Rain Day Logs: Record Weather Delays for an Extension Claim

Why is a weather-delay log different from a rain-season buffer?

Most Thai contractors already add a rain-season buffer when they first set up the Gantt — a handful of spare days in October and November to absorb expected wet weather. That buffer is a planning tool: it protects the schedule from typical disruption. A weather-delay log is something entirely different. It is a running record of the actual disruption that happened, day by day, with timestamps and photos attached. When the monsoon delivers more disruption than the contract allows, the gap between what was expected and what actually occurred is the legal foundation of a valid extension-of-time claim. Without that log, the contractor must argue from memory against an owner who has every reason to disagree. With a dated log — on-site progress updates showing rain conditions, tasks paused and restarted, notes recording hours lost — the claim becomes simple arithmetic rather than a dispute about what happened on a specific Tuesday three months ago.

What counts as a recordable weather-delay day on a Thai construction site?

A recordable weather-delay day is one where rain, flooding, or saturated ground prevents critical-path work from continuing for a significant portion of the working day — typically four hours or more. A brief morning shower that clears before nine o'clock rarely qualifies. A day when concrete cannot be poured because of active rainfall and standing water on the slab, when a foreman sends workers home by noon because the site is too wet to work safely, or when machinery cannot move without sinking all count. The practical boundary is this: record the event, describe which tasks stopped and for how long, and let the contract language and any negotiation decide whether the day qualifies. Recording more events rather than fewer costs nothing and loses nothing; under-recording a genuine delay day permanently forfeits the entitlement. Thai construction contracts commonly set a monthly threshold of six to ten allowable rain days, after which additional lost days become claimable.

How do you log a weather-delay day in SiteBoard in real time?

The moment a foreman decides that rain or site conditions have stopped significant work, the fastest record is an on-site progress update submitted from their phone that same day. The update should include one or two photos of the site condition — pooled water on the footing, rain falling on uncovered structural steel, workers sheltering — plus a note stating which tasks stopped and roughly how many hours were lost. No special form is needed. The timestamp on the progress update is the legal-grade date record. In the Gantt planning view, adjust the end date of any paused task to reflect the lost time. Do this the same day the delay occurs, not at the end of the week. A log assembled at the end of the month looks assembled at the end of the month. A daily log with field photos, each submitted when the event happened, looks exactly like what it is: a real-time record of conditions on site.

What supporting evidence makes a weather-delay claim difficult to dispute?

The strongest supporting evidence is a Thai Meteorological Department record for the nearest monitoring station, downloaded after the season and filed alongside the SiteBoard on-site progress updates. The TMD publishes daily rainfall data by province; if the official record shows 55 millimetres of rain on a day the foreman logged a stopped site, the two records together leave almost no room for dispute. On-site photos from the progress updates — showing standing water, wet concrete forms, or sheltering workers — add a site-level layer that a remote weather station cannot provide. The Gantt itself, with tasks paused on specific dated days and restarted when conditions improved, shows the schedule impact. Together these three sources — weather station data, progress photos, and the Gantt — make a claim nearly impossible to challenge in good faith.

How many rain days per month are considered normal in Thai construction contracts?

Thai residential and commercial construction contracts rarely specify an exact number of allowable rain days, but an industry norm of six to ten days per month during the peak monsoon season from September through November is widely understood among experienced Thai contractors. Projects in the Central Plains — Bangkok, Pathum Thani, Ayutthaya, Chachoengsao, Nonthaburi — face a different baseline than projects in Phuket or Chiang Rai. If the contract is silent on weather, the contractor can still pursue a claim under the force-majeure provisions that appear in most standard Thai construction agreements, provided the disruption demonstrably exceeded what was reasonably foreseeable for that location in that season. Knowing the regional baseline before filing any claim helps frame the request in terms the owner will find credible rather than opportunistic.

A real example: a townhouse project in Chachoengsao during October 2026

A contractor managing a four-unit townhouse development worth 2.4 million baht in Chachoengsao faced an exceptionally wet October 2026 with seventeen working days disrupted by rain, against a contract baseline of eight. The nine extra days pushed concrete work and MEP rough-in tasks back by two weeks, threatening the December handover milestone. Because the foreman had logged each rain day as an on-site progress update the same day it occurred — with photos of flooded footings and the partly finished slab — the contractor had a clean nine-entry log with timestamps. They downloaded the TMD daily rainfall data for Chachoengsao province, matched it to the nine logged entries, and presented the Gantt showing all affected tasks shifted two weeks alongside the evidence. The owner agreed to a two-week extension at the next site meeting without dispute, citing the clear contemporaneous documentation as the reason.

How do you share a weather-delay update with the owner through SiteBoard?

After adjusting the Gantt to show the paused tasks and the new projected completion date, share the owner sharing link and send a written message — LINE is sufficient — summarising the rain days logged and the revised schedule. The message should state how many days are being claimed, the new expected completion date, and direct the owner to the Gantt for the full detail. This works better than a phone call for two practical reasons. First, the owner can see the evidence in the Gantt directly rather than hearing a verbal account they have no way to verify. Second, the written message creates a record that the owner was informed on a specific date and was given the revised schedule at that time. Owners who are shown data rather than told a story are far more likely to accept the explanation quickly, especially when the on-site progress updates include rain photos they can see themselves.

FAQ: What if the construction contract has no weather clause?

Many Thai residential construction contracts drafted by individual contractors do not include an explicit weather clause. In that case, exceptional rainfall that causes significant delays can still be claimed under the force-majeure section, which covers events genuinely outside the reasonable control of either party. The practical requirement is that the contractor must notify the owner in writing within a reasonable period and must not have caused or worsened the disruption. In practice: send a written notice — LINE or email — on the day you log a significant rain event, keep the on-site progress update as the dated evidence, and file the formal claim at the end of the wet period with the full log attached. Sending written notice the same day the event occurs is the safest habit regardless of whether the contract has an explicit weather clause or not.

FAQ: Can you claim a rain day when the rain has stopped but the ground is still too wet?

Yes. A day when the rain has stopped but saturated ground, flooded trenches, or a wet slab makes it impossible to perform critical-path work safely or productively is still a weather-caused delay. The standard is whether a reasonable and experienced contractor would have proceeded with the specific work on that day given the visible site conditions. A day where foundation steel cannot be placed because the footing trench is still flooded, even if the last rain fell overnight, qualifies. Document these conditions with a photo from the on-site progress update: a picture of the flooded trench or the wet slab with a note explaining why work cannot proceed. This evidence is especially important for conditions-based delays because the owner cannot verify the site state from a weather station report alone — the field photo is the essential piece.

FAQ: What is the typical process for formally submitting a weather-delay extension claim in Thailand?

The process has three practical steps. First, give contemporaneous written notice each day or cluster of days that a weather delay is being recorded — a LINE message or site diary entry sent the same day is enough. Second, at the end of the rain period compile the complete log: on-site progress updates with timestamps and photos, the TMD rainfall data matched to each logged day, and the Gantt showing original and revised completion dates for each affected task. Third, send a formal written request for an extension of time stating the number of days claimed and referencing the log as supporting evidence. Thai courts and construction arbitration panels consistently give greater weight to contemporaneous records than to after-the-fact reconstructions, so the habit of logging rain events in SiteBoard on the day they occur is the single most valuable step of the three.