How to Gain a Building Assessment Certificate: A Structural Perspective

We've spent a significant amount of time reviewing Building Safety Regulator (BSR) feedback on the structural elements of Safety Case Reports submitted as part of Building Assessment Certificate (BAC) applications. That experience — seeing what gets challenged, what gets accepted without question, and what comes back with further information requests — has shaped a general approach we use to help clients get a Higher Risk Building's structural evidence to the standard the BSR expects.

It's worth being upfront about one thing first: the BSR's approach isn't perfectly uniform. How much weight a particular case officer places on a given gap can vary from one reviewer to another, and from one building to the next. What follows isn't a fixed checklist — it's the general approach we've found works, set out in line with the Institution of Structural Engineers' guidance, Preparing Safety Case Reports for Higher-Risk Buildings Under the Building Safety Act: Guidance for Structural Engineers.

Modern Buildings

The Design Information Gap

A large proportion of the structural issues raised against modern buildings come down to one thing: a lack of structural design information — calculations, drawings, and specifications — that can actually demonstrate compliance. Collecting this information, wherever it still exists, should be treated as a priority. And where it genuinely can't be recovered, it's just as important to be able to show the BSR that a proper attempt was made to find it, rather than simply presenting a gap with nothing behind it.

Calculations That Miss the Critical Risk Scenarios

In other cases, the structural calculations exist — but they don't cover the risk scenarios that actually matter for a BAC: vehicle impact, accidental explosion, and fire-induced structural damage, in particular. This is one of the more difficult issues to manage, because it tends to surface late. Principal Accountable Persons and property managers reasonably assume that if calculations exist at all, everything the BSR needs has already been given to the Regulator and to their structural engineer. In our experience, that's commonly not the case.

Structural Condition Is a Secondary Concern — But Not an Absent One

For a modern building, the general condition of the structure tends to carry less weight in the BSR's review than it does for an older one — there simply hasn't been time for significant deterioration. That doesn't remove the need for an inspection. A structural engineer still needs to visit and confirm that the building was actually constructed, and is performing, to a standard consistent with its design intent. Construction quality issues do get picked up this way, even on relatively new buildings.

Where the Real Focus Sits: Accidental Design Situations

For modern buildings, the main area of BSR scrutiny is accidental design situations — fire, accidental explosion, and vehicle impact. These are, by nature, scenarios that can't be proven through experience: a building that has never been hit by a vehicle or exposed to an explosion hasn't demonstrated it would survive one, it's simply never been tested. That's exactly why the BSR pushes hard on this point, and why it needs to be answered through calculation and robustness demonstration, not asserted from a clean incident history.

Transfer Slabs: A Priority Item

Where a building has a transfer slab, it warrants closer attention than the rest of the structure. Design and assessment practice for transfer slabs — particularly around punching shear — has not historically kept pace with the risk, a concern serious enough that the Building Safety Regulator wrote directly to Principal Accountable Persons and building owners about it. IStructE has since issued its own updated guidance on the design and assessment of transfer slabs to help close that gap. If your building has one, treat it as a standing item on the structural assessment, not an afterthought.

Historic Buildings

The general shape of the approach for historic buildings is similar to modern ones, but the emphasis shifts in a few important ways. Foundation design and general structural design calculations, for instance, tend to carry less weight in the review of a historic building than they do for a modern one — decades of proven, in-service performance are reasonable evidence that the building can carry its normal, day-to-day loading, in a way a modern building simply doesn't have yet. That evidence only covers normal loading, though, which is exactly why the accidental design situations below remain the real priority.

Disproportionate Collapse Is the Headline Risk

We put heightened focus on whether a historic building's structure might be deficient in disproportionate collapse resistance — its ability to avoid a collapse disproportionate to its original cause. This matters most for buildings constructed before around 1970, before robustness requirements were introduced into the Building Regulations in the wake of the Ronan Point collapse. A building from that era was very likely never designed with these accidental load cases in mind at all, which makes this the single highest-priority item on a historic building's structural review.

Fire and Vehicle Impact Matter Just as Much

Disproportionate collapse doesn't sit in isolation — fire and vehicle impact deserve just as much attention, for the same reason as with modern buildings: a long service history proves nothing about how a structure would perform under an event it has never actually experienced. For reinforced concrete buildings in particular, fire is where this becomes a real and often overlooked evidence gap. A concrete element's fire resistance depends heavily on the depth of cover protecting its reinforcement, and older buildings were frequently built to cover standards below today's expectations — cover that can also have reduced further over time through carbonation and general deterioration. Where the as-built cover can't be confirmed from records, a cover survey — measuring actual cover on site with a covermeter, backed by targeted exposure where needed — becomes critical evidence, because it's often the only reliable way to establish whether the structure's real fire resistance matches what was originally intended.

Condition Comes First

Unlike with modern buildings, the condition of the structure is central to a historic building's assessment. A visit by a structural engineer — a proper, hands-on condition inspection — is one of the most important pieces of evidence available, and it's where we'd start.

Design Information Still Matters, Where It Exists

Proof of the original structural design remains valuable evidence, even for an older building, and it's still worth pursuing wherever there's a realistic chance of finding it.

Focused Assessments

Because of all this, focused assessments — targeted at the specific areas a condition survey flags as uncertain, rather than a full, exhaustive re-assessment of the entire structure — tend to be the most effective way to close the remaining gaps on a historic building.

Frequently Asked Questions