Site Diary vs Allocation Sheet: When to Use Which

If you've ever found yourself wondering which form to reach for, or whether you need both, this is the answer.

The Core Difference in One Sentence

A site diary tells the story. An allocation sheet shows the maths.

Your site diary is a narrative record: what activities took place, what conditions affected them, what instructions were issued, what problems arose. It gives a reader who wasn't on site that day a clear picture of events in sequence.

Your allocation sheet is a resource record: which operatives were working, what plant was deployed, what materials were used, and which activity code each line item sits against. It gives a commercial manager the raw data to price a change, defend a claim, or reconcile a cost report.

Neither document can do the other's job. A site diary with no allocation records can tell you that a utility strike delayed the excavation gang for six hours on 14 April 2025. It can't tell you what that delay cost. An allocation sheet with no diary context can give you the six labour hours of idle time, but not the reason, the sequence of events, or the PM notification log you need for a compensation event.

What Each Document Actually Contains

The Site Diary

The site diary captures events, conditions, and communications. Its content is primarily qualitative, although specific quantities appear where they're relevant to the narrative.

Typical entries cover:

• Weather conditions and how they affected operations (temperature, precipitation, wind for exposed structures)
• Work activities in progress: what was under way, what section of the works, whether it was proceeding as planned
• Labour and plant attendance, usually as a summary count rather than a detailed breakdown
• Instructions received: verbal or written directions from the Project Manager, Supervisor, or client representatives
• Delay events and their causes: utility clashes, design holds, late information, access restrictions
• Subcontractor attendance and performance where relevant
• Visitors to site, including client representatives and inspectors
• Safety and environmental incidents
• Any event that might become a compensation event under NEC4

The what to include in a site diary page covers this in full.

The Allocation Sheet

The allocation sheet captures resource deployment against activities. Its content is primarily quantitative: hours, quantities, codes.

Typical entries cover:

• Each operative by name or trade, the hours they worked, and the activity they were allocated to
• Each piece of plant, whether working or standing, and its activity allocation
• Materials received or consumed, tied to an activity reference
• Subcontractor resources, broken down by the same categories
• Any unproductive or standing time, with a reason code
• Daily output against the activity (metres poured, m3 excavated, linear metres of cable pulled)

The key feature is the activity reference. Every line on an allocation sheet should tie back to a specific activity in the programme or contract bill. That's what makes it commercially useful. Without activity codes, you have a payroll record. With them, you have the foundation for cost performance analysis.

When You Need Each One

This is the question most teams get wrong. It's not "diary or allocation sheet?" It's about which document takes precedence depending on what you're trying to prove or manage.

The pattern should be clear. Dispute or notification work starts with the site diary. Commercial quantification work starts with the allocation sheet.

The NEC4 Dimension

Under NEC4, both documents perform specific contractual functions. This is where teams who treat either document casually get hurt.

The site diary is your primary evidence base for compensation event notification. Under clause 61.3, the Contractor has 8 weeks from the date they became aware of a compensation event to notify the Project Manager. If your diary doesn't record when you first became aware of an event (a utility strike, a design hold, an instruction to proceed with a temporary works solution), you can't establish your awareness date. Miss the 8-week window and the CE is time-barred, regardless of its value. The NEC4 eight-week time bar page explains this in detail.

The allocation sheet is your primary evidence base for compensation event assessment. Under clause 63, the assessment is based on the effect on Defined Cost and the Accepted Programme. To demonstrate the effect on Defined Cost, you need to show what resources were planned for the activity and what resources were actually consumed or disrupted following the event. That data comes from allocation sheets, not diary entries.

Without both documents working in tandem, your NEC4 commercial management has a structural weakness. The diary gets you to the notification. The allocation sheet gets you to the money.

If you want to understand how these documents feed into your compensation event process in more depth, the site diary and NEC4 compensation events bridge page is the right next read.

Common Mistakes in How Teams Use These Documents

Using the diary as the allocation sheet. Some site managers write "8 guys on excavation, 2 on rebar, 1 plant operator, 360 and 8t vibro" in their diary entry and call it done. That's a summary, not an allocation sheet. There's no activity code, no hours breakdown, no link to the programme. When you're trying to demonstrate that the 360 was standing for 4 hours because of a late permit, a narrative summary won't cut it.

Treating the allocation sheet as optional on lump sum contracts. Even on NEC4 Option A (priced contract with activity schedule), allocation sheets matter. The mechanism for pricing compensation events is the same: Defined Cost is the standard. The Schedule of Cost Components still applies to CE assessments. Teams on Option A frequently under-resource their allocation process because they think it's only relevant for Option C. It's not.

Not keeping them in sync. The diary says there was a 3-hour delay to the formwork gang on 2 June 2025 due to a late concrete delivery. The allocation sheet for that day shows the formwork gang as fully productive. Now you have two documents that contradict each other. In adjudication, that's worse than having no records at all, because it raises questions about the reliability of everything else.

Retrospective allocation sheets. I've said this elsewhere and I'll say it again here. Allocation sheets completed from memory days or weeks after the fact are effectively useless for commercial defence. They might satisfy a basic audit. They won't survive scrutiny on a disputed claim.

Quick Reference: Which Document, Which Purpose