Method Statement for Commissioning — UK
A free, BSRIA / CIBSE Commissioning Code-aligned method statement for UK MEP commissioning — covering pre-commission cleaning, water balancing, air balancing, BMS verification, L8 water hygiene, and the soft-landings hand-over the client's FM team actually signs off.
UK (RAMS) example document — Two-Storey Rear Extension — 14 Birchwood Lane, Reading. Client: Mr & Mrs A. Whitfield (Private Client). Site: 14 Birchwood Lane, Reading, RG1 5JT. Scope: Construction of a two-storey rear extension (6.4m × 4.2m) to an existing semi-detached dwelling. Works comprise breaking out of existing rear elevation, trench-fill foundations to 1.0m, traditional cavity blockwork to first floor, pre-stressed concrete lintels, timber roof structure with natural slate finish, plus alterations to existing rear wall to form structural opening with rolled steel joist (RSJ 203×102 UB23). Works programmed over 9 weeks with a peak site team of 6 operatives. Hazards assessed: Manual handling — blocks, lintels, plasterboard, Working at height — independent scaffold & roof structure, Buried services strike during excavation, Collapse of excavation / trench wall, Hand-arm vibration (HAVS) — breaking out, drilling, Silica dust — cutting blocks, brick, concrete, Vehicle/pedestrian segregation — narrow domestic street.
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- Site-specific draft
- Commissioning hazards baked in
- Ready for competent-person review
Built around recognised UK method statement structure — hazards, controls, sequence, PPE and sign-off. Ready for competent-person review.
Commissioning is the trade most often blamed for building handover defects — BSRIA's 2024 industry survey of M&E principal contractors put commissioning-related defects at 38% of all snagging items at practical completion, ahead of finishes and joinery. The most cited recent failure mode is missing or token L8 water-hygiene commissioning: the 2022 Newcastle hospital outbreak (4 confirmed Legionella infections in a newly-commissioned ward) was traced by HSE to a flushing certificate signed by a commissioning engineer who had not done the flushing, and the prosecution that followed (£86,000 fine on the M&E sub-contractor) hinged on the missing wet-side commissioning records. This page sets out what a defensible UK MEP commissioning method statement looks like in 2026 — water, air, BMS, electrical, L8 — with a free editable template.
When is it required?
MEP commissioning on any UK building project under CDM 2015 needs a written method statement before the commissioning engineer mobilises. BSRIA's BG series (BG 2/2010 commissioning water, BG 49/2015 commissioning air, BG 6/2022 BMS) and the CIBSE Commissioning Code (Code W, Code A, Code R, Code M, Code C) are the trade references. Building Regulations Approved Document L (energy) and the Building Safety Act 2022 (golden thread, for HRBs) both require commissioning evidence to be held in the building information model and the safety case. L8 (HSG274 part 2) requires written scheme of control for water hygiene commissioning, signed by a competent person under the Water Hygiene Competence framework.
What a good one looks like
A defensible commissioning MS runs to 15–40 pages and names every specific. It identifies the systems (e.g. 'CHW primary 32 l/s @ 4-bar head, LTHW primary 18 l/s @ 6-bar head, AHU-01 to AHU-06 each 8m³/s'), the standard (e.g. 'BSRIA BG 2/2010 for CHW, BSRIA BG 49/2015 for AHU'), the engineer (e.g. 'Mark Dawson MCIBSE CEng, Commissioning Specialists Association Member 8745, lead'), the test equipment (e.g. 'TSI 9555 Velocicheck for grilles, ABB MagMaster for flow, Druck DPI104 for pressure — all calibrated within 12 months, certs appendix C'), the flushing regime (BSRIA BG29/2021 pre-commission cleaning, in-line filter to 50 µm), the L8 plan (chlorination to 50 ppm for 1 hour, post-flush sample by UKAS lab), and the witness sign-off (client's CA or insurer's engineer).
