Plenty of commercial property managers find out they have an asbestos cement roof the same way — a quote for general roof cleaning comes back with an awkward footnote: "We don't touch asbestos." If you're now working out what should actually happen, and who should be doing it, this article covers the full process: what responsible contractors do, why each step matters legally and practically, and what to ask before anyone gets on your roof.

Asbestos cement isn't the same as loose asbestos — but it's still regulated

Most commercial roofs containing asbestos are built from *asbestos cement (AC) sheet* — the corrugated grey sheeting common to warehouses, agricultural buildings, and industrial units put up between the 1950s and 1980s. In AC, asbestos fibres are bound within a cement matrix. That's structurally different from the loose, friable lagging associated with the worst asbestos hazards.

In practice, professional cleaning of asbestos cement usually falls under *non-licensed asbestos work* as defined by the Control of Asbestos Regulations 2012 (CAR 2012). An HSE licence for the work itself isn't typically required, provided the sheets are in reasonable condition and the cleaning method is low-risk. But "non-licensed" doesn't mean unregulated. Operatives must hold specific non-licensed asbestos training. A written risk assessment and method statement are mandatory. And under Regulation 4 of CAR 2012, you as the dutyholder — building owner or facilities manager — have a legal obligation to manage asbestos on your premises, which includes providing roof survey information to any contractor before work starts.

Where sheet condition is poor or the work is more intrusive, it may escalate to *notifiable non-licensed work (NNLW)* , triggering additional requirements: notification to the enforcing authority, medical records for workers, and formal exposure logs. A competent contractor will tell you which category applies before pricing the job.

The cleaning process: slow, wet, and deliberately gentle

Professional asbestos cement roof cleaning isn't about pressure and power — it's the opposite.

The process follows a defined sequence:

1. Site survey and condition assessment. Before any work begins, the contractor should inspect the roof against HSG264-compliant survey data. They're looking at sheet condition — cracking, delamination, broken fixings — along with access requirements and anything that affects the risk level. If no current asbestos survey exists, commission one first.
2. Biocide application.  A specialist biocide is applied by low-pressure sprayer to kill moss, algae, lichen, and other biological growth, then left to dwell — typically several days. This is the critical step. The point is to let the chemistry do the work, which reduces or eliminates the need for physical scrubbing. Scrubbing is where fibre release risk rises sharply.
3. Low-pressure washing and soft mechanical cleaning.  Once the biocide has done its job, the roof is cleaned using low-pressure water. The HSE's Asbestos Essentials task sheet A12 , which covers cleaning weathered AC roofing and cladding, is explicit: *no high-pressure washing*. High-pressure jetting can destroy the surface structure of asbestos cement, generating contaminated slurry and significantly increasing fibre counts. Where manual agitation is needed, plastic scrapers and soft brushes are used — never metal tools that could bite into the surface.
4. Debris capture.  Before water and debris can reach gutters and drains, the work area should be managed to contain the slurry. HSE guidance requires contaminated material to be collected, not dispersed.

Workers in the cleaning zone wear FFP3 disposable respirators, disposable hooded overalls, and laceless boots throughout. The fact that a respirator isn't normally required for an operator positioned well away from the cleaning machine tells you something about how carefully the work zones need to be defined.

Runoff control and waste disposal

This is where cheaper contractors cut corners — and where you face the most direct legal exposure if things go wrong.

All water and debris from an asbestos cement roof cleaning job is, legally, *asbestos-contaminated waste*. That includes contaminated rinse water, used rags, disposable PPE, polythene sheeting used to protect building entry points, and any other waste generated on site. Under Regulation 24 of CAR 2012 and the Hazardous Waste Regulations 2005,  this waste must be:

• Double-bagged or double-wrapped in sealed polythene, with correct asbestos hazard labelling — standard practice is a red inner bag with asbestos warnings and a clear outer bag with hazard markings
• Transported only by a registered waste carrier — registered with the Environment Agency in England, Natural Resources Wales, or SEPA in Scotland
• Accompanied by a Hazardous Waste Consignment Note (or Special Waste consignment note in Scotland) for every load
• Disposed of only at a facility licensed to accept asbestos — in practice, licensed hazardous waste landfill, as there are no legal UK options for incineration or alternative treatment

Records of waste disposal — carrier details, quantities, disposal site, consignment notes — must be retained for a minimum of two years. Most compliance advisors recommend three.

A contractor who can't clearly explain how they'll handle contaminated runoff and dispose of waste materials is not a contractor you should use. Ask the question directly, and ask to see the paperwork after the job is complete.

After cleaning: when encapsulation makes financial sense

Cleaning removes biological growth and restores the roof's appearance. It doesn't address the longer-term question: how long will these sheets last, and what's the most cost-effective way to protect them?

