Mechanical and electrical subcontractors face risks at tender stage that most general subcontractors never encounter. The scope is technically complex, the design responsibilities are often blurred, and the commissioning obligations can carry significant cost exposure that only becomes apparent once work is underway. By then, the price is fixed and the programme is running.
A thorough tender review is the only reliable defence. It won't eliminate risk, but it will ensure you understand what you're pricing — and what you're not. This checklist is written specifically for M&E subcontractors working on UK construction projects. If you haven't already looked at the general guide to reviewing a tender pack as a subcontractor, that's a useful starting point before working through the M&E-specific considerations below.
Design Responsibility
Who Owns the Design
M&E subcontracts frequently contain ambiguous design responsibility. The tender documents may describe a "performance specification" — setting out what the system must achieve — and leave the design of the solution entirely to you. Or they may provide partial drawings and specifications that appear complete but leave coordination and detailed design to be resolved during the works. Neither situation is unusual. Both carry significant risk if you don't understand the extent of your obligation before you price.
Check whether the subcontract imposes a fitness-for-purpose design obligation or a reasonable skill and care standard. Fitness for purpose means the installed system must achieve the stated performance outcome, regardless of whether you acted competently. Most professional indemnity policies cover reasonable skill and care claims and exclude fitness for purpose explicitly. If you're accepting fitness-for-purpose liability, you need to know before you price — because your insurance may not respond if something goes wrong.
Check also whether the design obligation flows down from the employer's requirements. If the main contractor is carrying a fitness-for-purpose obligation upstream and has passed it to you by reference, you may be exposed without realising it. Buried cross-references to other documents are one of the most common sources of unexpected design liability in M&E subcontracts.
Performance Specifications
Performance specifications state what a system must deliver — airflow rates, lux levels, temperature ranges, acoustic performance — without specifying exactly how it must be achieved. They give you flexibility but transfer the design risk entirely onto your price. The system must hit the stated performance targets, and if it doesn't, you're responsible for remedying it regardless of cost.
Before pricing against a performance specification, confirm that the targets are achievable within the space and infrastructure constraints described, that the commissioning requirements and handover evidence are clearly defined, and that you have enough information to design a compliant solution before committing to a fixed price. If you don't, your tender should either be conditional or should include a design allowance that reflects the actual uncertainty.
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Coordination Obligations
BIM and Drawing Coordination
On most modern commercial projects, M&E subcontractors are expected to contribute to a federated BIM model and produce coordinated installation drawings before work begins on site. The extent of this obligation — and who bears the cost of achieving coordination — varies considerably between tender packages.
Check whether the tender documents specify a BIM Level of Detail requirement, who is responsible for managing clash detection and resolution, and what the process is for instructed changes that result from coordination. Coordination is not free. If the scope requires you to redesign around other trades or resolve clashes that existed before you were appointed, that should be priced — or the responsibility for those changes should be clearly allocated elsewhere.
Scope gaps in M&E subcontracts are disproportionately likely to emerge through coordination — works that nobody specified, that sit between trades, and that the programme can't afford to argue about on site. The guide to scope gaps in subcontracts covers how these gaps arise and why they're so difficult to recover commercially once the programme is moving.
Interface with Other Trades
Check how the subcontract deals with interfaces between M&E works and other trades: builders' work in connection (BWIC), containment, supports, and penetrations. BWIC is a persistent source of dispute — it's often unclear whether it falls within the M&E subcontract, the builder's contract, or a separate specialist package. If BWIC is included in your scope, ensure the pricing documents include an adequate allowance and that the extent is clearly defined.
Similarly, check who is responsible for providing containment and support systems for your installations. Cable tray, conduit, pipe supports, and hangers represent real cost. If the tender documents describe a performance outcome without specifying who supplies the support infrastructure, assume you're being asked to include it.
Testing and Commissioning
Scope of Commissioning Obligations
Testing and commissioning (T&C) is one of the highest-risk elements of an M&E tender. It requires coordination across trades and disciplines, it happens at the end of the programme when pressure is highest, and it can generate significant additional cost if the scope is poorly defined or if systems can't be commissioned on time because of factors outside your control.
Check what the commissioning scope actually includes. Functional testing, system integration, performance verification, witnessing by the employer or contract administrator, and production of O&M documentation all fall under "commissioning" in some contracts. Each has a different cost profile. A scope that describes commissioning in general terms and leaves the detail to be agreed later is a commercial risk that belongs in your tender qualifications.
Check also who bears the cost of abortive commissioning. If systems need to be re-tested because of delays caused by other trades, because the building isn't ready, or because the employer changes the commissioning programme, are those costs recoverable? Without a clear mechanism for claiming additional commissioning costs, you'll be carrying them.
