Construction Weather Delays in the UK: How to Document, Claim, and Plan Around Bad Weather on Site

British weather does not care about your programme. Rain, frost, wind, and flooding cause an estimated £1.2 billion in construction delays across the UK every year. Yet most contractors handle weather disruption reactively — losing days on site, then struggling to prove the impact when it is time to claim an extension of time.

The difference between a successful weather delay claim and a rejected one almost always comes down to documentation. This guide explains how UK site managers can properly document weather delays, build credible extension of time claims, and use forecasting tools to plan around disruption before it happens.

Understanding Weather Delay Clauses in UK Construction Contracts

Most standard form contracts in the UK allow extensions of time for weather delays — but the bar for evidence is higher than many contractors realise.

JCT Contracts

Under JCT 2016 clause 2.29.9, the contractor can claim an extension of time for “exceptionally adverse weather conditions.” The key word is exceptionally. Normal British rain is not enough. You need to demonstrate that the weather was significantly worse than what could reasonably be expected for the location and time of year.

NEC Contracts

Under NEC4 clause 60.1(13), a compensation event arises when weather is recorded within a calendar month as a weather measurement which, by comparison with the weather data, is shown to occur on average less frequently than once in 10 years. This is more objective than JCT — you need meteorological data comparison.

What Both Require

Regardless of contract form, you need:

1. Contemporaneous site records showing weather conditions at the time of disruption
2. Evidence of impact — not just bad weather, but proof that specific works could not proceed
3. Comparison data showing the weather was abnormal for the location and season
4. Timely notification to the contract administrator or project manager

How to Document Weather Delays Properly

Documentation is where most claims fail. Here is the evidence you should be capturing:

Daily Weather Records

Your site diary should record weather conditions at least twice daily — morning and afternoon. Include:

• Temperature: Minimum and maximum, especially important for concrete pours (below 5 degrees Celsius is problematic) and roofing works
• Rainfall: Duration and intensity, not just “rained today”
• Wind speed: Critical for crane operations (most tower cranes shut down at 38 mph), cladding, and work at height
• Ground conditions: Is the site waterlogged? Can plant operate safely? Can excavations proceed?
• Visibility: Fog can halt crane operations and certain highway works

Impact Records

Recording the weather is only half the job. You must also record what could not be done and why:

• “Brickwork suspended from 09:30 due to sustained rainfall — mortar cannot be laid in wet conditions per BS 5628”
• “Tower crane stood down at 11:15 — wind speed exceeded 35 mph sustained”
• “Concrete pour postponed — overnight temperature fell to -2 degrees and ground frozen to 100mm depth”

Generic entries like “rain stopped work” are almost useless in a claim. Be specific about the trade, the time, and the technical reason the weather prevented that work.

Photographic Evidence

Timestamped photographs transform a diary entry into compelling evidence:

• Standing water on the site
• Crane anemometer showing wind speed
• Frozen ground or frost on materials
• Flooded excavations
• Workers stood down and site inactive

Making the Claim: Step by Step

Step 1: Give Timely Notice

Under most contracts, you must notify the contract administrator of a delay event promptly — usually within 7 to 28 days depending on the contract. Late notification is the single most common reason weather delay claims are rejected.

Step 2: Compile Your Evidence Pack

Gather your daily weather records, impact notes, photographs, and programme information into a single package. Include:

• Marked-up programme showing the affected activities
• Daily site diary extracts for the delay period
• Met Office historical weather data for comparison
• Photographs with timestamps

Step 3: Demonstrate Exceptionality or Frequency

For JCT contracts: Compare actual weather against Met Office 30-year averages for the nearest weather station. Show that the conditions were statistically unusual.

For NEC contracts: Obtain weather data from the contract weather station and compare against the 10-year return period threshold.

Step 4: Quantify the Delay

Show exactly how many working days were lost, which activities were on the critical path, and the resulting impact on the completion date. A delay analysis using impacted as-planned or time impact analysis methodology strengthens the claim considerably.

Planning Around Weather: Proactive Strategies

The best way to deal with weather delays is to minimise their impact before they happen:

Monitor Forecasts Daily

Checking the weather forecast should be part of your daily planning routine. A good construction weather app gives you site-specific forecasts that go beyond the generic BBC Weather report — including wind speed at height, ground frost risk, and precipitation probability by hour.

Schedule Weather-Sensitive Works Strategically

If you know concrete pours are sensitive to temperature and rain, do not schedule them for November if you have programme flexibility. Roof coverings, external renders, and landscaping are similarly weather-dependent — plan them for the most favourable window.

Build Float into the Programme

A programme with zero float is a programme waiting to fail. Historical weather data for your region tells you how many lost days to expect per month. Build this into your baseline programme and you will absorb normal disruption without needing to claim.

Have Wet Weather Contingency Plans

When external work stops, can your team switch to internal tasks? Having a prioritised list of wet weather activities means you keep productive even when the rain comes.

How FORGE Command Helps with Weather Delays

FORGE Command integrates weather intelligence directly into your site management workflow. The app provides:

• Daily weather logging within your site diary — temperature, wind, rainfall, and conditions captured with each entry
• Timestamped photo evidence attached directly to weather-related diary entries
• Weather alerts that flag conditions likely to affect planned works
• PDF export of weather records for claim documentation

Instead of scrambling to compile evidence after the fact, your weather documentation builds automatically as part of your normal daily site routine. When it is time to make a claim, your evidence pack is already assembled.

All of this is included in the £39.99 one-time purchase — no weather module add-on, no premium tier.

Summary

Weather delays are inevitable in UK construction. Losing money because of them is not. Proper documentation — daily weather records, specific impact notes, timestamped photographs, and timely notification — turns a frustrating delay into a legitimate, evidenced claim. And proactive forecasting helps you plan around the worst of it.

The site managers who handle weather best are not the ones with the best luck. They are the ones with the best records.