When the re-roof and the array belong in one project
On a pre-2000 farm building the roof is often asbestos cement, and installers will not normally fix through it. If the roof is near the end of its life anyway, doing the re-roof and the array as one project means one set of access arrangements and one scaffold or platform, and it lets the new roof be designed with the array in mind: fixing positions on the purlins, the rooflights, the walkways. If the roof is sound and the sheets are intact, the alternatives are to leave it and put the array on another roof or on the ground, or to overclad it. The legal position, which does not oblige anyone to remove sound asbestos cement, is on solar panels on asbestos cement farm roofs; the timing question is in farm solar and roof replacement timing.
The order of work
- Survey first: asbestos testing and the condition of the sheets, rooflights and structure (the full list is in the farm roof survey for solar PV guide).
- Decide the route for the old roof: strip it, overclad it or leave it. HSE’s task sheet A14 asks whether the sheets can be overlaid instead of removed, and NFRC’s guidance sheet HSGS44 says that if the purlins are degraded or overstressed, removal may be the only viable option. The comparison is in overclad or strip an asbestos cement farm roof.
- Have a qualified structural engineer assess the frame for the added dead and live load. NFRC names solar panels among the loads the original structure may not have been designed for.
- Appoint operatives trained for non-licensed asbestos work (Category B in the NFRC guidance), with netting, waste consignment and a method statement agreed before the first sheet comes off.
- Build the new roof with the PV support positions fixed in the design, then fix the array to the new roof, not to old sheets.
- Apply to the DNO for the G99 connection early: it sets its own study timescales, and they run alongside the roof work (DNO grid connection for rural farm solar).
The loading check on a re-roof
Approved Document A (England) treats re-covering of roofs as the point at which the roof structure is checked: where the loading is increased by more than 15% the structure and its supporting structure should be checked, and if it cannot sustain the increase, strengthening is a material alteration. Many agricultural buildings are exempt from the Building Regulations under Schedule 2 Class 3, in which case no building control body makes the check and the owner and installer must. The module weights and the questions to ask are in solar panel weight and roof loading on farm buildings.
Fire classification of the new roof
RC62, the insurers’ code of practice for rooftop PV, asks for PV on non-combustible roofs meeting Class A1 or A2-s1,d0 to BS EN 13501-1, says a new installation shall not lower the roof’s fire classification, and singles out composite sandwich panels with a combustible core. A re-roof is the moment to choose the build-up; the clauses are set out in solar panel fire risk on farm buildings, and what the insurer will ask is in solar panel insurance for farm buildings.
What qualifies for tax relief
Plant and machinery, which includes the PV system, can be written off in the year of purchase under the Annual Investment Allowance. Building fabric such as the re-roof is generally treated differently, so ask the accountant how the invoice should be itemised before the contract is signed. The reliefs and open schemes are on grants and funding.
What to ask for
- The asbestos survey result and who took the samples.
- The structural engineer’s name and the written assessment.
- The route chosen for the old roof and the method statement for it.
- The roof build-up and its fire classification.
- An itemised price that separates the re-roof from the array.
- A programme that names its dependencies: survey, DNO study, weather and the farm’s own calendar.
If the old sheets are asbestos cement and come off, the packing, carrier and consignment-note rules are in disposal of asbestos roof sheets from a farm building.
The older barn-roof guide, asbestos cement barn roofs and solar, covers how pre-2000 farm buildings are usually handled.
Common questions
What does a combined re-roof and solar project include?
An asbestos survey, a decision on the old roof (strip, overclad or leave), a structural assessment, the new roof built with the array’s fixing positions in the design, the array itself and the grid connection application. The order of work is set out above.
Is the re-roof eligible for the Annual Investment Allowance?
The PV system is plant and machinery and can qualify. Building fabric such as the re-roof is generally treated differently, so ask the accountant how the invoice should be itemised before signing.
Does the roof need a structural check?
Yes. In England, Approved Document A treats a loading increase of more than 15% on a re-covered roof as significant, and many agricultural buildings are exempt from the Building Regulations altogether, so the check has to be asked for. See the guide to solar panel weight and roof loading on farm buildings.
How long does it take?
The programme depends on the asbestos survey, the DNO’s G99 study, the roofing work and the weather, so ask for a written programme that names those dependencies. No fixed timescale is published for this page.