Why the roof is surveyed before anything else is priced
A price for farm solar that has not seen the roof is an estimate of the array, not of the project. The roof decides whether panels can go on at all, what has to be done first, and what the structure has to carry. NFRC’s guidance sheet HSGS44, written for contractors, designers and clients working on cement-sheet roofs, starts from a comprehensive survey, and the list below follows it, with the electrical and access items a solar project adds.
What the survey should find
- Asbestos. Testing to establish whether asbestos is present, its type and its quantity. On a pre-2000 roof treat the sheets as asbestos cement until a test says otherwise. The legal position and the options are on solar panels on asbestos cement farm roofs and overclad or strip an asbestos cement farm roof.
- Condition of the roof. The sheets, rooflights and glazing, gutters and fixings. HSE’s asbestos task sheet states that asbestos cement roofs are always fragile and cannot bear weight, so access is part of the survey, not an afterthought.
- The structure. Frame, purlins and supports, including corrosion and any sign of overstress. A qualified structural engineer assesses whether the structure can accept the added dead and live load, as NFRC advises; see solar panel weight and roof loading on farm buildings.
- The construction build-up. Historic roofs may be twin-skin insulated systems, liner systems or spacer arrangements rather than single-skin sheets, and the build-up should be understood before a strategy is chosen.
- The electrical supply. Single or three-phase supply, the main switchgear and where an inverter and isolators could sit, and what the DNO will need for the G99 application (DNO grid connection for rural farm solar).
- Access and surroundings. Internal and external access, overhead power lines and ground conditions for cranes or hoists, all of which NFRC lists.
- Fire and insurance points. Roof classification, cable routes, rodent and bird access, and anything the insurer will ask about (solar panel fire risk on farm buildings, solar panel insurance for farm buildings).
The report to ask for
A written report that names who carried out each part, shows the test results and photographs, states the condition of each building’s roof and structure, and says what has to be done before panels can go on. Ask whether the survey and the structural assessment are separate documents and who is accountable for each; where a building is exempt from the Building Regulations, no building control body will make the structural check for you.
Where the survey fits
The survey is the step after a desk-based farm solar feasibility study and before a priced proposal. Planning questions are in planning permission for solar on farm buildings, and the cost baseline is in the farm solar cost guide.
Ask for the roof-access method before survey day; fragile roofs and solar installation on farm buildings lists the HSE rules that method has to meet.
Common questions
What does a farm solar roof survey cover?
Asbestos testing, the condition of the sheets, rooflights and gutters, the structure and its capacity for the added load, the construction build-up, the electrical supply and the access arrangements. The full list is above.
Who should do the structural assessment?
A qualified structural engineer. NFRC’s guidance says to engage one to assess the structure’s capability to support additional dead and live loads, whether the old roof is stripped or overclad.
Does the survey need to test for asbestos?
On a pre-2000 roof the sheets should be treated as asbestos cement until a test says otherwise. NFRC’s guidance lists testing for the presence, type and quantity of fibres as part of the survey.