What is an extension of time (EOT) in construction?

An EOT is additional time granted to the contractor to complete the works when a delay caused by an excusable event pushes out the completion date. It protects the contractor from liquidated damages for the delayed period and, where the event is also compensable, can open the door to recovering prolongation costs. Entitlement depends on the contract terms and on timely notice.

Why are contemporaneous records so important for delay claims?

Tribunals and adjudicators give far more weight to records made at the time of an event than to accounts reconstructed later for the dispute. Contemporaneous records fix the date, establish the cause without hindsight, and show the effect on actual progress. A daily site diary with attached photos and weather data is the most reliable evidence you can bring to a construction delay claim.

What is the difference between as-planned and as-built?

As-planned is the accepted baseline programme: the sequence and durations you committed to. As-built is what actually happened on site, reconstructed from daily records, progress photos and labour returns. Delay analysis compares the two; the gap, and its cause, is the claim. The as-built half is built almost entirely from your daily documentation, so weak records weaken the whole analysis.

How quickly must I give notice of a delay?

Most standard forms make notice a condition of recovery. FIDIC, for example, commonly requires notice within 28 days of the contractor becoming aware of the event, and missing the window can forfeit the entitlement entirely. The general rule across contracts is to notify early, in writing, reference the clause, and keep updating the claim as the delay develops.

Can good documentation help recover prolongation costs?

Yes. Prolongation costs such as extended site overheads, supervision and standing plant must be proved for the actual delay period, not estimated. A daily record that links each delay window to the resources genuinely on site lets you recover what you actually spent. Without that day-by-day picture, tribunals tend to cut prolongation claims to a conservative estimate.

Proving Construction Delays: A Practical Guide to EOT Claims

Construction delay claims succeed or fail on evidence, not arguments. To win an extension of time (EOT) and recover prolongation costs you must prove what was planned, what actually happened, why the difference was the employer\'s risk, and that you gave timely notice. The single most important factor is contemporaneous documentation kept day by day, not reconstructed months later.

This guide explains the common causes of delay, why daily records matter, how the as-planned vs as-built comparison works, what notice you owe, and which evidence actually persuades an adjudicator or tribunal.

Common Causes of Construction Delay

Not every delay entitles you to time or money. The contract allocates risk, and your claim must show the delay falls on the other party\'s side of the line. Typical causes include:

Late or defective information \\u2013 drawings, specifications or instructions issued late by the employer or designer.
Variations and change orders \\u2013 additional or altered scope that pushes out the programme.
Differing site conditions \\u2013 unforeseen ground, contamination or existing structures.
Employer-caused disruption \\u2013 late possession of the site, access restrictions or delayed approvals.
Exceptional weather \\u2013 conditions beyond what an experienced contractor should have allowed for.
Third-party and statutory delays \\u2013 utilities, authorities or nominated subcontractors.

Each cause maps to a contractual entitlement category. Under FIDIC and most common-law forms, delays are sorted into excusable and compensable (time and money), excusable but non-compensable (time only, often neutral weather or force majeure), and non-excusable (contractor\'s own risk).

Why Contemporaneous Records Win

Tribunals trust records made at the time over witness memory reconstructed for the dispute. A site diary written on the day, with photos and weather attached, carries far more weight than a spreadsheet assembled two years later by claims consultants.

Contemporaneous records do three things a retrospective narrative cannot: they fix the date an event occurred, they establish cause without hindsight bias, and they show the delay\'s effect on actual progress. If you cannot show when a problem started and how it rippled through the works, even a genuine entitlement can collapse for lack of proof. For the broader compliance picture, see our guide on construction documentation legal requirements.

As-Planned vs As-Built: The Core Comparison

Every delay analysis compares two pictures of the project:

As-planned \\u2013 the accepted baseline programme: the sequence, durations and logic you committed to at the outset.
As-built \\u2013 what actually happened on site, reconstructed from daily records, progress photos and labour returns.

The gap between the two, and the reason for it, is your claim. Common methods include as-planned vs as-built, impacted as-planned, time impact analysis and windows analysis. Whichever method an expert chooses, the as-built half is built almost entirely from your daily documentation. A weak or missing site diary forces the analyst to guess, and a tribunal will discount guesses.

Delay cause	Entitlement (typical)	Evidence that wins
Late design information	Time + money	Dated diary, RFI log, correspondence
Variation / change order	Time + money	Instruction record, marked-up drawings, photos
Differing site conditions	Time + money	Photos, survey, diary at discovery
Exceptional weather	Time only (often)	Daily weather data, lost-day log, photos
Contractor resourcing	None	(Non-excusable)

Notice Requirements You Cannot Ignore

Almost every standard form makes notice a condition of recovery. Under FIDIC, the contractor must give notice of a delaying event within a defined period \\u2013 commonly 28 days of becoming aware \\u2013 or risk losing the entitlement entirely, even if the delay was genuine. The principle is general across common-law contracts: notify early, notify in writing, and keep notifying.

Good practice, regardless of jurisdiction:

Give early warning as soon as a likely delay is foreseeable, not when it bites.
Serve formal notice within the contractual window, referencing the clause.
Submit particulars \\u2013 the cause, the affected activities and the estimated impact.
Update the claim as the delay unfolds; a single static notice rarely suffices.

Your daily records are what let you serve notice within days rather than weeks. If your team logs events as they happen, the notice almost writes itself.

Evidence That Actually Wins EOT Claims

A persuasive delay claim rests on a stack of mutually corroborating records. The strongest combination:

Site diary \\u2013 the daily narrative of labour, plant, activities, instructions and events. This is the backbone of any construction diary.
Timestamped photos \\u2013 visual proof of progress, conditions and obstructions, tied to a date and location.
Weather data \\u2013 objective, per-day records to support neutral-event or exceptional-weather claims. See weather documentation in construction.
Correspondence \\u2013 RFIs, instructions, minutes and emails establishing who knew what and when.
Programme and progress data \\u2013 the baseline and regular updates that anchor the as-built reconstruction.

The key word is *contemporaneous*. Evidence created on the day, automatically dated and hard to alter, is what carries weight. Reconstructed records invite the question every defendant asks: how do we know this is accurate?

How Daily Documentation Supports Prolongation Costs

Winning the time is only half the battle; recovering money is the other. Prolongation costs \\u2013 extended site overheads, supervision, plant standing time \\u2013 must be proved for the actual period of delay, not an average. That means showing what resources were genuinely on site during each delay window.

A complete daily record links the delay event to the resources affected: the crew that stood idle, the crane that could not be demobilised, the supervisor retained on site. Without that day-by-day resource picture, prolongation claims get cut to whatever the tribunal feels comfortable estimating. With it, you recover what you actually spent.

This is exactly where a structured digital diary earns its keep. docubau lets your team capture entries by WhatsApp, Telegram or app, automatically attaches weather data and timestamped photos to every entry, and exports a clean PDF record \\u2013 the contemporaneous backbone an EOT and prolongation claim needs. Plans start at \\u20ac49/month with a 14-day free trial.

Strong documentation does not just help you win disputes; it deters them. When the other side sees a complete, dated, photo-backed record, weak counter-arguments tend to evaporate before they reach an adjudicator.

Start your free trial \\u2192