Overclad or strip an asbestos cement farm roof for solar

On a pre-2000 farm building the roof is usually the first thing an installer looks at and the last thing the owner wants to pay for. If the sheets are asbestos cement, the choice is rarely “panels or no panels”. It is between laying a new roof over the old sheets (overcladding), stripping them and starting again, or leaving the roof alone and putting the array somewhere else. This guide sets out what HSE and the roofing contractors’ trade body say about the first two, what changes when an array is going on the result, and what a quote should list. The legal position, and why neither option is compulsory, is on the main guide to solar panels on asbestos cement farm roofs.

The three options

Option	Tends to fit when	Pay attention to
Leave the roof, put the array on another roof or on the ground	The sheets are in good condition and nothing else needs doing to the building	The asbestos still has to be managed under the duty to manage; the array cannot be fixed through the sheets
Overclad	The structure can take the extra load, the sheets are intact, and the work can be done without breaking them	Every penetrating fixing is a disturbance of the material; twin-skin and liner constructions; who is working under the roof while it is done
Strip and re-roof	Purlins are degraded or overstressed, the sheets are breaking up, other asbestos materials are present, or the roof is at the end of its life anyway	Dust control, waste consignment, how the building is kept weathertight each day

Nothing here says one route is cheaper or safer in general. NFRC’s guidance says over-cladding may reduce disruption in some circumstances, but continued occupation should only be considered after a project-specific assessment of how much asbestos disturbance the fixings cause and how exposed the people inside are.

What HSE says (Asbestos Essentials sheet A14)

HSE’s task sheet A14, “Removing asbestos cement (AC) sheets, gutters etc and dismantling a small AC structure” (published 09/17), is written for non-licensed work. The points that matter for a farm roof:

• Overlaying is raised as an option. The sheet asks whether the sheets can be overlaid with non-asbestos material instead of removed. If so, the new material is attached to the existing purlins, and drilling through the asbestos cement is to be avoided; where it cannot be avoided, the separate drilling sheet (A9) applies.
• The roof is fragile. AC roofs are always fragile and cannot bear weight.
• Removal should not break the sheets. Avoid or minimise breaking the material. Large pieces are lowered, not dropped or put down a rubble chute; they are double-wrapped in 1000-gauge polythene, sealed with tape, labelled with asbestos warning stickers and put in a lockable skip.
• Breaking is the trigger. If the sheets break up and create significant dust, the work becomes notifiable non-licensed work, which is a different regime from the one the sheet describes.
• It stops at plain asbestos cement. The sheet is not appropriate where other asbestos-containing materials such as lagging or insulating board are present; HSE says to use an HSE-licensed contractor for those.
• Clearance sampling. Clearance air sampling is not normally required after this kind of work.

What NFRC adds (guidance sheet HSGS44)

NFRC, the National Federation of Roofing Contractors, publishes HSGS44, “Asbestos Cement Roof Sheets Removal and Over Cladding”, for contractors, designers and clients. It is the more detailed of the two on overcladding, and it covers four things a farm client rarely sees spelt out:

• Survey before anything else. A comprehensive survey of the roof, including testing for asbestos, the condition of the structure, sheets, roof lights and glazing, gutters, access, overhead power lines and ground conditions for cranes or hoists. It also asks for the existing construction to be understood: historic roofs may be twin-skin insulated systems, liner systems or spacer arrangements, not single-skin sheets.
• Structure first. A qualified structural engineer is to assess whether the existing structure can accept additional dead and live loading, whether the project strips or over-clads, with solar panels named among the loads the original frame may not have been designed for. If purlins, trusses or supports are degraded or overstressed, removal may be the only viable option. On concrete purlins with single-skin sheets nobody should drill into the purlin to fix a secondary member; the guidance describes a galvanised steel top hat fixed with J-bolts instead.
• Controls where fixings go through the sheets. The over-cladding fixings are drilled through the existing sheet and sometimes the liner. The guidance calls for project-specific asbestos risk assessments where fixings penetrate, notes that dust suppression should be one element of the control strategy and not assumed to remove fibre release, and lists controls such as self-drilling screws pre-coated with grease, wallpaper paste along the fixing line, pre-wetting or a diluted PVA solution, slow low-pressure drilling and immediate damp clean-up.
• Stripping, the paperwork and the people. Operatives are to hold Category B (non-licensable work) training under the Control of Asbestos Regulations 2012. Sheets are double-wrapped, labelled and placed in licensed, lockable skips, carried by a registered waste carrier and consigned on a Hazardous Waste Consignment Note. Air monitoring is not legally required for non-licensed work but is described as good practice, with a control limit of 0.1 fibres per cm3 over four hours. Underslung netting is the primary collective fall-prevention method under the Work at Height Regulations 2005, with over-netting acceptable only when higher controls have been ruled out.

What changes when panels are going on the result

• The new outer skin carries the array. Rails and brackets need a fixing position on the purlins or the new roof’s support system, not on old cement sheets. That is a design decision to make before the roofing contractor is chosen, not after.
• The loading check covers both layers. An overclad roof carries the old sheets, the new skin and the array. The module and racking weights and the building-control position are in the guide to solar panel weight and roof loading.
• The asbestos stays on the register. Overcladding covers the material and does not remove it. It still has to be recorded and managed, and whoever works on the roof later needs to know it is there.
• Timing the two jobs together. Doing the re-roof and the array as one project means one scaffold and one access arrangement. The sequencing is covered in the notes on farm solar and roof replacement timing and on combined re-roof plus solar.

What a quote for either option should list

• The asbestos survey result, and who took the samples.
• The structural engineer’s name, and the written assessment of purlins, trusses and fixings.
• For overcladding: the fixing method through the sheets, the dust controls from the list above, and what happens inside the building while the work goes on.
• For stripping: the method statement, the Category B training evidence, the netting and access arrangements, the waste carrier and the consignment paperwork.
• How roof lights and any twin-skin or liner build-up are dealt with.
• Who has responsibility for the asbestos register once the work is done.
• What the array installer needs from the roofing contractor, and how the two programmes meet.

On price

This guide gives no price per square metre, because none of the guidance above publishes one and a figure without a source is not worth printing. Many of the pages that answer “asbestos roof removal cost” in the UK search results (checked 20 October 2026) are written for domestic garages and small sheds, and their prices do not transfer to a farm building with height, access, roof lights and a skip. What changes the price on a farm roof is the area, the access and height, the netting, the number of roof lights, the condition of the purlins, whether the building stays in use, and the waste. Ask for the quote to price each of those separately so two quotes can be compared.

For the wider picture of solar on sheds, stores and workshops, see solar panels for agricultural buildings, and for the material itself the posts on asbestos cement and fibre cement roofs and asbestos cement barn roofs and solar.