Working on Commercial Properties: Different Standards, CDM Principal Contractor Role and Contractor Assessments

Quick Answer: Commercial properties have different regulatory standards from domestic — commercial electrical work follows BS 7671 but with specific commercial circuit requirements; gas work follows IGEM commercial standards (not just domestic); building work follows different occupancy class requirements under Part B (fire) and Part M (access). On projects worth more than £500,000 or with more than 500 person-days of construction, CDM 2015 requires a Principal Designer and Principal Contractor. Commercial clients also expect documented contractor assessments (typically via Constructionline, CHAS, or SafeContractor).

Summary

Many tradespeople who primarily work on domestic properties occasionally take on commercial work: a small office refit, a restaurant kitchen installation, a church hall repair. The transition from domestic to commercial involves more than just a larger invoice — there are different technical standards, different regulatory triggers, and different procurement and compliance expectations.

The most common mistake is assuming that domestic competence translates directly to commercial environments. A plumber confident in domestic gas work who installs a commercial catering appliance without understanding IGEM commercial standards is exposed to regulatory risk. An electrician who installs a new consumer unit in an office using domestic-style practices may fail a commercial EICR.

The Construction (Design and Management) Regulations 2015 (CDM 2015) add a layer of formal project management obligations that rarely arise in domestic work. For any project meeting the CDM thresholds, specific duty holders — Principal Designer, Principal Contractor — must be appointed. Tradespeople working on larger commercial projects are likely to encounter CDM requirements and should understand their obligations as contractors.

Key Facts

• CDM 2015 — Construction (Design and Management) Regulations 2015; applies to all construction work; more formal requirements for notifiable projects
• Notifiable project (CDM) — Construction work lasting more than 30 working days with more than 20 simultaneous workers, OR more than 500 person-days total
• Principal Designer — Appointed by the client; coordinates health and safety during design phase; must be appointed for projects with more than one contractor
• Principal Contractor — Appointed by the client; manages health and safety on site during construction phase; must be appointed for projects with more than one contractor
• Contractor role (CDM) — Any tradesperson engaged on a CDM project must: plan their work, cooperate with PC, not create unsafe conditions
• Health and Safety File — Created by Principal Designer; updated by Principal Contractor; handed to client on completion; required for all multi-contractor projects
• F10 notification — Required for notifiable projects: notify HSE before construction starts; done by Principal Contractor
• Commercial electrical standards — BS 7671 applies universally; but commercial SWA cables, containment, distribution boards, and circuits differ from domestic
• SWA cable — Steel wire armoured; standard for commercial power distribution; mechanical protection; armour is the earth
• IPAF/PASMA — For working at height commercially: IPAF (powered access) or PASMA (mobile tower) certification increasingly required
• Contractor vetting — Commercial clients expect documented competency assessment; common schemes: Constructionline, CHAS, SafeContractor, Achilles, ISO 9001
• RAMS — Risk Assessments and Method Statements; required by commercial clients before work begins on site
• Commercial gas — IGEM UP/1A (tightness testing); IGEM UP/2 (commercial installation); Gas Safe registration still required but additional IGEM standards apply

Quick Reference Table

Detailed Guidance

CDM 2015: Understanding Your Role

CDM 2015 categorises everyone involved in construction into duty holders with specific legal obligations.

The five duty holders:

1. Client: The person or organisation commissioning the construction work. All clients must: ensure competent designers and contractors are appointed; ensure sufficient time and resources for the project; ensure a Construction Phase Plan is prepared; ensure a Health and Safety File is created.

2. Principal Designer (PD): Appointed by the client where more than one contractor is involved. Plans, manages, monitors and coordinates the pre-construction phase. Must have skills, knowledge and experience to understand the design and how it can be built safely. Can be the architect, structural engineer, or an experienced trades contractor on smaller projects.

3. Principal Contractor (PC): Appointed by the client where more than one contractor is involved. Plans, manages, monitors and coordinates the construction phase. Produces and maintains the Construction Phase Plan. Manages site security, welfare, and safe working. Can be the main contractor or lead tradesperson.

4. Designer: Anyone who prepares or modifies design information. This includes architects, engineers, and trades contractors who design elements of their own scope (a plumber designing a mechanical installation is a designer under CDM).

