Weather delays in construction are one of the leading causes of project delays. Despite including estimated weather days in contract durations and the availability of historical forecasts, the process of accurately estimating, tracking, and reporting weather delays in construction is often inadequate. In most agreements—including the default language of the AIA (American Institute of Architects) forms—the Contractor will be entitled to a day-for-day extension of the project schedule for each unanticipated weather delay that impacts the critical path.
While most project schedules account for a certain number of weather days, they are frequently over- or under-estimated, leading to misunderstandings among stakeholders. Although the clarity of contract language can help define expectations surrounding weather delays, it can also contribute to further confusion between parties.
To add more complexity to an already intricate issue, the real-time tracking of weather days and their effect on onsite activities often falls short, with communication and notifications delayed long after the actual impacts occur. All of these factors combine to make the identification and quantification of weather delays in construction a common pain.
How prevalent are weather delays in construction? Research shows that weather delays impact 45% of construction projects worldwide each year, costing billions of dollars in additional expenses and lost revenue.
This blog aims to equip both Owners and Contractors with the tools needed to better quantify weather-related impacts and minimize disputes. The following steps provide a structured approach to managing weather delays and resolving the long-standing debate over their impacts on construction projects.
Steps to Accurately Estimate and Track Weather Delays in Construction Projects
1. Identify Potential Weather Impacts for Your Project
To accurately assess weather delays in construction, the estimating and scheduling teams should work with superintendents and project managers to determine which weather conditions could disrupt project activities. Common concerns like rain and extreme cold are well known, but wind and visibility issues can also significantly impact operations – such as tower crane usage or placing large materials. Additionally, location-specific factors like local, regional, and seasonal weather patterns must be considered to capture the full range of possible impacts.
2. Document Which Trades Will Be Affected by Each Type of Weather Impact
Next, identify the specific trades that could be affected by each weather condition. For instance, site work and outdoor trades (e.g., foundations, structure, enclosure) are often vulnerable to excessive rain and cold. Conversely, indoor trades (e.g., MEP, framing) may be disrupted by extreme cold but are usually unaffected by rain. Wind and visibility concerns may affect the installation of heavy equipment. By correlating each trade’s schedule with anticipated weather patterns, you can better understand when and where weather might cause delays.
3. Establish Acceptable Weather Thresholds for Impact
Typically, there are four factors to consider before a weather-related extension should be allowed:
- The delay meets the terms as written in the contract.
- The weather conditions affect the project.
- The weather conditions are out of the normal range for the region and the season.
- There is detailed documentation explaining how the weather affects a given project phase.
Routine weather events, such as light rain or moderate cold, should not pause work. However, it is essential to set agreed-upon thresholds that define when weather conditions exceed normal limits and begin to impact productivity. For example, rain exceeding 0.25 inches during working hours or temperatures falling below 20°F may justify stopping work. Establishing these thresholds beforehand ensures all parties understand when weather delays in construction are justified, helping to minimize disputes over future claims.
4. Estimate Planned Weather Days per Month Using Historical Data
Once weather thresholds are established, the next step is calculating how many days will likely meet or exceed these conditions over the project duration. The best approach is to analyze historical weather data, typically available from sources like the National Oceanic and Atmospheric Administration (NOAA). To estimate planned weather days:
- Quantify the number of weather-impacted days for each month over the last 10 years based on the criteria set in Step 3.
- Average the number of impacted days for each month to account for seasonal variability. For instance, to estimate the weather delays in April, calculate the average number of April impact days over a decade.
This analysis provides a reliable estimate of expected weather delays, which should be incorporated into the project schedule. Note that these planned delays are part of the baseline and typically not eligible for time extensions.
Table 1 – 10-Year Historical Weather Day Actuals and Average
Important Considerations for Calculating Average Weather Days
When calculating the average number of “excessive” weather days, it is crucial to include all relevant weather conditions without double-counting. For instance, if a day is both extremely cold and rainy, it should be recorded as a single weather day, not two.
Additionally, only count “workdays” when compiling weather data and exclude weekends unless the project schedule explicitly includes weekend work. Refer to the example below from NOAA, which highlights working days where rainfall exceeded 0.5 inches or unusually high winds were recorded.
Table 2 – NOAA Weather Report for Mobile Regional Airport 08/2005
5. Ensure that Contract Language is Clear on Estimating and Quantifying Weather Delays
The contract must clearly define the process for estimating and quantifying weather impact days. Without detailed contract language, there are no formal guidelines for preparing a weather extension request. Contract terms should outline what constitutes a weather day, how the estimated number of weather days was determined in the baseline schedule, and the process for verifying if a weather day meets the established criteria. This clarity forms the foundation for assessing the validity of any weather-related claims.
6. Capture Actual Weather Data in Daily Reports and Download Monthly from a Weather Tracking Site
Accurate daily logging of weather conditions in job site reports is essential for supporting a claim. Be precise – if there was a drizzle, don’t exaggerate by reporting heavy rain. If the temperature drops significantly, record it. Supplement the reports with visual evidence, such as photos or videos, to document the actual site conditions. For example, capture images of wet areas, low visibility, or strong winds. Since weather stations may be located far from the site, it’s crucial to document site-specific conditions and compare them with data from the nearest weather station.
