Brick and Masonry
Climate change may mean growing role for time-tested products
Construction Durability
Brick provides long service life, and can also be re-used in new construction.
by Judy Pryma.
Tornados, hurricane spin-offs, torrential rains, floods, heat waves and ice storms.
As such incidents become more common in Canada, the ability of structures to withstand the effects of extreme weather is of growing importance to designers and builders.
“We’re accustomed to tolerating high levels of damage on rare occasions, like the one in one hundred year storms,” notes Dr. Robert G. Drysdale, professor of civil engineering at McMaster University, Hamilton, ON. “But as these occurrences become more frequent, it’s necessary to design for a higher level of protection.”
According to Environment Canada, climate change is not only causing global warming but is also responsible for the more frequent occurrence of major weather events.
“We don’t have the infrastructure to withstand the 50 year storms that now seem to be occurring every eight years,” says Environment Canada’s chief meteorologist David Phillips.
“The weather is changing and we need to design our buildings with climate change in mind.”
Dr. Drysdale, an authority on the use of masonry materials and structures, believes “masonry has extra capabilities that will enable buildings to resist unusual situations that may come about in the future as a result of global warming or other changes in weather patterns.”
More rational design
Use of masonry products – clay brick, concrete brick and block and natural or manufactured stone – has become “more of a science than an art,” Dr. Drysdale adds. He sees “rational design” as key to erecting more robust buildings that will withstand more extreme conditions.
Whether a building utilizes masonry veneer or uses a loadbearing masonry structure, designers are moving from a “working stress” design to a “limit stress” model which offers a more rational approach to utilizing the full strength of the material, he says. Rational floor layout, including configuration of hallways, also has an important effect on structural soundness.
“Great progress is being made in the use of masonry in achieving more rational design,” according to Dr. Drysdale.
“Architects and builders today are much better equipped to design rationally using brick or block. Masonry offers a lot of excess strength that combined with good design to achieve a robust configuration, ensures a more stable structure.”
According to David Phillips, relentless warming is now an established fact. As a result, he says, the question of how to deal with extremes in weather is likely to become a major issue for builders.
“It’s not just that we’re seeing slushier winters and warmer springs. Clear anecdotal evidence suggests we’re seeing more occurrences of extreme weather.”
On the day Phillips made these comments, the first tornado ever recorded in Brooklyn was reported.
The Insurance Bureau of Canada estimates that unusual weather conditions accounted for $800 million in property damage between 2000 and 2004. As extreme weather events become more frequent in the future, the strength and construction durability of exterior cladding will become even more important than it is today.
While no one expects Canada to be faced with the circumstances which led to the destruction of 300,000 homes in New Orleans, other unusual weather conditions are cropping up more frequently here.
Masonry vs weather
Masonry products have generally earned the reputation as optimum building materials that provide an effective barrier against just about any type of weather.
A recent U.S. study has shown that vinyl or fibre-cement siding can be penetrated by objects driven by a 40 kilometre an hour wind, while masonry walls can withstand wind-blown objects at speeds up to 130 kilometres.
According to Environment Canada, tornados and near-hurricanes have become more frequent in Canada. Extensive flooding, with considerable property damage, occurred in Newfoundland in August after the island was whipped by the tail-end of post-tropical storm Chantal. Edmonton this year marked the 20th anniversary of a tornado that brought winds of 400 kilometres per hour, killing 27 people and caused $330 million property damage.
Warmer weather has encouraged Canadians to turn up their air conditioners, causing authorities to appeal for greater tolerance of higher temperatures. Clay brick and other masonry products have the capability of absorbing heat and releasing it over time, reducing dependence on artificial cooling.
The thermal mass of concrete floors and walls contributes to the creation of a passive solar energy system in such buildings. In summer, the concrete acts as a heat sink and absorbs the sun’s heat during the day. Because it takes longer for the sun to heat up a concrete building, the air conditioning load is reduced. In winter, the sun is at a low angle and penetrates well into the interior space to heat the concrete.
Preventing mould
Increased rainfall in many communities is responsible for more moisture in homes, a condition conducive to mould. The moisture resistance of masonry means less chance of mould growth. Using moisture tolerant materials such as masonry will help keep your family and home healthy.
Wood and drywall provide a source of food for the growth of mould bacteria whereas masonry does not.
A study of Fungal Mould Resistance carried out in 2003 and reported in Masonry Canada [Spring, 2004] concluded that “Under identical conditions conducive to the growth of fungal mould, no mould is produced on clay brick, concrete block and concrete, whereas substrates made of wood and paper products produce measurable amounts.”
One way that Canadian building codes deal with mould is by stipulating that a wall’s vapour barrier be on the warm side of the dew point. This requires it to be inside the wall. Where separate vapour and air barriers are used, the codes govern the relationship between them in terms of permeability.
