NHBC inspections on apartments and blocks

Why blocks are inspected differently

A house is a single, self-contained unit and the inspection sequence follows it from the ground up. A block is dozens of units sharing a structure, a fire strategy, an acoustic strategy and a set of risers. The inspection risk moves from the individual dwelling to the interfaces between them.

That changes the shape of the Bespoke Technical Risk Management Plan. Expect more Risk Based Inspections concentrated on compartmentation, fire stopping, separating construction and the sequencing of trades through risers and corridors — the places where three subcontractors work on the same penetration.

It also changes the record keeping. Every unit needs its own inspection record and its own evidence, even where the construction is identical, because each unit gets its own warranty.

Compartmentation and fire stopping

This is the single highest-risk area on a block and the one that generates the most severe Reportable Items. Compartmentation only works if it is continuous, and it is broken by every service that crosses it — which is most of them.

The practical problem is sequencing. A penetration is often made by one trade, used by a second, and fire stopped by a third, sometimes weeks apart. If nobody owns the closing-out of each penetration, the block ends up with a scatter of untreated holes that are extremely expensive to find and prove after the ceilings go in.

• Number every riser and compartment penetration and track it to a closed state.
• Photograph each fire stopped penetration with the location identifiable, before it is boarded.
• Use the specified system and record the product — mixed sealants and unbranded foam get written up.
• Check cavity barriers at compartment lines and around every window and door opening.
• Do not let a follow-on trade re-penetrate a completed fire stop without re-treating it.
• Keep a fire stopping register per floor, signed off by the installer.

Separating walls, floors and sound testing

Separating construction has to meet Part E, either by pre-completion sound testing or by using Robust Details. Both routes are inspected, and both are unforgiving of small deviations — a rigid connection between leaves, a service chased into a separating wall, or a missed flanking detail can fail a whole floor.

Where Robust Details are registered, the inspector checks the construction matches the registered detail exactly. A deviation does not just produce an RI; it invalidates the registration and forces you into pre-completion testing you had not programmed.

Sound testing is done on a sample, but a failed sample condemns the units it represents. Get the first-of-type built carefully and inspected hard.

Communal areas, plant and the parts nobody owns

Corridors, cores, stairs, lift lobbies, bin and cycle stores, plant rooms and roof areas all form part of the inspected works, and they are habitually the last things finished because no individual unit handover depends on them — right up until the point every handover depends on them.

Communal areas also carry their own compliance load: emergency lighting, smoke ventilation, fire doors and signage, access and means of escape. These are inspected and they need commissioning evidence like anything else.

• Programme communal areas as their own plot with their own stage checks.
• Fire doors: check the door, the frame, the ironmongery and the gaps, and keep the certification.
• Smoke ventilation, sprinklers and emergency lighting all need commissioning records.
• Roof plant, walkways and edge protection are inspected and frequently forgotten.
• Lift installation and commissioning sits on the critical path for the first handover.

Per-unit records and phased handovers

Blocks are usually handed over in phases: a core, a floor, or a stack at a time. That means the pre-handover position has to be assessed per unit while the building around it is still a construction site.

Practically, that requires unit-level discipline. Each apartment needs its own key stage record, its own photographic evidence, its own commissioning certificates and its own closed-out RIs. A block-level folder is not enough — at the point of sale, a conveyancer is asking about one flat.

It also requires protection. Completed units on a floor still being worked cause more damage snags than anything else on a block, and damage found at pre-handover is your problem, not the trade’s.

Where blocks pick up the most Reportable Items

• Fire stopping missing or incomplete at riser and compartment penetrations.
• Cavity barriers omitted or discontinuous at compartment lines.
• Separating construction deviating from the registered Robust Detail.
• Services chased into separating walls, creating a flanking path.
• Balcony and terrace thresholds, falls and drainage detailing.
• Communal area compliance items left until after the first unit handovers.