If the cleaned sheets are structurally sound — not extensively cracked, delaminating, or showing failed fixings — *encapsulation* is worth understanding. In the context of asbestos cement roofing, encapsulation means applying a specialist coating that bonds to the surface, physically locks fibres in place, and restores weatherproofing.

Several system types exist. High-build *elastomeric polymer coatings* are applied in multiple layers and can, according to ARCA's published guidance on encapsulation, provide up to 20 years of protection if undisturbed. *Spray-applied polyurethane foam systems* at a minimum 25mm thickness create a seamless waterproof deck across the entire roof surface, with some providers offering 20-year warranties. *Liquid rubber spray systems* at the premium end carry 25-year warranties and are cited as delivering around 60% cost savings compared to full re-roofing.

Encapsulation is not appropriate for seriously degraded sheets. ARCA is clear: encapsulation should only be considered where the ACM is firmly adhering to the substrate and is in a viable state. If sheets are badly spalled, cracked across multiple panels, or showing significant structural deterioration, you're looking at replacement — a different, higher-cost conversation involving licensed removal and hazardous waste disposal at scale.

For a warehouse, logistics facility, or agricultural building with weathered but intact sheets, encapsulation can extend the roof's serviceable life by 15–25 years while satisfying the CAR 2012 duty to manage asbestos in situ. Any encapsulated areas must remain on your asbestos management plan and be re-inspected at least annually.

Choosing a contractor: what to ask for

Most property managers assume any roofer or exterior cleaning company can handle an asbestos cement roof. They can't. A genuinely compliant contractor should be able to provide all of the following before you agree to anything:

• Evidence of non-licensed asbestos training (Category B level minimum) for operatives who will work directly on the roof surface. Asbestos awareness training alone is not sufficient for hands-on AC cleaning work.
• A detailed written method statement covering site preparation, access, cleaning method, biocide products, dust and fibre suppression, RPE and PPE specification, runoff and debris control, waste packaging and disposal route, and emergency procedures.
• Confirmation of which waste carrier they use,  including their Environment Agency, SEPA, or NRW registration number — you can verify this yourself at the relevant public register.
• Public liability insurance that explicitly covers asbestos work.  Many standard contractor policies exclude it. Check the certificate, not just the summary.
• References from comparable commercial projects — similar building type, scale, and asbestos cement coverage.

The red flags are straightforward. Any contractor offering high-pressure washing on an asbestos roof is either unaware of HSE guidance or willing to ignore it — the HSE has been unambiguous that high-pressure water jetting on asbestos cement is prohibited. Reluctance to discuss waste disposal, inability to produce a written method statement, or vague answers about training are all reasons to look elsewhere.

What to prepare before the job — and capture after

Before the job:

• Confirm you have an up-to-date HSG264-compliant asbestos survey covering the roof, and share it with the contractor
• Confirm access arrangements and notify relevant tenants or building users of the work schedule
• Obtain and file the contractor's method statement and insurance documents before work begins
• Agree on how runoff and perimeter areas will be managed, particularly near drainage

After the job:

• Obtain signed copies of all hazardous waste consignment notes — these are your legal proof of compliant disposal
• Request photographic evidence of the cleaned and, if applicable, coated roof
• Get any coating or encapsulation warranties in writing, with manufacturer references
• Update your asbestos management plan to reflect the work completed and current condition of the roof

A complete maintenance record demonstrates diligence to your insurers, satisfies CAR 2012 duty-to-manage obligations, and makes commercial due diligence considerably simpler if you ever sell or refinance the property.

Where to start

1. Check whether you have a current asbestos survey covering your roof. If not, commission a management survey (HSG264-compliant) before approaching any cleaning contractor — you need it, and so do they.
2. Contact two or three specialist commercial asbestos roof cleaning contractors — not general exterior cleaners — and request written method statements, training evidence, and waste carrier details from each.
3. Verify waste carrier registrations at the Environment Agency's public register before agreeing to anything.
4. Review your asbestos management plan  to confirm the roof is included, and flag the planned cleaning work to whoever maintains it.
   

The bottom line

Asbestos cement roofing can be safely cleaned and maintained — but only by contractors who understand what they're working with, follow HSE guidance without shortcuts, and treat the waste they generate as the hazardous material it legally is. The process is slower and more considered than standard roof washing, and the paperwork trail after the job matters as much as the work itself. Before anyone quotes you a price, ask how they handle the runoff. The answer will tell you most of what you need to know.

Does your current asbestos management plan include enough detail on the roof to hand to a contractor tomorrow — or is that the first thing that needs updating?