Fire
The long tradition of heavy reliance on masonry in the Toronto area stems in part from fire codes that once dictated the use of bricks in home construction. Current codes permit a broader range of materials, although Ontario has rejected use of anything other than masonry or concrete in firewalls.
Besides masonry, vinyl and stucco are the most popular cladding materials in Canada. As a result of a recent fire in Edmonton where a condominium under construction caused damage to dozens of nearby homes clad in vinyl siding, officials are asking for changes in the Alberta building code. The heat melted the vinyl, exposing the homes to fire damage.
The fire resistance of masonry is recognized by the Insurance Bureau of Canada. Homeowners may be eligible for a discount on their insurance premium or inclusion in a preferential rate category if their home uses masonry construction.
The National Research Council is studying fire hazards connected with the use of combustible materials in housing, especially when units are built close together.
At the University of Western Ontario, a second study – dubbed the “3 Little Pigs” project – is spending $8 million to measure the effects of a Hurricane 5 force wind on a typical suburban-style house that has been built at the London airport. The wind force will be applied via pressure generators attached to the house. The project also will study the occurrence of mould. The studies will assess different types of building materials and their ability to withstand extreme conditions.
Survey shows acceptance
Nearly seven out of 10 Ontario residents say they would choose masonry materials if given an option by their builder. A survey by Leger Marketing, undertaken for MasonryWorx, showed 67 % preferring a masonry product.
Eight out of 10 said they are aware of the perceived benefits of masonry, including long life, low maintenance and superior fire resistance. Nine out of ten said they would pay more for a home using environmentally friendly building materials like masonry.
Sustainability
The environmental sustainability of masonry products extends from origin to recycling, according to industry sources. Many masonry manufacturers recycle fly ash and slag to produce a portion of the cement in their products.
A 1994 study sponsored by Natural Resources Canada and conducted by the wood industry’s research arm, Forintek, found that quarries used for making concrete consume less land and are more easily reclaimed than forestry or iron ore mining operations.
Embodied energy – the energy used in mining, manufacturing and transporting brick – is much less than aluminum, wood or even concrete, according to the American Institute of Architects. An AIA report put the embodied energy of brick at 4,000 BTU per pound, or 14,000 BTU per standard brick equivalent [SBE]. According to the U.S. National Institute of Standards and Technology, the higher energy efficiency of newer plants has since reduced the industry average to 1,239 BTU per pound.
Masonry products enhance both longevity and recyclability, keys to sustainable building, according to the industry. Clay brick and concrete block carry warranties of 100 and 50 years, respectively, compared to five years for exterior wall cladding systems made of polystyrene foam board resembling plaster or stucco.
On average, masonry products are sourced from sites fewer than 200 miles distant, while other claddings, including vinyl, are usually shipped an average of 300 miles, thus requiring more energy in transit. Concrete is frequently recycled as aggregate for new product.
The Great Wall of China, the Roman Coliseum and India’s Taj Mahal are often given as historic examples of masonry construction durability. More currently, the conversion of masonry-based warehouses to residential units, as is occurring in many Canadian cities, attests to the product’s long life and ease of conversion.
The old Gooderham & Worts buildings in Toronto, now converted to a “Distillery District” retail and cultural complex, is an example of the reuse of brick structures. A Mountain Equipment Co-op building erected recently in Winnipeg made heavy use of re-used brick.
Noise reduction
Masonry also resists noise pollution, a growing concern as urban areas intensify with traffic and population.
The mass inherent in masonry systems provides significantly better sound resistance, especially in the lower frequency ranges, than alternatives such as steel and wood stud.
The National Research Council found masonry products fully capable of meeting the critical sound protection threshold of STC 55 – a Sound Transmission Class expressed in decibels that is considered the “realistic goal” for acceptable sound insulation. Concrete blocks meet this standard when their surface is sealed with plaster or block sealer. Addition of gypsum board results in significantly higher STC ratings.
“Noise from neighbours in multi-unit buildings is a serious problem that degrades the quality of life of the residents,” the NRC noted in a report on noise pollution.
Whether for physical security, noise depletion, or protection against high winds, heavy rains and other extremes of weather, the environmentally sustainable qualities of masonry products appears to be well established.
»»» Related Information:….
Sustainable Masonry
Masonry products
Brick, concrete, stone are among the building industry’s most sustainable materials. Environmentally and economically, their attributes include:
Recyclability
Long life and construction durability. Many structures remain usable for hundreds of years. Easily convertible to new uses; warehouses to residences; industrial buildings to retail; bricks from demolished buildings can be used in new construction.
Resistance
Concrete, stone and brick structures are impervious to all but most severe weather disturbances. Minimal noise penetration, mould growth and vibration effects.
Replacement
Infrequent need of replacement means energy savings in new production. Original production has less environmental impact than forestry or plastics products.
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