What is a pre-plasterboard inspection?

It is the building control visit that happens when the structure is complete but before plasterboard, insulation, or boxing conceals anything. Councils also call it the structural, superstructure, or first fix inspection. It is the last chance to verify steels, wall ties, and roof timbers before they are hidden.

What happens if my builder covers up the structure before the BCO inspects it?

The building control officer cannot sign off what they cannot see, so they can require the concealing work to be stripped back and exposed again. That means removing plasterboard and insulation at your cost, which is one of the most expensive avoidable mistakes on an extension.

Who is responsible for booking building control inspections?

The legal duty to notify building control that a stage is ready sits with the person carrying out the work, which is usually your builder. But as the building owner you carry the ultimate liability if a stage is skipped, so on a self-managed build make sure the inspection actually happens rather than assuming the builder has booked it. Builders who skip the structural inspection create the costliest remediation scenario in the whole project.

How long does a building control structural inspection take?

Usually 20 to 40 minutes on site. The officer walks the structure, measures bearing lengths, looks into the cavity for wall ties, checks straps and insulation, and compares what is built against the approved drawings.

Does the structural inspection cost extra?

No. Your building control fee, paid when you submitted the application, covers every inspection across the project with no per-visit charge. The only indirect costs come from anything the officer finds that needs correcting.

Is local authority building control better than a private approved inspector?

For most domestic extensions, local authority building control is the safer choice. It costs the same, carries no insolvency risk, and brings local ground knowledge. Private approvers give more continuity with a named individual but lack enforcement powers.

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Phase 4 · Structure · Task 08 of 09

Building Control Inspection: Structure

What the BCO checks at the structural stage of your extension: steels, wall ties, cavity barriers, roof timbers, and the pre-plasterboard inspection that catches problems before they're hidden forever.

17 min readUpdated 2026Premium

Process infographic showing the building control structural inspection sequence: steels checked, wall ties verified, roof timbers inspected, cavity barriers confirmed, and pre-plasterboard sign-off given before any work is concealed

Prerequisites

Complete these first

Cover up your steelwork, wall ties, or roof structure before the building control officer has inspected them and you've created the most expensive kind of mistake: the kind where finished work gets ripped off the walls. Plasterboard stripped. Insulation pulled out. Weeks of progress reversed so an inspector can see what should have been visible when they visited. Forum after forum describes the same pattern: builder skips the structural inspection, work gets covered, the BCO can't sign off what they can't see.

The structural stage inspection is the last time anyone will see the bones of your extension. After this, plasterboard, insulation, and plaster conceal everything. Wall ties, cavity barriers, holding-down straps, steel bearing lengths, insulation depth, fire stopping. All of it gets buried. If the BCO hasn't verified it before it's concealed, it either gets exposed again (at your cost) or it never gets checked at all.

Do this first

Before the BCO can carry out the structural inspection, all the major structural work must be complete and visible. Your walls must be at plate height with wall ties in place. Your structural steels must be installed with padstones, and any design changes notified to building control. Your roof structure must be framed with the wall plate strapped. The roof covering can be on (some BCOs combine the structural and covering inspections), but the internal side of the structure must remain exposed. No plasterboard. No boarding. No boxing-in of steels.

This is a single inspection covering the whole superstructure at once: the walls up to plate height, the steels, and the roof timbers. It is not a separate wall visit and roof visit. Everything structural has to be up, and still visible from inside, at the same time.

What this guide covers

01This Is the Pre-Plasterboard Inspection
02What the BCO Actually Checks
03Notifying Building Control of Design Changes
04Booking the Inspection
05Preparing for the Visit
06What Happens When the BCO Finds Something
07The Cost of This Inspection
08LABC vs Private RBCA
09Multiple BCOs on the Same Project
10The BCO Is Your Ally
11What Comes After This Inspection

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