MCS published an update to The Solar Mounting (Product) Standard, MCS 012 v3.0, on 10 May 20231. One change was the expansion of scope to include mechanically attached and non-mechanically attached mounting systems designed for installation on flat roofs of 10 degrees or less1.
Before that expansion, installers relied on clause 5.5.5 of The Solar PV Installation Standard (MIS 3002) where no certified flat roof mounting system existed1. The clause states:
"Where there are no MCS 012 certified mounting systems suitable for a given installation, a custom designed mounting system may be used subject to the following being met: a) The system is compliant with current Building Regulations for weather-tightness, fire and wind resistance. b) The system designer and/or fixing supplier must confirm in writing that the final installation is in accordance with a) above and its instructions."
Once the standard allowed flat roof mounting systems to be certified, clause 5.5.5 was no longer to be acceptable as a means of compliance for flat roof installations1. MCS then granted an extension of its use, because manufacturers were still working through certification1. The dates have moved more than once:
| Date | Position on clause 5.5.5 for flat roofs |
|---|---|
| 1 May 2025 | Permitted until 10 August 20252 |
| 23 June 2025 | Extended to 10 November 20251 |
| 23 October 2025 | Extended until further notice3 |
The 1 May 2025 notice said MCS was hosting its next Solar PV technical working group meeting on 12 May 2025, where clause 5.5.5 would be reviewed2. The 23 October 2025 notice said MCS would immediately support the Technical Working Group to review clause 5.5.5, with the outcome implemented and communicated in the coming weeks, and would also review MCS 012 itself to address challenges manufacturers face and to enable certification of non-mechanically attached products3. That extension continues until MCS has reviewed MCS 012 and there are enough certified flat roof mounting kits for installers to choose from3. MCS said certified installers should continue to refer to the current version of clause 5.5.53.
Why it matters for households
The mounting system is what holds a solar panel array to a roof, and on a flat roof it carries wind uplift and weather-tightness risk that a pitched roof handles differently. The route by which a flat roof installation is judged compliant affects whether an MCS certificate can be registered for the work, and that certificate is the document behind most grid and payment schemes. Under the extension, an uncertificated mounting system on the flat roof of a permanent building can still be registered, provided the clause 5.5.5 conditions are met1. Those conditions place written confirmation on the system designer or fixing supplier that the installation complies with Building Regulations for weather-tightness, fire and wind resistance1. Households with a flat roof, or a roof at a shallow pitch, are therefore in a period where the paperwork trail behind the mounting system matters as much as the panels. The mounting systems used on such roofs are made by a small number of manufacturers, and certification status sits with the product rather than the installer.
What happens next
MCS has said the clause 5.5.5 review outcome will be implemented and communicated in the coming weeks, and that MCS 012 will be reviewed to address manufacturer challenges and to enable certification of non-mechanically attached products3. No date has been given for either. The extension of clause 5.5.5 runs until further notice, ending when MCS has completed the MCS 012 review and enough flat roof mounting kits hold certification3. No further dates have been reported.
Sources3 cited
- Extension for the use of flat roof solar mounting products - MCS, mcscertified.com
- An update for Solar PV flat roof mounting systems - MCS, mcscertified.com
- MCS provides an update for Solar PV flat roof mounting systems - MCS, mcscertified.com