BMG Surveys warns solar industry not to confuse structural screening with structural assessment.
Managing Director Bryan McGrory calls for a clearer line between screening tools and genuine engineering judgement as LABC and MCS review their structural guidance.
Bryan McGrory, Managing Director of BMG Surveys Ltd, has called on the UK solar industry to draw a much clearer distinction between structural screening and structural assessment, warning that structural suitability for a permanent PV installation should not be determined by a simplified screening methodology or software-generated 'green tick', but through an appropriate structural assessment undertaken by a suitably competent person.
The comments come as both LABC and MCS review the structural guidance underpinning rooftop solar installations. LABC has confirmed to BMG that it intends to review and remove parts of its Guide to Retrofitting Solar Panels, following concerns raised over the structural guidance it contained, and has said this is an area where the industry sector and relevant specialists should take the lead in providing appropriate guidance while the subject remains under review. The structural methodologies historically used within the MCS framework are also currently under review.
McGrory argues that the UK solar industry has become highly sophisticated at the electrical and commercial side of PV design, modelling generation, optimising panel layouts and forecasting performance over decades, but that structural suitability has too often been reduced to a tick-box exercise, with a few measurements entered, assumptions made, and a green tick appearing on screen.
Bryan McGrory said: "Software can support the process. A structural calculation should calculate. An engineering judgement should be made by someone competent to make it. A green tick on a screen should never replace either."
A solar installation, McGrory says, is a structural alteration. Once panels and mounting systems are installed, they become a permanent addition to a building and change its structural loading condition. A proper assessment needs to consider the existing roof construction, permanent actions, appropriate roof-imposed loading, snow, wind and the proposed PV system together, combined through the relevant load combinations, rather than in isolation. Generic assumptions can fail in both directions: an assessment that stacks every conceivable load onto a roof may unnecessarily condemn a perfectly adequate structure, while treating an existing design allowance as spare capacity for PV can also be wrong.
McGrory is clear that digital tools and software have an important role in the solar industry. They can improve data collection, standardise workflows, assist design coordination and ensure the right information reaches the right professional. What they should not do is determine whether an existing structure is suitable to support a permanent PV installation.
That conclusion, he says, should come from an appropriate structural assessment undertaken by a suitably competent person, with a clear and auditable chain of responsibility covering who carried out the survey, who undertook the assessment, what training and experience they hold, and whether professional indemnity insurance actually covers the work undertaken. McGrory concluded: "The question is not whether a piece of software can produce a green tick. The question is whether, five, ten or twenty years from now, when a homeowner, landlord, insurer, purchaser, lender or another engineer asks, 'How do we know this roof was suitable for the solar installation?', there is a credible answer."
