A facilities manager recently explained their approach to planned preventive maintenance inspections: “We try to keep it as lean as possible. We use window cleaners — they are up there anyway.”
It is a common position. On the face of it, it makes commercial sense. Biannual inspections are a cost. If someone is already on the roof, why not tick the box?
Here is why that logic fails — and why the consequences of it are becoming harder to ignore.
The box does not get ticked
Roof guarantee conditions — from manufacturers and from the NHBC — typically require biannual inspections by competent persons. That is not aspirational language. It is contractual.
If you try to claim on a guarantee and produce a report from an inspector who is not competent in roof waterproofing, the guarantee provider can decline to honour it. The biannual inspection happened. The report exists. But the competence was not there — and the guarantee does not hold.
The tick-box exercise that was meant to protect the building actually provides no protection at all.
The Building Safety Act has changed the position
Since April 2024, the Building Safety Act 2022 is fully in force. At its heart is a legal duty: anyone carrying out work on a building must be competent for that role. Competence is defined as having the relevant knowledge, skills, experience, and behaviours.
That applies to inspectors. A window cleaner checking a roof waterproofing system does not meet that definition. It is not about willingness or effort — it is about whether they have the knowledge base to identify what is wrong. The Act creates legal liability for duty holders who appoint incompetent parties.
What a competent inspector actually looks for
We looked at a project in Greenwich. The regular inspection reports had been filed for years. The inspector was going up, walking around, writing a report. Nobody doubted that.
When we got on the roof, we found large splits in the membrane — visible in the photos from their own reports, if you had known what you were looking at. Then we looked at areas they had not checked. More defects. Then the roofer who was on site doing repairs had not found them either.
Three parties had been on that roof. None had found what someone with genuine waterproofing expertise found in a single visit.
This is not unusual. Roofs are complex systems. The failure is not always where the water appears. Terminations, upstands, penetrations, counter flashings — these are the areas of systematic weakness, and they require systematic knowledge to inspect properly.
What are you looking for in a competent inspector?
- NVQ Level 3 in waterproofing inspection, or equivalent qualification
- A demonstrable CV of relevant roofing and waterproofing experience
- RAWTA membership — rawta.org — the clearest indicator that someone has the technical knowledge to test and inspect waterproofing systems properly
- Reports that would withstand scrutiny if a guarantee claim was made
What good PPM looks like
The difference between a competent biannual inspection and an incompetent one is not primarily about cost. It is about what happens next.
A competent inspection identifies problems while they are still small: a sealant that needs replacing, an upstand that has started to move, an outlet that is partially blocked and creating standing water. Deal with those in time and you are spending hundreds, not tens of thousands.
An incompetent inspection misses them. The leak develops. The insulation saturates. By the time the symptom is visible internally, the remediation is a different order of magnitude entirely.
We never trust previous repairs until we have checked them ourselves. It is not because roofers are incompetent. It is because the person doing the repair does not always have the same view of the whole system as someone whose sole purpose is investigation and inspection.
Sensors change the equation
Biannual inspections remain a requirement under BS 6229:2025 and most manufacturer guarantee conditions. But they are a point-in-time snapshot. A roof that passes inspection in October can start failing in February. Without a continuous monitoring system, that failure develops in the dark.
Vector’s permanent sensor monitoring — using Norwegian Sensor Innovation technology embedded during construction — provides 24/7 real-time monitoring between inspections. If moisture enters the system, an automated alert triggers. The biannual inspection then becomes a verification exercise rather than a discovery exercise. The two work together.
Talk to us about biannual PPM inspections | Permanent sensor monitoring