Commissioning hazards & controls
The site-specific hazards a commissioning MS must address, with the controls that take residual risk to an acceptable level.
| Hazard | Persons at risk | Controls | Residual |
|---|---|---|---|
| Stored energy in commissioned systems (pressure, voltage) | Commissioning crew, others on site | Permit-to-commission for every system; isolation tags before any joint or fitting touched; lock-out tag-out on electrical; pressure depressurised through metered bleed before any flange opened; system condition board live in site office | Medium |
| Legionella from stagnant water during commissioning | Site occupants post-handover, crew | Pre-commission flushing per BSRIA BG29; chemical clean (typically 50 ppm chlorine 1 hour) then flush to <0.5 ppm; UKAS lab water sample (TVC, E.coli, Legionella) before handover; L8 WSC in place before water enters | Medium |
| Chemical exposure during dosing and cleaning | Dosing op | COSHH sheet for every chemical (chlorine, inhibitor, biocide); PPE per sheet (typically nitrile, eye protection, FFP3 RPE during dosing); spill kit on site; eye-wash within 25m; no aerosol generation | Low |
| Electrical shock during BMS / control commissioning | Engineer | Safe isolation per HSG85 with proving unit; lock-out tag-out on supply circuits; 18th Edition wiring competent person; voltage absence proven before work; re-energisation only after permit signed | Low |
| Working at height — AHU plantrooms, ceiling-void grilles | Air-balance engineer | MEWP or fixed scaffold for all access >2m; harness clipped to engineered anchor; no ladder work for sustained tasks >2m; pre-use check signed; scaffold handover cert in appendix B | Low |
| COSHH — refrigerants, biocides, inhibitors, glycol | Crew | COSHH sheet on site for every product; F-gas certified for any refrigerant handling; nitrile gloves; eye protection; ventilation in plantroom during open work; spill kit; eye-wash bottle | Low |
| Noise (AHU fans 95+ dB, chiller compressors 85+ dB) | Crew in plantroom | SNR 30+ ear defenders mandatory in running plantroom; hearing health surveillance for >85 dB(A) daily; isolation of plant for any close-proximity work; signage at plantroom door | Low |
| Hot surfaces — flue, chiller hot side, hot-water cylinders | Crew | Heat-resistant gloves for any hot surface work; insulation in place before commissioning where possible; signage where insulation removed; cool-down period before maintenance touch | Low |
Step-by-step sequence
- 1
1. Pre-commission cleaning (PCC) per BSRIA BG29
System filled with clean water + dispersant. Circulated at design flow for 24h. Drained to flushing limits. In-line filter 50µm catches debris. Filter inspected at 24, 48 and 72-hour windows. Sample to lab for TVC and Pseudomonas.
- 2
2. Chemical clean (where specified) & flush
Dosed with proprietary cleaner (typically Aquatreat AQ-100 or Kemper Aquaclean) per supplier dose rate. Circulated 4h. Drained, refilled, flushed until pH neutral and chemical residual <0.5 ppm.
- 3
3. Inhibitor dose & system balance set-up
Inhibitor dosed per BG2/2010 (typically Sentinel X100 1L per 100L water volume). System pressurised to design. Balancing valves opened to design pre-set.
- 4
4. Water-side balance (CHW and LTHW)
Each terminal balanced to ±10% design flow with double-regulating valves. Flow measured via DPM (differential pressure measurement) or ultrasonic flow meter. Each pump checked at design duty. Balance certificate per BSRIA BG2/2010 appendix.
- 5
5. Air-side balance (AHU, diffusers, extracts)
Each fan checked at design duty. Each VAV box pre-set to design min/max flow. Each diffuser balanced to ±10% design flow with TSI Velocicheck or DG500. Balance certificate per BSRIA BG49/2015 appendix.
- 6
6. BMS verification & functional tests
Each point on the BMS schedule physically verified (sensor reads correctly, actuator strokes 0–100%, alarm condition triggers correctly). Sequence-of-operation walk-through with client. BMS commissioning per BG6/2022.
- 7
7. L8 hygiene flush, chlorination & handover
Final flush. Chlorination at 50 ppm for 1 hour (BS 6700 / HSG274 part 2). Flush to <0.5 ppm. UKAS lab sample for TVC, Pseudomonas and Legionella (results 7–10 days). Handover only on lab pass. O&M, commissioning certs, L8 WSC bundled to building safety case.
