DS1140 for contractors: who's responsible for what?

Self-inspection isn't the structural engineer's or the building owner's responsibility - it's the ongoing control the contractor carries out as work progresses, based on the control points and control level the B2 plan sets out.

In practice, that means the individual trade contractor - carpenter, bricklayer, concrete contractor or others - is responsible for checking their own work as it happens, not only once the work is finished and reviewed by others.

Without ongoing B3 documentation, no one - neither the structural engineer nor any independent inspector - can see whether self-inspection actually took place. That's why B3 typically becomes the place where poorly handled responsibility becomes visible, regardless of how good the actual craftsmanship is.

A contractor who did the work correctly but didn't document it is, in practice, in the same position as one who didn't check at all - because there's nothing to show the structural engineer.

The most common mistake is that several people on site share responsibility informally, with none of them holding the overall picture. This typically happens on larger sites with many trade contractors, where no single person naturally takes ownership of the combined B3 documentation.

When the B2 plan names a responsible person for each control point from the start, that situation is avoided, because it's clear who needs to deliver what - and who to ask if something is missing.

For each control point they're responsible for, the contractor is expected to carry out the control in accordance with the control type and control level the B2 plan specifies, and to document the result with date, executing party and a clear outcome - approved, or a described deviation.

It isn't enough to carry out the control correctly if it isn't also documented in a way the structural engineer can later follow. Documentation is as much a part of the task as the control work itself.

Several contractors can readily be responsible for their own control points, as long as the B2 plan clearly names who's responsible for what. What needs to be avoided is letting responsibility for the combined B3 documentation float freely between the parties without a fixed process for how individual contributions are gathered in one place.

On one site with three trade contractors - carpenter, bricklayer and plumber - it was unclear who was responsible for documenting the control of a connection where all three trades were involved. The result was that none of them documented the point adequately, because each party assumed another would handle it.

When the structural engineer reviewed the B3 report, they spotted the gap, and the case was delayed while the three parties had to agree on who had actually done what - a situation that could have been avoided if the B2 plan had named one responsible party for that specific point.

The most effective solution is to review the B2 plan together with all involved trade contractors before work begins, and agree concretely on who's responsible for each control point that involves more than one trade. It takes little time to clarify upfront, but can save significant time and disagreement later.

Inadequate self-inspection can matter if a dispute later arises over a building's quality. Without documentation that the control was actually carried out, it can be hard for the contractor to prove the work was done in accordance with the requirements - even if it was in fact done correctly.

That's another reason documentation shouldn't be seen as an administrative formality, but as part of the protection the contractor has for themselves if a disagreement arises later.

On sites with staff turnover, it makes sense to have a fixed routine for how new employees are introduced to which control points they're responsible for, and how the documentation needs to be carried out. Without it, you risk responsibility that was previously clearly assigned becoming unclear when a new person takes over a task partway through.

A short review of the relevant parts of the B2 plan when new employees join is a simple way to avoid this becoming a source of gaps in the B3 report later.

Responsibility for carrying out and documenting control isn't necessarily the same as responsibility for the construction work itself - a foreman might, for example, hold overall responsibility for the control documentation, even though a different worker carries out the physical work. That distinction should be clearly stated in the B2 plan, so there's no doubt about who is actually accountable if a control point is missing.

If seasonal or temporary staff are used for parts of the construction, it's especially important to ensure a short, clear introduction to the documentation requirement before they start on site, rather than assuming it will be picked up along the way. This group is statistically more likely to leave gaps in the documentation, simply because they have less time to learn the process.

Where work is carried out as piecework, with several workers sharing a combined task, it's especially important to name who is responsible for documenting control of each point, rather than assuming 'the team' will take care of it. Piecework tends in practice to make the division of responsibility less clear, not more, unless it's explicitly agreed from the start.

If the foreman or the person responsible for control documentation changes partway through a project, the new person needs a concrete handover of how far the documentation has progressed and which points remain open - not just a general introduction to the project. Without that concrete handover, there's a real risk that already-completed controls get documented twice, or that some points fall between the cracks entirely.

Beyond the B2 plan's internal division of responsibility, it's a good idea to have the overall allocation of DS1140 responsibility set out in the construction contract itself, particularly where subcontractors are involved. That gives a clear, legally grounded starting point if doubt later arises over who was responsible for a particular documentation task.

At the end of a project, a short review of how responsibility for control documentation actually played out in practice pays off - where it worked smoothly, and where confusion arose. That review is cheap to do and often surfaces a small process fix that saves considerably more time on the next project than it costs to identify now.

If a subcontractor uses their own documentation system rather than the main contractor's, it pays to agree early exactly how their records will be folded into the overall B3 report, rather than discovering at handover that two incompatible formats need to be reconciled under time pressure.

If disputes about who was responsible for a given control point keep recurring across projects, it helps to review whether the underlying B2 plan template consistently assigns responsibility clearly enough, rather than treating each dispute as a one-off. A small wording fix at template level often resolves a pattern that would otherwise keep repeating project after project.