CROSS Safety Report
Loading from solar panels
This report is over 2 years old
A reporter inspected a roof to discover that the structure was already overloaded with the self weight of the roof covering without the addition of solar panels.
Key Learning Outcomes
For solar panel suppliers, installers, and homeowners:
All roofs should be appraised by a competent and suitably qualified engineer for the suitability of accommodating solar panels
Inspection by a competent person should be carried out to ensure the works are installed in accordance with the design intent
For civil and structural design engineers:
Load effects of snow and wind uplift acting on the roof structure due to solar panels should be carefully considered, particularly for sliding snow
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Another reporter visited a dwelling which already had a two solar panels installed on the roof and where the owner then wished to have more. The reporter inspected the roof framework and advised the panel supplier that the structure was already overloaded with the self weight of the roof covering without the addition of solar panels.
The property was built in 1971 and has a very slim roof structure which, in the opinion of the reporter, would be in danger of collapse if a snow load of any significance were to be added to the loading of the weight of any solar panels on an already overstressed structure.
Expert Panel Comments
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The installation of solar PV panels is a material alteration under the building regulations and needs assessment. In England this is to be done either under a competent persons scheme (such as the MCS scheme) or the local authority requires notification. Some competent person’s schemes only operate for electrical requirements of the regulations and then need the local authority to check other relevant aspects such as Parts A and C of the building regulations.
Issues of loading on existing roofs whether wind or snow or dead therefore come under control. Clearly there is a need to assess whether an existing roof structure can carry the extra load and that applies globally and locally (at fixing points). But there are additional concerns.
In the past CROSS has reported on many cases of danger following parts becoming detached from roofs. It is essential that panels are properly fixed down against the very high suction loads that might occur. In areas of higher snow load sudden thaws can cause snow slides with significant impact and danger if the slides fall on people or adjacent lower lying roofs.
It is essential that panels are properly fixed down against the very high suction loads that might occur
Are concerns likely to increase?
The potential for large slides might exist given the nature of panel surface material. The concerns are likely to increase as pressure to reduce energy consumption grows. Insufficient attention being paid to structural integrity is not new on small works. The examples quoted above all relate to competence and so far, the solar panel industry is unregulated.
Notwithstanding this the installation of solar panels is covered by the CDM Regulations and hence all those involved have statutory duties to safeguard others. It may be that a code of practice could be a good starting point. The Scottish Government has published a report: Risk assessment of structural impacts on buildings of solar hot water collectors and photovoltaic tiles and panel – final report.
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