It should be noted that this exercise has been facilitated by the increased accuracy and timeliness of weather reports. In fact, it’s reported that a four-day forecast today is as accurate as a one-day forecast 30 years ago.
7. Regularly Quantify Weather Days and Compare Estimated vs. Actual Impacts
At the end of each month, calculate the actual number of weather impact days and compare them to the estimated values for that month. If actual weather days exceed the planned allowance, the contractor should be permitted to request additional impact days beyond those included in the baseline schedule.
8. Confirm Weather Impacts on the Critical Path
Before submitting a request for a time extension due to weather, it is vital to show that the weather event affected the critical path. Without this evidence, any claim for additional days is likely to be challenged. For instance, if a building is enclosed and interior work such as drywall installation is underway, heavy rain outside – while potentially severe – may not impact the critical path. To support a weather delay claim, it is crucial to demonstrate that the weather event directly delayed critical path activities.
9. Submit Weather Delay Requests Regularly and Contemporaneously
It is best practice to submit weather delay requests on a regular basis, ideally monthly. Requests made long after the delay occurred, particularly when other delays have compounded the schedule, can appear disingenuous. Consistent tracking and timely submission of weather-related claims ensure that the impact is understood and documented close to the event, increasing the credibility and acceptability of the request.
By following these recommended steps, you can more effectively manage weather delays, reducing the likelihood of overstated claims and minimizing the potential for disputes. However, it is equally important to recognize common pitfalls in preparing and responding to weather delay requests.
What to Avoid When Preparing and Responding to Weather Delay Requests
In addition to the above-recommended practices, the following practices should be avoided when managing weather delay requests.
1. Avoid Placing Activities Representing Planned Weather Impacts Directly in the Schedule
Critical Path Method (CPM) scheduling and schedule analytics are already complex, and adding activities to represent anticipated weather impacts can complicate things further. A common but illogical practice is inserting long-duration activities at the end of the schedule, logically tied as a direct predecessor to the project completion milestone. Each time a weather day occurs, a day is deducted from this “original duration.” While this method captures end-date impacts, it fails to properly reflect how weather directly affects the critical path during actual weather events.
2. Avoid Claiming a Weather Impact for Every Single Day it Rains or is Colder than Normal
Weather impact requests that claim delays for every day it rained, even slightly, often lead to inflated delay claims. Not all weather events justify a delay. A careful review is needed to ensure that the request aligns with contractual guidelines. A reasonable approach that considers established thresholds is essential for supporting weather delay claims. Failing to do so can raise concerns over the validity of the calculations.
3. Avoid Claiming Weather Days When the Critical Path is in Non-Weather Sensitive Activities
Another common issue is claiming weather-related delays when the critical path involves activities that are not sensitive to weather conditions. This results in overstated claims and is often seen as “reaching” for delay justifications. Such practices not only undermine the specific request but can also call into question the validity of other delay claims.
How to Incorporate Expected Weather Impacts into the Project Schedule
Since most construction budgets and timelines account for weather impacts, it is essential that the project schedule reflects these anticipated conditions. Incorporating weather impacts effectively measures that the planned delivery date contemplates potential delays. While several methods exist to achieve this, two approaches are considered best practice:
1. Build Weather Impacts into the Durations of Weather-Sensitive Activities
The first approach is to integrate weather impacts directly into the durations of all weather-sensitive activities. (Note: you can test this in SmartPM by modeling the effect of impacts in the Project Workspace). This includes activities such as site work, foundations, structures, enclosures, MEP, and drywall. While estimating durations doesn’t have to be exact, it should take month-to-month weather patterns into account. One risk with this approach is that unanticipated delays could push some activities into different seasons, which may have varying weather impacts. For example, pouring concrete in the summer would likely face fewer interruptions from rain compared to the challenges of cold winter conditions.
2. Incorporate Weather Impacts into the Scheduling Program’s Calendar
The second approach is to build weather impacts directly into the scheduling program’s calendar. This involves inserting non-working days in line with the number of expected weather-impacted days for each month. For example, if four weather-impacted days are anticipated in a given month, you can adjust the work calendar accordingly.
Table 3 – Weather Calendar w/ Holidays
This method is often the easiest and most accurate, as it adjusts the overall project duration to account for weather delays while ensuring that weather-sensitive activities align with the actual timing of their impacts.
How to Incorporate Actual Weather Impacts into the Project Schedule
In addition to estimating future weather impacts, it is also considered good practice to log actual weather delays in the project schedule as they occur. This provides a reliable record that can support any requests for time extensions, reducing the risk of disputes.
The best way to document actual weather delays in construction is by inserting a one-day “as-built” activity for each weather day. It’s important that these activities are recorded only as historical entries, with actual start and finish dates before the current data date. These entries should not be linked logically to other activities in the schedule, as their purpose is simply to document weather events rather than adjust the schedule. This documentation serves as a solid basis for any weather-related time extension requests.
Ensuring Fair Management of Weather Delays in Construction Projects
While weather delays in construction are common, disagreements over their handling do not need to be. It is crucial to establish clear contract terms that define expected weather days, explain how weather impacts will be quantified, and outline how they will be managed from both a cost and schedule perspective. Regularly comparing estimated versus actual weather delays using the agreed-upon criteria will help avoid disputes and ensure that weather delays are properly accounted for in project schedules.
