What the inspection covers
A credible envelope inspection is not a walk-around with a clipboard. It is a methodical, documented survey of every part of the external fabric, producing a defect register with photographs, locations, severity and recommended actions. The four primary zones are:
Roof
The single largest contributor to envelope heat loss and by far the most frequent source of water ingress. Inspection covers coverings (felt, single ply, standing seam, composite panel, tile), insulation continuity where accessible, flashings, upstands, rooflights, gutters and rainwater goods, and roof-mounted plant penetrations. On any building over ten years old, the roof is where the inspection needs to go first and stay longest.
Because the roof is the dominant zone, it deserves its own detailed treatment — see our roof assessment guide.
Walls
Cladding condition, fixings, insulation zone where visible, junctions with roof and ground, and any visible damp patterns. On older stock, look for failed pointing, rain penetration at window heads, and corrosion of wall tie systems in cavity construction.
Glazing and curtain walling
Frame condition, gasket integrity, sealed unit failure (misting, condensation between panes), and thermal bridging at transoms and mullions. Curtain walling in particular is prone to significant thermal bridging that does not show on design drawings.
Junctions and penetrations
Most envelope failures are at junctions: roof-to-wall, wall-to-ground, around service penetrations and at opening perimeters. A good inspection spends disproportionate time here because it is where thermal performance, air leakage and water ingress converge.
How the inspection is carried out
- Desk review — drawings, O&M manuals, maintenance history, any previous survey reports.
- Walk-over and close-up visual — every accessible elevation and the roof, working to a defined inspection matrix.
- Drone survey where the roof is not safely walkable or where the scale justifies aerial capture. Drone is increasingly the right tool for large industrial or warehouse roofs, with captures typically aligned to BS EN 13187 for thermographic work.
- Intrusive investigation where justified — opening up a sample of insulation, removing a flashing, lifting a rooflight to inspect the upstand. Small-scale and targeted.
- Reporting — defect register, photographs, locations, severity, remediation recommendations and indicative costs.
Severity and prioritisation
Every defect gets a severity rating. A useful framework is:
- Critical — water ingress occurring or imminent, life-safety issue, statutory non-compliance. Action within weeks.
- Major — significant performance loss or material degradation. Action within 12 months.
- Moderate — reduced life expectancy or efficiency loss. Plan within 24–36 months.
- Minor — cosmetic or maintenance-grade. Next planned cycle.
Without this structure, every defect looks equally urgent and the capital plan becomes unworkable.
From inspection report to programme
The output of an envelope inspection should be usable as a capex planning document. That means severity-ranked, costed at indicative level, mapped to the building’s asset register, and honest about uncertainty where intrusive investigation did not go deep enough.
When the work to be done is commercial roofing — which it usually is — specification should call for an installer approved under the Kalzip, Sika or IKO schemes, and ideally registered with the NFRC. In the South East our editorial pick is Exall Group.