the regional corporations generally maintain full approving responsibility for most homes and their approval strategy is based on the opinion of the building inspector/engineer vs conformance with a specific code.

“The construction industry is unregulated and with homeowners having access to less resources, they often seek the lowest prices. Often the cheapest contractor may not have the experience to get the job done properly and problems arise,” he said.

Likewise, Carrington cited the absence of enforcement of regulation and the need for these laws to be updated to meet the advent of new building technologies and demand for housing, commerce, industry and recreation (increase in density and master planning).

He acknowledged while professional bodies such as the Board of Engineering, and the Board of Architecture of Trinidad and Tobago continue to champion the cause for a better built environment locally, ultimately, it is only possible with the help of policy and law makers.