5. Contractor: Anyone carrying out construction work, including self-employed trades. Must: plan and manage their own work; use the Construction Phase Plan; cooperate with the PC; not create risk for others.

When are PD and PC required? Where more than one contractor is involved (including the client themselves if they are a business). For domestic clients (homeowners) with a single contractor: less formal; CDM still applies but duty holder roles overlap.

F10 notification: For notifiable projects (>30 working days with >20 workers simultaneously, OR >500 person-days), the PC must notify the HSE via the F10 form before construction starts. This is an online submission at HSE's website.

Construction Phase Plan: Required for all projects with more than one contractor. The PC prepares it before work starts. Content includes: project description; management arrangements; site rules; emergency procedures; welfare facilities; specific risk controls.

Health and Safety File: Required for projects with more than one contractor. Created by the PD during design; maintained and updated by the PC during construction; handed to the client at completion. Contains information about the completed building relevant to future work (as-built drawings, materials used, dangerous locations).

Commercial Electrical Standards

Commercial electrical installations follow BS 7671 as the underpinning standard, but the application differs significantly from domestic:

Distribution:

• Commercial installations typically have a three-phase 400V supply (TN-S or TN-C-S)
• Sub-distribution boards fed from a main LV distribution board
• Bus-bar trunking for large current ratings
• Cable management: containment (tray, trunking, conduit) is mandatory in most commercial environments
• No clipping to surface with oval conduit clips — proper containment required

Cable types:

• SWA (steel wire armoured): BS 5467 or BS 6724; the armour is the circuit protective conductor
• FP200 or equivalent fire-performance cables for emergency lighting and fire alarm circuits
• MICC (mineral insulated copper clad): fire-resistant circuits; requires specialist termination tools
• BASEC-certified cables generally expected for commercial

Emergency lighting:

• Required by Building Regulations Part B and BS 5266-1 in commercial premises
• Must be maintained and logged; annual service and periodic testing

Fire alarm systems:

• BS 5839-1 is the design, installation and commissioning standard
• Category L systems (life protection), P systems (property protection)
• Commercial premises above basic threshold require formal fire alarm system

EICR frequency in commercial:

• No legal universal standard, but:
• Offices, hotels: every 5 years
• Schools: 5 years
• Pubs, bars, restaurants: every 1–5 years depending on conditions
• Industrial: annually or more

Commercial Gas: IGEM Standards

Gas Safe registration is still required for commercial gas work, but additional IGEM (Institution of Gas Engineers and Managers) standards apply:

Key commercial IGEM standards:

• IGEM UP/1A — Tightness testing for commercial/industrial installations
• IGEM UP/2 — Installation pipework on industrial and commercial premises
• IGEM UP/10 — Handling of gas emergencies (as applies to commercial)
• IGEM UP/11 — Gas installations for educational establishments
• IGEM UP/19 — Commercial catering installations

Commercial catering gas: Installing or servicing commercial catering appliances (range cookers, fryers, steam ovens, combi ovens) requires:

• Understanding of IGEM/UP/19
• Knowledge of commercial appliance categories and gas rates
• Understanding of canopy and extract requirements (usually a separate M&E scope)
• Specific knowledge of commercial flexible connections and shut-off systems

Pressure and flow testing: Commercial gas installations must be tightness-tested to IGEM UP/1A which has different procedures from the domestic IGEM UP/1B. Pressure test pressures and test duration differ, and the system must be purged before commissioning.

Contractor Assessments: Getting on Approved Lists

Commercial clients, facilities managers and local authorities typically require contractors to demonstrate competency before they are awarded work. The main schemes in the UK:

Constructionline:

• Government-owned, operated by Capita
• Three tiers: Standard, Silver, Gold
• Gold level includes PAS 91 pre-qualification; covers: health and safety, environmental, quality, equality and diversity
• Annual subscription; approximately £175–£500 per year depending on turnover
• Very commonly requested by local authorities and housing associations

CHAS (Contractors Health and Safety Assessment Scheme):

• Health and safety focused
• Annual assessment; submission of policies, risk assessments, accident records
• More focused on H&S compliance than Constructionline
• Often required alongside Constructionline

SafeContractor:

