Search for the flat-roof mounting deadline and you will be told 10 August 2025. Third-party blogs, reposted LinkedIn summaries, the odd supplier newsletter. The date is wrong.
MCS extended it to 10 November 2025. The extension took effect on 20 June 2025 and was published on 23 June 2025. Almost everything written before that date carries the August cut-off, and a fair amount written afterwards copied it across without checking.
That is the whole answer, if it is all you came for. The rest of this page is the chronology, why the superseded date has proved so durable, and what is actually left to check on a flat-roof quote now the route is closed.
What MCS changed
On 1 May 2025 MCS published a notice on solar PV flat-roof mounting systems. Its terms were plain:
"clause 5.5.5 in The Solar PV Installation Standard will no longer be acceptable as a means of compliance for flat roof installations."
The Solar PV Installation Standard is MIS 3002. That notice set the cut-off at 10 August 2025.
What clause 5.5.5 says, and how the trade had been reading it, is beside the point for our purposes. MCS's position is what matters: the current interpretation of that clause, in relation to flat roofs, is no longer an acceptable route to compliance. If you want the clause text, take it from MIS 3002 itself rather than from anyone's summary of it, this one included.
Then, on 23 June 2025, MCS published a second notice:
"The current interpretation of clause 5.5.5 in relation to flat roofs was permitted until 10 August 2025, as of 20 June 2025 this has now been extended to 10 November 2025."
Read that sentence slowly, because it carries three dates and people routinely pick the wrong one. 10 August 2025 is the date that was superseded. 20 June 2025 is when the extension took effect. 10 November 2025 is the operative deadline.
The chronology
| Date | What happened |
|---|---|
| 1 May 2025 | MCS publishes its notice on flat-roof mounting systems, setting the cut-off at 10 August 2025 |
| 20 June 2025 | The extension takes effect |
| 23 June 2025 | MCS publishes the extension notice |
| 10 August 2025 | The original cut-off. Superseded, and still widely quoted |
| 10 November 2025 | The operative deadline |
Why the August date will not die
Because it was correct for seven weeks. Any post written between the two notices, quoting 10 August 2025, was accurate on the day it went up. Nobody returns to edit a compliance explainer once the traffic has tailed off, and a page that has sat there for a year tends to outrank the correction.
So the wrong date propagates. It gets summarised into a newsletter, screenshotted into a WhatsApp group, and read aloud at a toolbox talk by someone who has no particular reason to doubt it.
A rule that costs you nothing: if a page gives you an MCS date, look at when the page was published. Anything dated before 23 June 2025 is describing a world that no longer exists. Anything dated after it should say 10 November 2025, and if it does not, that tells you something about how carefully the rest of it was written.
This post exists because the internet is full of the superseded date. Correcting a search result is not a service anyone should have to provide. Here we are.
What is left to check on a flat-roof quote
With the clause 5.5.5 route closed, the practical residue is short. Flat-roof mounting products need to be certified to MCS 012, the mounting-system product standard. Two things follow, and both belong at quote stage rather than on site:
The mounting system you specify is certified to MCS 012. That is a question for your mounting supplier and, if you want it in writing from someone who will be auditing you, your certification body. It is not a question for a blog, and this page is not going to hand you a list of certified products.
You can evidence it. This is where firms come unstuck. Certification that exists somewhere, in a supplier email from eighteen months ago, in a PDF on a laptop that has since been replaced, is for audit purposes certification you do not have. Attach the documentation to the job. Keep it retrievable by whoever picks up the file when you are on a roof.
Neither of these is difficult. Both are the kind of thing that gets skipped in the fortnight when you are quoting three commercial flat roofs and someone is off sick.
Jobs completed before the deadline
The obvious question, and one this page will not answer: what becomes of flat-roof installations completed and registered under the old interpretation, before 10 November 2025.
That is a matter for your certification body. Ask them directly, ask in writing, and keep the reply with the job file. Anybody answering that question confidently in a blog post is guessing, and a guess about retrospective compliance is worth precisely what you paid for it.
Where this sits in the wider redevelopment
The MCS redeveloped Installer Scheme is rolling out throughout 2026 and into 2027, and it reaches every certified installer. MCS's own framing is that the technical requirements have been restructured rather than changed.
Hold that framing alongside the flat-roof change, because the two are different in kind. Restructuring how a requirement is presented is not the same as withdrawing a means of compliance. Clause 5.5.5, for flat roofs, was the second. It is worth being able to tell the difference when the next notice lands, because the notices that restructure can be read at your leisure and the notices that withdraw a route cannot.
Before your next flat-roof quote
- Use 10 November 2025. If a source says 10 August 2025, check its publication date, then stop using that source.
- Confirm the mounting system on the quote is certified to MCS 012, and confirm it before the price goes out, not after the customer has signed.
- File the certification evidence against the job, somewhere a colleague could find it without ringing you.
- Put the pre-deadline question to your certification body in writing, and keep the answer.
- Read MIS 3002 from MCS. Not from a summary of it.
The last point generalises. Every fact on this page comes from an MCS notice, linked below, and you should click them rather than take our word for it. The mounting system is a specification decision, made when the quote is written rather than settled later on the van, and that is the view Solar Engine is built on. It is also the reason the date matters: by the time anyone is on the roof, the decision that had to be compliant was made weeks ago.