How to Manage Weather-Related Impacts in Construction Projects

What Weather Counts as ‘Inclement’?

Inclement or severe weather is any weather event that makes construction unsafe or unreasonable – think heavy rain, storms, extreme heat, cyclones, hail, flooding, or high winds.

While all those events can and do affect sites across Australia, rain is the most common form of inclement weather. Even relatively light showers can prevent certain forms of work, such as concreting or roofing, which can lead to a ripple effect in project delays.

Wet weather isn’t just a feature of the tropics, either. In 2022, for example, Sydney experienced its wettest year on record – 2,522.8 millimetres of rainfall (double its annual average), which was the result of three consecutive La Niña events. Another example: South-East Queensland was predicted to have a dry 2023–24 summer, but instead experienced violent storms followed by 421.9 millimetres of rainfall (30.1% above average).

The effects of climate breakdown mean that inclement weather is no longer unusual. Construction projects, no matter where in Australia they’re located, need to have mitigation strategies built in from the start.

Cost Impacts of Inclement Weather

While inclement weather can physically damage sites – particularly before structures become watertight – most costs are incurred through delays. These costs fall into three different buckets:

• client-side costs (such as increased holding costs due to delayed delivery)
• labour costs (most awards stipulate increased rates or guaranteed hours during inclement weather)
• material costs (which may increase as a result of delays or replacements required due to damage).

Whether the labour and material costs are borne by the principal (the client) or the head contractor depends on each project’s contract. Similarly, while client-side costs can be recovered through liquidated damages, the feasibility of any claim rests upon each contract’s extension-of-time (EOT) clause, whether inclement weather is a qualifying cause of delay, and how this is managed with the project stakeholders. If the head contractor has a legitimate EOT claim, the principal can’t claim related liquidated damages.

The exact scale of weather-related costs varies from project to project. One analysis found that Sydney’s 2022 rainfall caused medium-to-high-density apartment builders to suffer cost increases of 4%.

Other Risks

Delay- and damage-related costs are the biggest risks presented by inclement weather. It can, however, also create significant WH&S liabilities.

During weather events, workers are likely to be exposed to health and safety hazards. These can include heat stress (during high temperatures), slip hazards (during rainfall), unsecured/unstable site elements, and dust storms (during high winds). Injuries can lead to reductions in workforce capacity (which can be particularly problematic if the injured worker is a skilled contractor), workers’ compensation claims, and, potentially, negligence-related damages.

How to Manage Weather-Related Impacts

As the principal of a project, you can’t control exactly how your head contractor manages weather events. Instead, you and your project manager’s focus should be on contractual clarity – making sure each party understands which risks they own, when EOT claims should be lodged, and what measures can be taken to minimise costs.

Clearly Define ‘Inclement Weather’ and Risk Ownership

Your agreement with your head contractor should clearly define what inclement weather is and who is responsible for weather-induced costs. Any ambiguity can leave you open to expensive legal challenges.

For example, terms like ‘extreme weather’ or ‘abnormal conditions’ could be problematic if left unclarified; both, interpreted literally, would likely refer to weather outside the historical averages for a given location and time of year. In reality, though, any weather that impedes safety or productivity should be considered ‘inclement’.

Depending on the type of inclement weather being defined, including specific measurements can be helpful. For example, ‘extreme heat’ could be defined by maximum temperature and humidity ranges, whereas 24-hour rainfall totals could be useful for defining ‘heavy rain’. Keep in mind that certain types of weather may have their own definitions under union rules or legislation; while these definitions don’t necessarily need to be applied, they should be considered.

Whatever definition you and your head contractor agree on should be reasonable. For instance, while a day of heavy rain might be covered as ‘inclement weather’, the site would need to be dewatered the following day, which might not be covered. (In that example, adding ‘clean-up’ buffer periods to certain types of events could be a fair middle ground.)

Historically, most contractors were expected to bear the risk of weather-related impacts. This is becoming less common as many head contractors are looking at ways to minimise their risk profile in the post-COVID-19 era.

Account for Possible Events in the Contract Program

Contract programs should include provisions for inclement weather. These should normally be based on historical inclement weather medians – for example, the number of days in a given month over the past 10 years with rainfall of more than 10 millilitres per day or air temperature and humidity exceeding 29°C and 75% respectively.