Seasonal and Extended Commissioning
Heating, ventilation, and air conditioning systems frequently require seasonal commissioning — testing the heating in winter and the cooling in summer — to demonstrate full performance. If your subcontract requires seasonal commissioning, this extends your obligations (and your retention) well beyond the normal completion date.
Check whether seasonal commissioning is a contract requirement, how long it extends your liability, and whether retention is held until seasonal commissioning is signed off. Retention held for an additional 12 months while you return to site for seasonal testing is a material cash flow consideration that should be reflected in your price. If this obligation exists but wasn't clearly flagged in the tender documents, flag it in your tender return.
Provisional Sums and Undefined Work
Identifying Provisional Sums
Provisional sums — budget allowances for work not yet fully defined — are a regular feature of M&E tender packages. They appear in bills of quantities or pricing schedules and are intended to cover scope that will be instructed and valued later. The problem is that provisional sums are often set at unrealistically low levels, they may attract lower margin than you'd price for fully defined work, and the process for converting them into instructed works (and recovering your actual costs) isn't always clear.
Before pricing, identify every provisional sum in the tender documents and consider what it's likely to cover. If a provisional sum is clearly insufficient for the scope it's intended to address, note this in your tender. If the mechanism for converting provisional sums into instructions is vague, ask for clarification before you submit.
Check also whether the contract entitles you to recover prelims and overhead on provisional sum expenditure in the same way as on measured work. Some contracts restrict the uplift applicable to varied and provisional works, which can erode margin significantly on projects where a large proportion of the scope is undefined at tender stage.
Attendance and Unspecified Obligations
M&E tender packages sometimes include attendance obligations — requirements to provide access, unload and distribute materials, or assist other trades — that aren't reflected in the pricing documents. These may appear in a preliminaries section or buried in the specification. They represent real resource cost.
Read the preliminaries and specification in full before finalising your price. If attendance obligations are present and unpriced, either include a cost allowance or exclude them explicitly in your tender qualifications. Discovering an unpriced attendance obligation after award is uncomfortable. Discovering it during the programme is worse.
M&E Tender Review Checklist
- Design Responsibility — Is the design obligation fitness for purpose or reasonable skill and care? Does your PI policy respond to the standard imposed?
- Performance Specifications — Are performance targets clearly stated and achievable within the described constraints? Is the commissioning evidence required to demonstrate compliance defined?
- Design Document References — Have you reviewed every document referenced in the scope? Are there cross-references that import obligations from other contracts?
- BIM and Coordination — What is the Level of Detail required? Who manages clash detection and resolution? Are coordination costs included in the scope?
- BWIC and Interface Works — Is builders' work in connection included in your scope? Who provides supports, containment, and hangers?
- Commissioning Scope — What does commissioning include? Who witnesses? What documentation is required at handover?
- Abortive Commissioning — Is there a mechanism to recover costs of re-testing caused by factors outside your control?
- Seasonal Commissioning — Is seasonal testing required? How long does it extend your obligations and retention?
- Provisional Sums — Have you identified every provisional sum? Are the allowances realistic? What uplift applies to instructed provisional works?
- Attendance Obligations — Are there unpriced attendance requirements in the preliminaries or specification?
- Programme and Sectional Completion — Are there multiple sections with separate completion dates? Does your works programme align with access commitments?
- Liquidated Damages — Are LDs capped and proportionate to your subcontract value? Do they apply only to delay attributable to your works?
Putting the Checklist to Use
A checklist is only useful if you have enough time and information to work through it properly. M&E tender packages are often issued with compressed return periods, and the technical volume — drawings, specifications, coordination notes, BIM requirements — can be substantial. The pressure to submit quickly is real. So is the cost of missing something.
The subcontractor contract review checklist covers the contract terms that sit alongside the technical scope. Both matter: a well-priced M&E tender can still carry serious commercial risk if the contract terms impose disproportionate liability, uncapped set-off, or unfair commissioning obligations. Review both the scope and the contract before you commit.
LazyQS tender pack review can accelerate this process. Upload your tender pack and get a structured risk analysis across scope, design responsibility, programme, and contract terms — so you go into any tender negotiation or qualification process knowing exactly where the risks sit and what to raise before you sign.
The goal of a tender review isn't to find reasons not to bid. It's to understand what you're pricing, surface the risks that should be priced or qualified, and make a clear-eyed decision about whether the work is worth pursuing on the terms offered. For M&E subcontractors, where the technical scope is complex and the commissioning tail can extend well beyond practical completion, that review is worth doing on every significant tender.