MCS 012 In-Roof Solar Fire Classification Guide: What MGD 008 Means

What Happened

In late 2023, MCS's Solar Mounting Working Group found that a change to a European standard, in effect since September 2023, had left it unclear how roof-integrated solar PV mounting systems could get a fire classification. Where solar modules form the roof covering, a fire classification is the main way to show that the roof meets the external fire requirements in building regulations, and it is needed for certification under MCS 012, MCS's solar mounting product standard.

MCS says it convened government, the Health and Safety Executive, the Building Safety Regulator and the British Standards Institution to look for a way to keep certification possible. On November 2, 2026 it published the testing guidance, MGD 008. It also said it will release a supplementary interpretation note in the coming weeks, which explains how the changes to BS EN 15725:2023 can be read for MCS certification and gives certification bodies a route to certify products under MCS 012 while a suitable BSI standard is missing.

MCS also pointed to the scale of what is at stake: solar is its most popular technology, with more than 2.1 million certified installations, and the Future Homes Standard is set to make solar the default on new builds from next year.

Why It Matters for In-Roof Systems

MCS's installation standard for solar, MIS 3002, says systems mounted above or integrated into pitched roofs must use products tested and certified to MCS 012. For a roof-integrated system, MCS 012 requires fire testing. Without a fire classification, a new in-roof product cannot get an MCS 012 certificate.

A 2025 trade report said exactly that: new products could not obtain a fire classification, so they could not be built into roofs in line with the Building Regulations or gain MCS certification. MGD 008 is MCS's response for the testing side.

What MGD 008 Covers

The guidance explains why extension by judgement is excluded. BS EN 15725:2023 clarifies that extended application must come only from codified rules and established principles in the applicable standards, so expert judgement is no longer part of the method. Writing those rules is outside the scope of MGD 008.

How the Testing Works

The guidance asks the test sponsor, usually the manufacturer, to build a test plan that picks out every place on the array where fire could get in or spread. The example in the document lists twelve reference locations, among them:

• fixing points at the upper, lower and side edges;
• junctions between panels, including multi-way junctions;
• the junction between the array and the surrounding roof covering;
• the centre of a module; and
• any cables or conduits between panels and the roofing, which must be included so that every fire route is checked.

Roof geometry matters too. Hips, valleys and stepped layouts create different junctions, and the guidance says complex geometries that cannot be represented in the test rig may fall outside it.

Each location in the plan is treated as a separate exposure location. The radiant heat footprint of the test apparatus is limited to about 840 mm by 840 mm, so each location must be built to fit it, and oversized specimens cannot be reused for several locations because earlier heat can affect later results.

MCS's worked example makes the scale clear. A plan with four test areas needs three Stage 2 specimens for each, which comes to 12 penetration tests.

The guidance also asks laboratories to record more than the standard requires: delamination of system components, the last damaged layer, the behaviour of cable routing and electrical components, how far fire spreads through cavities or interfaces, and how flashings and edge details perform. Test reports must include the test plan, drawings, photographs, the bill of materials and the version-controlled installation instructions.

What Is Still Open

• The interpretation note. MCS has not published it yet, so the route to certification under MCS 012 for products without a suitable BSI standard is not final.
• Extended application. Rules for extending test results to product variations are not covered.
• Complex roofs. Systems whose layout cannot be reproduced in the rig may fall outside the guidance.
• Other product safety rules. BIPV products may also need to meet fire-related requirements in BS EN IEC 61730-2 and the BIPV standards EN 50583-1 and EN 50583-2, which are outside MGD 008.
• Building regulations. The guidance points to the current edition of Approved Document B and its forthcoming 2026 and 2029 changes, so the assessment basis may move.

What This Means for Installers and EPCs

• The testing burden sits with manufacturers, not installers. MGD 008 is aimed at test laboratories, sponsors and certification bodies.
• Check the certificate for any in-roof job. Ask for the product's MCS 012 certificate and its fire classification, and confirm it applies to the exact system you are installing, including the module.
• Plan new-build in-roof work with care. With solar becoming the default on new homes under the Future Homes Standard, in-roof products are likely to see more demand, but new products still need classification. Keep an above-roof option in the specification until a product's certificate is confirmed. Our Future Homes Standard guide covers the new-build requirement.
• Watch for the interpretation note. It will show how certification bodies can proceed, and whether more products can be certified soon.

Where Design Software Fits

Whether a roof suits in-roof or above-roof panels starts with the roof layout. Design software like Reslink produces the layout, bill of materials and single line diagram for a project, so options can be compared on one roof model. It does not test or classify products for fire performance.

See the full workflow → Book a demo

Frequently Asked Questions

Q1. What is MGD 008?

An MCS guidance document for test laboratories on identifying and fire testing roof-integrated solar PV mounting systems to DD CEN/TS 1187:2012 Test 4, published on November 2, 2026.

Q2. Why does an in-roof system need a fire classification?

Where the modules form the roof covering, a fire classification is the main way to show compliance with external fire requirements in building regulations, and it is required for MCS 012 certification.

Q3. What changed in 2023?

A change to a European standard that took effect in September 2023, BS EN 15725:2023, left it unclear how roof-integrated systems could get a classification.

Q4. Does MGD 008 cover on-roof systems?

No. It excludes above-roof systems, façade-integrated systems and systems assessed by extended application.

Q5. How many tests does a system need?

Each test location needs a preliminary test on one specimen and a penetration test on three specimens. MCS's example with four locations needs 12 penetration tests.

Q6. Is the route to certification settled?

Not yet. MCS says an interpretation note for certification bodies will follow in the coming weeks.

Q7. What should an installer ask a supplier?

For the MCS 012 certificate, the fire classification, and confirmation that it covers the exact module and mounting combination being installed.

Final takeaway

MGD 008 gives manufacturers and test laboratories a consistent method for classifying in-roof solar systems, and MCS 012 certification depends on that classification. For installers the practical step is to ask for the certificate and classification before specifying an in-roof product, and to watch for MCS's interpretation note.

You May Also Like

• Future Homes Standard 2027: Solar Requirement L3 for UK Installers
• MCS 2027 Deadline: What's Actually Changing for Solar and Battery EPCs
• MCS 042: UK Battery Product Standard Proposals and Nov 10 Deadline

Sources

• MCS, MCS publishes guidance to address solar PV module fire classification challenges (November 2, 2026)
• MCS, MGD 008 Issue 1.0: Guidance Document for Test Laboratories, Identification and Testing of Roof Integrated Solar PV Mounting Systems (November 2, 2026)
• MCS, MCS 012 Issue 3.0: The Solar Mounting Standard
• MCS, MIS 3002: Solar PV Installation Standard
• Roofing Today, MCS Leads on Solar PV Fire Testing Classifications (2025), for the earlier certification gap

This guide reflects MCS's announcement and MGD 008 Issue 1.0 as of November 4, 2026. MCS has said more guidance will follow, so check MCS's website for the interpretation note and for any change to MCS 012.