The construction site diary as evidence: missing entries are hard to prove years later

When a construction project ends up in court, both parties bring piles of documents prepared later. The court looks for records made when events actually happened. The construction site diary is often the only such document. Construction Act No. 25/2025 Coll. established clear rules, which construction contracts should develop further. Whether the diary helps or harms a party in a dispute is determined long beforehand, through everyday entries.

Who keeps the diary and who may make entries

Keeping the diary is a statutory duty of the site manager, who organises, directs and supervises construction work (section 37(1) of Act No. 25/2025 Coll.):

Unofficial English translation: The site manager must keep a construction site diary for the project. The diary must be available from the site manager for entries and inspection from the first day the construction site is established until the day the completed construction is handed over.

— Section 39(1) of Act No. 25/2025 Coll.

The site manager is not the only person entitled to make entries. The statutory list includes the developer and building owner, lead designer and designers of individual documentation sections, construction supervisor, surveyor, state construction inspectors and others (section 39(2)). The contractor must also record agreed departures from the verified construction design (section 32(3)). The diary is therefore a shared record for those responsible for the project, rather than the contractor’s private notebook.

Why the diary often determines a dispute

A typical construction dispute turns on events months earlier: when a design change arrived, who stopped work and whether the contractor warned that the supplied material was unsuitable. Witness memories fade and emails are fragmented. A dated entry made on site comes closest to an objective account. Record obstacles and their duration, changes to design documents and instructions, work suspensions and reasons, and warnings issued by the contractor to the client.

The last category has direct statutory significance. The Commercial Code (Act No. 513/1991 Coll.) makes relief from liability for defects dependent on a demonstrable warning:

Unofficial English translation: The contractor must, without undue delay, warn the client that items received from the client or instructions given by the client for carrying out the work are unsuitable, if the contractor could have identified that unsuitability by exercising professional care.

— Section 551(1) of the Commercial Code

The diary is a natural place to record the warning and any written insistence by the client on its instructions. Our advice on defects arising from the client’s instructions explains the liability consequences. The same logic applies to obstacles: a contractor who fails formally to suspend work and document obstacles attributable to the client bears the consequences of delay. That was the contractor’s problem in case 5Obdo/75/2019, which ended with the Slovak Supreme Court rejecting its appeal on points of law. The contractual delay penalty set off against the contractor’s claim consumed the entire outstanding contract price.

Entries can also be used against their author

The diary serves both parties. Missing events are hard to prove years later, while recorded statements can be used against the person who made them. A contractor’s entry that work is progressing without obstacles can undermine its delay defence just as much as an omitted obstacle. The diary also has limits: it records progress and is not itself a legal act. Handover is a separate step documented in a handover report; entries alone do not replace it. Our advice on an unsigned handover report considers work already in use without a signed report.

Include diary procedures in the contract

The law determines who keeps the diary and who can make entries; the contract shapes its effect between the parties. A construction contract should identify who confirms entries for the client, set a deadline for objections and provide that unchallenged entries are deemed accepted. It should also address the client’s access and require photographic evidence of significant events. These arrangements discipline both parties and make the diary a reliable shared record.

How we can help

We establish diary procedures in the construction contract. Our legal support for construction companies helps maintain consistent records during projects. In existing disputes, the diary becomes central to evidence for our litigation representation. Smaller projects have their own rules, discussed in our advice on a returned minor construction notification. Reviewing diary clauses before work starts is easier than reconstructing events years later in court.