While calculating the projected number of days lost should typically be the responsibility of the head contractor, your project manager should check any estimates to make sure they’re realistic. Overestimates can lead to unnecessarily inflated project timelines; underestimates can result in schedule blowouts and EOT claims.

Relevant data can be accessed via the Bureau of Meteorology (BOM), although some metrics, such as air temperature, can vary heavily depending on site location. If possible, start recording on-site conditions as far in advance as possible to make sure your contractor’s estimates are accurate.

Avoid High-Risk Periods

One of the simplest ways to manage inclement weather is to work outside of high-risk periods. That’s not always feasible – especially for larger projects – but, where timelines permit, scheduling major construction stages outside of December, January and February (or November to April in the Northern Territory) can be a good idea.  

Reduce Time on Site

In scenarios where inclement weather is predicted for a significant number of days, your project manager and head contractor should aim to reduce time on site as much as possible. Reduction strategies can range from off-site construction (choosing prefab over on-site assembly, for example) to different project management approaches (doubling output during non-inclement weather or changing construction sequences).

Keep in mind that these strategies don’t just apply to on-site work. Inclement weather can affect your supply chain too, so choose suppliers whose production facilities are relatively weatherproof.

Implement Environmental Control Measures

Inclement weather can’t be avoided, but it can often be controlled and mitigated. Your head contractor should have measures available to manage the effects of wind, dust, and rain.

Basic steps include:

• securing loose materials that could be picked up by wind
• keeping water-reactive materials like cement in elevated, covered locations
• properly removing/storing debris
• suppressing dust through water spraying
• managing dust and wind through board or sediment fences.

Measures for managing rain specifically include:

• properly siting sediment basins
• implementing stormwater drains
• ensuring access roads are accessible and stable even after heavy rain
• installing filter strips (where required)
• storing heavy vehicles in easily accessible locations that aren’t likely to become boggy.

You or your project manager can check the environmental control measures used by different vendors during the tendering process, and, where required, contractually obligate their use. (Many environmental control measures may be required for compliance purposes anyway.)

Track the Weather

Tracking local climate conditions is essential for both WH&S compliance and assessing EOT claims. While your project manager can use data from BOM and other third-party meteorology organisations, BOM’s measurements are derived from their local weather station – which may or may not reflect on-site conditions. (Third-party data may also lack granularity; for example, did heavy rainfall on a given day occur during that day’s working hours or overnight?)

A better approach is to install your own weather station. Most commercial-grade models include a full suite of sensors – rainfall tipping buckets, dust monitors, air temperature and relative humidity sensors, wind gauges – as well as data logging and automated reporting.

Keep in mind that larger sites – particularly those with diverse topographies – may need multiple sensors set up at different locations.

Set Up Time-Lapse Photography

On-site weather stations are an excellent way to measure inclement weather conditions. But, in some scenarios, there might still be ambiguity around EOT claims – think light rainfall that turns a site boggy due to high soil saturation.

Time-lapse photography can add a qualitative dimension to your weather station’s data. If, for example, a contractor’s evidence for an EOT claim didn’t match the data, you could cross-reference the relevant photographs. Combined, the two measurement systems are an excellent way to quickly resolve claims and, for multi-year projects, enable more accurate scheduling. 

Choosing the Right Project Manager

Understanding the theory of weather management and successfully implementing the strategies we’ve talked about are two different things. Contract negotiations, in particular, need the right project manager – someone who knows how to draft viable terms without crippling your head contractor.

Sometimes, that person might be your in-house project manager or your existing client-side firm. But, if their expertise lies in different parts of the project management space, it’s often worth involving another vendor.

At Empire, for example, a flat organisational structure means that our senior leadership is actively involved in every project. When contract negotiations are underway, you’ll have input from senior members of our team with decades of industry experience.

Our team also have strong technical knowledge – the result of both tertiary qualifications and in-field experience. That can help us work effectively with your head contractor to manage complex delivery and supply chain problems. And, with around-the-clock support, we’ll always be available during weather events, regardless of whether they occur at night, on weekends, or during public holidays.

It’s not enough to be aware of inclement weather management strategies. You need a PM team that can execute them successfully – and, on more than 220 projects, that team has been us.