What building regulations apply to commercial solar installations?

Commercial solar installations in the UK must comply with several Building Regulations and electrical/safety standards. The most relevant are: Part A (Structure), Part B (Fire Safety), Part L (Energy Efficiency), and Part P (Electrical Safety) of the Building Regulations 2010. Electrical work follows BS 7671 (the IET Wiring Regulations, currently 18th Edition with Amendment 2). Construction (Design and Management) Regulations 2015 (CDM 2015) apply where the project exceeds 30 person-days. MCS (Microgeneration Certification Scheme) commercial certification or equivalent NICEIC accreditation is required to commission the install legally, sign it off via building control, and unlock the Smart Export Guarantee. Asbestos surveys are required for any pre-2000 building roof.

Part A — Structural

Solar PV adds weight to a roof: typically 12-20 kg/m² depending on panel and mounting type. The structural engineer confirms the roof can take this load alongside snow, wind, and live loads. Methodology:

• Drawings review (or measured survey if drawings unavailable)
• Calculation per Eurocode 1 (BS EN 1991) for loadings
• Calculation per Eurocode 3 (steel) or Eurocode 5 (timber)
• Wind uplift assessment to BS EN 1991-1-4
• Sign-off by chartered structural engineer (CEng MIStructE or MICE)

Most modern (post-1990) commercial buildings pass structural assessment without modification. Older steel-portal frames sometimes need additional bracing or load redistribution. Pre-1980 buildings, especially with timber decks, often require strengthening.

Part B — Fire safety

Solar PV interacts with fire strategy in several ways:

1. DC isolation: in a fire, firefighters need to know how to isolate DC. Most commercial systems use rapid shutdown devices (panel-level optimisers force DC voltage to safe levels at module level when AC is removed).
2. Cable routing: DC cabling must avoid escape routes, fire compartments, and high-risk areas. BS 7671 Section 712 governs.
3. Fire alarm integration: insurer often requires PV system to be integrated with the fire alarm so it shuts down on activation. Cost £500-£2,500.
4. Roof construction: panels alter roof fire spread classification. Class A or B roof coverings are required (most commercial roofs already comply).

Part L — Energy efficiency

Part L covers the building’s overall energy performance. Commercial solar contributes to:

• EPC rating uplift (typically 1-2 bands)
• MEES compliance (currently band E minimum, band C by 2027, band B by 2030 for non-domestic let)
• Net Zero Carbon Building Standard (where pursued)

A new EPC must be issued post-install showing the improved rating. Cost £180-£500 per EPC for commercial.

Part P — Electrical safety

Commercial PV installs are exempt from Part P (which targets domestic). Instead they must comply with BS 7671 Part 7 Section 712 (Solar PV power supply systems). All work by qualified electricians, certified by MCS/NICEIC commercial accreditation.

CDM 2015

The Construction (Design and Management) Regulations 2015 govern construction project safety. They apply to all commercial solar installs but with different requirements based on scale:

Project size	CDM duties
Under 30 person-days, single contractor	CDM applies — duty holders defined, F10 may not be required
Over 30 person-days OR multiple contractors	F10 notification to HSE required, Principal Designer + Principal Contractor required, Construction Phase Plan mandatory
Over 500 person-days	Additional notification thresholds

A 100 kW SME install typically lands at 35-50 person-days — F10 notification required.

Other regulatory checks

Asbestos survey

Pre-2000 buildings need a Refurbishment & Demolition asbestos survey before roof penetrations or fixings can be installed. Cost £400-£1,200. If asbestos is present, encapsulation or removal required before install.

EPC update

Required post-install. £180-£500.

Insurance notification

Most commercial property insurers require notification of solar PV. Some require type-test certification, MCS sign-off, and integrated fire alarm shutdown. Confirm with broker before commissioning.

DNO grid connection

G98 (sub-50 kW per phase, total sub-100 kW typically) or G99 (above) — see our separate FAQ on this.

Worked compliance flow for a 100 kW install

1. Structural survey (Part A) — week 1
2. Asbestos survey (pre-2000 building) — week 1
3. Detailed design and BS 7671 cabling design — weeks 2-3
4. CDM Construction Phase Plan, F10 notification — week 3
5. DNO G99 application — week 3 (long lead)
6. Building control plans submitted — week 4
7. Install — weeks 12-16 (after DNO approval)
8. MCS commissioning — week 16
9. Building control sign-off — week 17
10. EPC update — week 17
11. Insurer notification + fire alarm test — week 17
12. SEG application + smart meter installation — week 18

Common misconceptions about solar building regs

“Building regs don’t apply to PV” — wrong. They apply to all parts of the install touching structure, fire, and electrical.

“Building control sign-off is automatic” — wrong. The local authority building control (or approved inspector) reviews drawings and inspects the install.

“You don’t need an asbestos survey” — wrong for any pre-2000 building. Penalty for breaching CAR 2012 is significant.

“MCS isn’t required for commercial” — incorrect. MCS commercial or equivalent (NICEIC, RECC) is required to: legally commission, sign off via building control, qualify for SEG.

Next steps

For a fully compliant feasibility study, contact us. See planning rules, G98 vs G99, grants page, and cost guide.