• Alcumus-run alternative to CHAS
• Health and safety assessment; similar scope to CHAS
• Mutually recognised with CHAS in some procurement frameworks

ISO 9001:

• Quality management systems standard
• Shows systematic approach to quality; more demanding to achieve than Constructionline/CHAS
• Required for some larger frameworks (main contractors, public sector supply chains)

RAMS (Risk Assessments and Method Statements): Commercial clients almost universally require RAMS before allowing work to start. Typically:

• Generic RAMS for standard operations (electrical installation, plumbing, etc.)
• Site-specific RAMS for complex or hazardous activities
• RAMS reviewed and signed off by the client's facilities manager or H&S advisor before access is granted

Commercial vs Domestic: Building Regulations Differences

The same Building Regulations parts apply to commercial as domestic, but the occupancy class changes what is required:

Part B (Fire Safety):

• Commercial premises have occupancy classifications under BS 9999 (or BS 9991 for residential)
• Higher-risk occupancies (public access, sleeping accommodation) require more robust fire protection
• Sprinkler systems may be required
• Compartmentation requirements are more stringent
• Fire safety strategy often required from a fire engineer

Part M (Access):

• Commercial buildings open to the public must be accessible to disabled people
• New or substantially renovated commercial buildings must comply with Part M: suitable entrance widths, accessible toilets, step-free access
• This is a common issue with commercial refurbishments — any "material alteration" triggers Part M

Part F (Ventilation):

• Commercial kitchen ventilation is complex: IGEM UP/19, local exhaust ventilation for hazardous substances (COSHH), and DW172 from the Heating and Ventilating Contractors Association (HVCA)
• ASHRAE 62.1 or CIBSE Guide A for commercial ventilation design

Frequently Asked Questions

I'm a domestic plasterer — can I take on commercial plastering work?

Technically yes — plastering is plastering. But commercial work typically requires:

• Evidence of liability insurance with higher limits (£2M+ PLI minimum; some clients require £5M+)
• RAMS preparation
• Potentially Constructionline or CHAS registration if working for a large client
• IPAF if working at height on powered access equipment
• Understanding of CDM obligations as a contractor

If you are planning to move into commercial work, getting Constructionline Standard registration and a CHAS assessment is the first step — it opens doors with commercial clients who won't engage without these.

What insurance do I need for commercial work?

For domestic work, £1M–£2M public liability insurance is standard. For commercial:

• Public liability: typically £5M minimum; some major clients require £10M
• Employers' liability: £10M (legally required if you have any employees, including part-time)
• Professional indemnity: required if you design as well as install (e.g. specifying a system)
• Products liability: important if you supply goods that could cause harm

Check your current policy exclusions carefully — some domestic PLI policies exclude commercial premises entirely.

Do I need CSCS card for commercial work?

The Construction Skills Certification Scheme (CSCS) card is not legally mandatory, but almost all large commercial sites require a CSCS card for site access. There are different card types based on qualifications:

• Skilled Worker: completed a relevant NVQ Level 2/3
• Technician: HNC/HND or equivalent
• Academically/Technically Qualified Person: degree level
• Gold Card: NVQ Level 3 + site supervisor or manager qualification

If you plan to work on commercial sites, get the appropriate CSCS card. The application requires evidence of qualification and a health and safety test.

Regulations & Standards

• Construction (Design and Management) Regulations 2015 (SI 2015/51) — CDM 2015

• Health and Safety at Work etc. Act 1974 — overarching safety duty

• Building Regulations (England and Wales) — all parts apply to commercial; check occupancy classification

• Regulatory Reform (Fire Safety) Order 2005 — fire risk assessment in commercial premises

• BS 7671:2018+A2:2022 — Wiring Regulations (commercial electrical)

• BS 5839-1:2017 — Fire detection and alarm systems: design, installation and commissioning

• BS 5266-1:2016 — Emergency lighting: code of practice

• PAS 91:2013+A1:2017 — Pre-qualification questionnaire for contractors

• HSE CDM 2015 Guidance — Full CDM 2015 guidance including duty holder responsibilities

• Constructionline — Contractor registration and assessment

• CHAS — Contractor health and safety assessment

• subcontracting — CIS and tax obligations when subcontracting on commercial sites

• ppe selection — PPE and risk management for commercial site work