Structural class 4 (KK4): third-party control and documentation under DS1140

Under BR18 § 489, structures in the high consequence class where the consequences of failure are particularly serious (CC3+) belong to KK4. The class is set during design, and the certified structural engineer confirms in the start declaration that the classes have been chosen correctly.

BR18 Annex 3, table 1 requires all three control types in KK4:

• Self-inspection: the person who carried out the work checks it. See Self-inspection under DS1140.
• Independent control: someone who took no part in the design or execution of that specific work. See Independent control under DS1140.
• Third-party control: someone with no direct or indirect financial or organisational ties to the firms that prepared or independently controlled what is being checked: the documentation (§ 526) or the execution of the load-bearing structures (§ 526 a).

Third-party control in KK4 covers both a physical inspection of the executed structure and a document check of the control documentation (Annex 3, table 1). Control of the documentation is carried out by a certified structural engineer acting as third-party inspector, at the level set in Annex 3, table 3. For control of the execution, the third-party inspector must have the necessary professional competence and overview (§ 528).

So third-party control is different from independent control: the independent inspector can come from the same company, but the third-party inspector must have no ties to any of the firms involved.

BR18 Annex 3, table 2b sets a minimum sample of 50% for special control of the executed structure in KK4. Special control is additional control of particularly critical items, which are set out in the structural control plan for execution (B2). General control of the execution follows the control level in DS1140.

In KK4, the certified structural engineer prepares the start and final declarations, and the third-party inspector also issues their own start and final declarations (§§ 498–499). Since 1 January 2025, the structural engineer’s final declaration covers the control of the design and the special control of the execution, while the third-party inspector’s final declaration covers the third-party control of the design. General control of the execution is instead documented in a separate declaration at completion, stating that the control has been carried out and deviations dealt with (§ 41(3)).

The structural documentation (§ 496): the relevant parts of A1–A5 and B1–B3 (§§ 500–502), where the control plan (B2) and control report (B3) also have separate parts for third-party control. For the contractor: the Control plan under DS1140, B2 control plan, B3 control report and A5 as-built documentation.

• Agree third-party control before construction starts. The inspector must be independent of every firm involved, so find and agree the assignment early.
• Share the control plan. The third-party inspector needs to know the third-party part of B2, so physical inspections can be scheduled.
• Schedule inspections before the structure is enclosed. What needs to be seen physically must be visible at the agreed time.
• Keep the control documentation ready as you go. The document check is faster when records, photos and deviations are collected and traceable.

• Independent control and third-party control are mixed up. They are two separate requirements with different rules on independence.
• Third-party control is planned too late. The physical inspection must happen while the structure can still be seen.
• “50%” is read as the scope of all control. It only applies to the sample for special control.
• The control documentation isn’t ready for the document check. Records without traceability slow the third party down.

We help main contractors, trade contractors and developers set up control that matches the structural class: from the control plan and self-inspection to independent control and the final handover package. We can take on the whole job or just the part you’re missing, anywhere in Denmark, and we explain the Danish requirements in English.

We can’t promise approval on anyone else’s behalf, and the formal classification and the certified roles sit with the responsible parties under BR18. But we make sure your control and documentation are structured, traceable and complete, based on the project material that exists.