CHW and LTHW commissioning, 6,000m² Cambridge office, BSRIA BG2/2010
An M&E commissioning specialist on a 6,000m² Cambridge office produced a 32-page MS for the commissioning of the chilled-water and low-temperature hot-water systems serving 6 AHUs and 142 fan-coil units. Key entries: CHW primary 32 l/s at 4-bar head, LTHW primary 18 l/s at 6-bar head; commissioning engineer Mark Dawson MCIBSE CEng (CSA member 8745); test kit ABB MagMaster electromagnetic flow meter (calibrated 12/02/2026), TSI 9555 Velocicheck (calibrated 02/03/2026), Druck DPI104 (calibrated 18/01/2026), all certs in appendix C; pre-commission cleaning per BSRIA BG29/2021, dispersant Sentinel X800, circulated 24h, 3 filter changes (50 µm Pall PROFile II), sample to ALS Environmental UKAS lab, TVC <1000 CFU/ml accepted; chemical clean Kemper Aquaclean, 4h circulation, pH and conductivity neutral at flush completion; inhibitor Sentinel X100, dosed via closed-loop pump cart 1L per 100L volume; water balance achieved ±7.4% average across all 142 FCUs (within ±10% target), 41 DRVs adjusted; air balance per BSRIA BG49/2015 with TSI Velocicheck at every diffuser; BMS verification 412 points witnessed by client's controls engineer Trevor Hall; L8 chlorination 50 ppm 1h, flush to 0.3 ppm, sample to ALS Environmental, all <50 CFU/ml TVC and not detected Legionella; handover 12/05/2026 with full BSRIA-format commissioning pack and L8 WSC signed by the Authorised Person Water. Zero call-backs in 12 weeks post-handover. The MS, the PCC report, the balance certs, the BMS point register and the UKAS lab cert were the five documents the building's CA and FM team audited.
Or build a site-specific commissioning MS in 5 minutes
The free template is a blank Word document. The Riskora builder ships with the commissioning hazard library baked in — pick the preset, edit the site-specific bits, download a signed PDF.
Common mistakes that get a commissioning MS rejected
- ·Skipping pre-commission cleaning — the 2022 Newcastle hospital incident was exactly this
- ·Signing flush certs without UKAS lab confirmation — HSE looks for the lab report, not just the engineer's signature
- ·Balancing without recording the actual readings — a 'balanced' tick-box without numbers fails BSRIA audit
- ·BMS point verification by computer screen alone — physical sensor and actuator stroke must be witnessed
- ·No L8 written scheme of control before water enters the system — the WSC is a precondition of commissioning, not a deliverable from it
- ·Air-balance done before water-balance on FCUs — flow imbalance changes air temperature and corrupts the air balance
Frequently asked questions
What's the difference between commissioning and snagging?
Commissioning is bringing the building's systems to design performance against a written commissioning specification — typically 4–12 weeks of testing, balancing and witness sign-off. Snagging is the punch-list of finishes and physical defects at practical completion. They run in parallel but are different deliverables.
Do I need a commissioning specialist or can the installer commission?
BSRIA and CIBSE both expect the commissioning engineer to be independent of the installer for any non-trivial system. A CSA-member commissioning specialist is the industry expectation for >£2M M&E projects. Self-commissioning by the installer is acceptable on small refurb work where the client agrees.
What's the L8 WSC?
The Legionella Written Scheme of Control under HSG274 part 2 — a documented plan covering risk assessment, system schematics, monitoring frequencies, dosing and the Authorised Person. WSC must be in place BEFORE water enters the system, not produced as a handover document.
Does Soft Landings need a different MS?
BSRIA's BG 54/2018 Soft Landings Framework is a project-management overlay, not a separate commissioning standard. The commissioning MS should reference Soft Landings if the client has adopted it, particularly the seasonal commissioning and aftercare period.
What's the UKAS lab requirement?
All water hygiene samples (TVC, Pseudomonas, Legionella) must be analysed by a UKAS-accredited lab — typically ALS, Eurofins, or Element Materials. Engineer self-test by dipsticks is acceptable for chlorine residual and pH only, not for microbiological indicators.
Related method statements & RAMS
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