Standards Library · 04
MIS 3002 V6.0
MCS structural requirements
The Microgeneration Certification Scheme technical standard for solar PV. Issued 18 March 2026, mandatory from 18 June 2026, applying to installations up to 50 kWp DC. It requires a qualified structural engineer in named cases, and every ballasted system is one of them.
What it is
On pitched roofs, which the standard defines as steeper than 10 degrees and shallower than 70, clause 5.9.4 requires the MCS Contractor to ensure the roof structure is checked by a suitably competent person to confirm it can withstand the loads imposed by the system. That person need not be an engineer. Flat roofs, under 10 degrees, are dealt with separately at 5.9.11 to 5.9.13.
A qualified structural engineer is required in two places. Clause 5.9.6: where the roof structure is in any way unusual, or there is any doubt whatsoever, an engineer shall be consulted. Clause 5.9.13(h): on ballasted systems an engineer shall be consulted to confirm the roof can withstand the load from both the array and the proposed ballast. Table 1 adds a third route, sending traditional cut timber roofs with hips or valleys, and asymmetric duo-pitched roofs, straight to consult a structural engineer.
The 5.9.6 Note defines an unusual roof as any that is not shown in Table 1, shows signs of structural distress, shows signs of post-construction modification such as removal of timbers, notching or a change of covering to a heavier material, has a particularly shallow pitch under 30 degrees, or has increased potential for snow build-up, for example dormers, valleys and parapets.
It governs installations within the scope of the Microgeneration Certification Scheme. Work above the scheme's 50 kWp DC threshold is not covered by it at all, which is a common source of confusion on larger commercial schemes.
Why it matters for rooftop solar
The standard is misstated in both directions, and both are costly. Told it never requires an engineer, an installer walks into a ballasted flat roof job that always does. Told it always requires one, a client pays for engineering on a simple pitched roof where 5.9.4 would have been satisfied.
One clause is routinely misread as an engineer requirement and is not one. Clause 5.5.5 covers mounting systems outside the scope of MCS 012. Its item (b) requires evidence that a structural assessment and a wind loading calculation have been completed for the specific mounting system. The Note permits that evidence to come from the system manufacturer, from a third-party structural engineer, or from an appropriate software platform. An engineer is one of three routes, not a requirement. The standard adds that these calculations do not constitute compliance alone and must be directly linked to the design and installation of the system.
Clause 5.5.5 is also the headline change in V6.0. The standard's own amendment record gives the reason for the 18 March 2026 issue as "Extension to clause 5.5.5 and other small corrective amendments". The version everyone is asking about was issued principally to extend the non-MCS 012 mounting route.
If the array is ballasted on a flat roof, a qualified structural engineer is mandatory. 5.9.13(h) admits no exception, and flat roofs are exactly where ballast becomes the governing load. This is the single most commonly missed requirement in the standard.
Beyond the named cases, applying the engineer standard to all commercial work is our own position, not the regulation's. We separate the two deliberately, because a supplier who blurs them is selling on a compliance claim that will not survive being checked.
Because the standard does not specify the deliverable, two assessments can both be compliant and share almost nothing. That gap is what the Assessment Specification was written to close.