Come Rain or Shine

Mother Nature versus the Construction Industry

At even the best of times, weather can put the performance of buildings and materials to the test. Reducing project downtime through preparation is vital as construction projects are easily affected by rain, wind, heat and lightning storms. Accurate weather forecasting allows construction managers to allocate resources more effectively, thereby avoiding delays and saving money on projects.

Many of Australia’s coastal regions are prone to seasonal cyclones which bring heavy rains, strong winds and the possibility of tornadoes, as well as damaging storm surge and high waves. However, storms don’t have to be that widespread to leave a trail of destruction as even localised thunderstorms can wreak havoc on a jobsite. They may occur suddenly and are especially dangerous to outdoor workers and to tall structures, particularly in open areas where there may be little time to seek shelter or little shelter available. Workers may need to seek inside protection on a ground floor away from loose materials, windows and doors, if possible.

It is safest to halt work on site when extreme conditions, such as lightning storms, are imminent. Though, as storm systems can be fast moving, sometimes the warning doesn’t come soon enough to prevent being injured or struck by lightning. Last autumn, as McConnell Dowell employees were preparing to leave construction work on Fortescue Metals Group’s Solomon rail line in advance of a storm, two men were injured as a result of a lightning strike.

Thunderstorms can also bring hail, breaking windows and damaging exposed materials. Shingles and single-ply roofs are prone to damage and, though nothing can protect from events like 2010’s hailstorm in Melbourne with its orange-sized balls of ice, roof systems that are resistant to hail need to be considered where severe thunderstorms are common.

Wind can rip sidings from exterior walls and high winds can even produce sufficient wind uplift forces to tear off roofs. Thunderstorms are often accompanied by straight-line winds that can approach hurricane speeds. Skyscrapers can sway by several feet at the top as tall, flat walls receive the full impact of wind. They are designed to take this kind of motion without damage but walls that are not structurally braced or are not designed for movement can be reduced to rubble. Even slight winds can have strong forces and installing towers or antennas on windy days can be dangerous.

Severe damage can result on building sites exposed to wind forces, in particular to roofs, unsupported masonry walls and non-completed walls of all types. An incomplete structure is more susceptible to wind damage than a finished one as buildings are not meant to sustain the kind of forces resulting from wind penetrating a building’s envelope. Before completion, large open projects such as factories and warehouses are particularly vulnerable to winds.

One of the structures most easily damaged by wind forces during construction is the large steel storage tank. Tanks under construction can be damaged by either direct pressure or suction forces caused by wind or a combination of the two. A vacuum can be created inside a tank that is designed for positive pressure in some cases and the tank will be crushed once the negative pressure exceeds the design pressure.

Construction crews must ensure that construction in process is properly braced and that all jobsite materials, including debris, are properly secured. Scaffolding is one of the things that needs to be securely fastened. In Melbourne in 2007, the scaffolding was apparently disconnected from a building in order to “enable the painters to finish” when it was caught by high winds and collapsed into the street.

Tower cranes are ‘weathervaned’ to help them survive high winds. This involves releasing the swing brake of the unit so the jib can be moved freely by the wind. The wind then pushes the jib downwind as the counterweight points upwind, balancing the tower structure.

Wet weather is a frequent reason for construction delays and increased project costs. Heavy rains can turn a construction site into a gigantic sea of mud that hinders site access and slows or entirely prevents grading, trenching, backfilling, paving and foundation work as the ground becomes soup-like. The construction of the Aspect Hunter School in New South Wales last year suffered setbacks in its building timetable after eight weeks of rain made working on the earthworks impossible. Even when the site has been properly graded to ensure drainage away from the structure and to prevent water from pooling, occasionally, wet weather related delays in schedule are unavoidable.

Flooding is always a possible result of torrential rains but in Australia, rainy weather can be additionally exacerbated by La Niña events or tropical cyclones. As a result of Tropical Cyclone Tasha’s heavy rainfalls combined with the peak of a La Niña, a series of floods hit Queensland beginning in late 2010 and left damages worth $2.38 billion. Flooding elsewhere that year caused delays in the construction of the Cotter Dam, west of Canberra, in February 2012.

After all that, it may seem odd to consider a sunny day to be a potential problem for construction but hot and dry weather can also dramatically affect a project. The solvents in paint and sealants, for example, can evaporate too quickly, affecting the curing and performance of the materials. With over fifty per cent of the country receiving an average yearly rainfall below 300mm, dry conditions are certainly prevalent.

Dry weather makes the moisture in masonry and concrete evaporate far faster than desired. Rapid evaporation produces weaker concrete and reduced bond strength between bricks and mortar. The challenge is in keeping the products wet enough that they can cure properly. Bricks can be thoroughly wetted so they don’t leach moisture from the mortar, but concrete takes days or weeks to cure in order to achieve maximum strength and durability. Covering the concrete with a membrane such as polythene, leaving the formwork in place or applying a chemical curing agent can achieve a barrier to evaporation in dry weather. Moisture can also be added to the concrete by continuously wetting the exposed surfaces with a water spray.

One of the biggest building issues with hot, dry weather is dust. Preventative maintenance is important since dust finding its way into machinery can cause accelerated wear, resulting in unexpected breakdowns. As a result, equipment must be cleaned and lubricated frequently and air filters on all equipment and vehicles need to be frequently checked and changed.

If not managed, dust settles on everything from neighbouring property to the project under construction and generates both complaints and extra work in the form of regular cleaning of interior surfaces. Using a tanker truck to spread a fine mist of water around dry areas of the site is often used to reduce the problem, as are physical barriers surrounding the site.

Mitigating the dust problem on construction sites is vital for worker safety as well. In addition to hazards caused by poor visibility, dust can cause eye, nose and throat irritation and respiratory damage. If that wasn’t bad enough, dry weather increases the chances of bush fires which will further decrease air quality dramatically. Even with other dust suppression methods, the use of personal protective equipment, such as goggles or dust masks, is often needed to prevent injury.

Hot, dry weather can be potentially dangerous to workers as it can cause dehydration or heat stroke. Drowsiness, disorientation, dizziness and fatigue are common symptoms of dehydration and must be treated immediately. The physical activity associated with construction work causes even further losses of body fluids than usual and it is imperative that this loss be replenished. A source of fresh cool drinking water on site is a must to prevent dehydration. The Construction Forestry Mining and Energy Union recommends that work cease in exposed areas when temperature exceeds 35°C and cease in all non air conditioned areas when temperatures are above 37°C. Work schedules can be altered so work can be done at cooler times.

Project managers must handle all aspects of a complex build while being at the mercy of the weather. Apart from regular news and weather updates, a number of services offer weather forecasts specifically tailored for the construction industry. Foreknowledge of upcoming extreme heat events can allow for task planning in order to avoid delays and wind forecasts can allow for planning of safe crane work.

As author Mark Twain said, “Everyone talks about the weather, but no one does anything about it.” Although weather cannot be controlled, anticipating weather events and adjusting to them for more efficient project planning is just what building professionals do.

Home Automation

Call it ‘domotics,’ and you are likely to receive a blank stare, but refer to it as ‘smart home’ or ‘home automation,’ and you will get a nod of acknowledgement. For the past few years, consumers have heard the word ‘smart’ attached to countless products and services, from food and drink to snacks like popcorn and mobile phones, which no one seems to refer to as a ‘cellphone’ anymore. Yet what, exactly, constitutes ‘smart’?

January 17, 2019, 6:28 AM AEDT