Every subcontractor has been there. You price a job carefully, win the work, mobilise — and then discover that something you assumed was excluded is sitting squarely in your scope. Not as an instruction. Not as a variation. Just there, written into the subcontract documents in language that, when read carefully, leaves no room for argument.
Scope gaps are one of the most common — and least discussed — causes of subcontractor losses in UK construction. They accumulate quietly, buried in definitions, referenced documents, and the ambiguous space between what a tender describes and what a subcontract requires. By the time the gap becomes visible, you're often committed to carrying the cost.
This post explains what scope gaps are, how they arise, where they're most likely to appear, and what the financial consequences look like. It also covers what to look for before you sign — because the gap is always easier to close at tender stage than after you've mobilised.
What Is a Scope Gap?
A scope gap is the difference between what a subcontractor priced and what the subcontract actually requires them to deliver. It sounds simple, but in practice it can arise in several distinct ways.
The most straightforward version is a genuine omission — something that needed to be included in the pricing was missed entirely, either because it wasn't clearly described in the tender documents or because it was buried in a reference to another document that wasn't reviewed properly.
A more insidious version occurs when the subcontract documents expand the scope beyond what the tender enquiry described. The tender might specify "supply and install of X," while the subcontract incorporates an employer's requirements document that adds testing, commissioning, and as-built documentation to the same scope at no additional cost.
A third version arises from ambiguity rather than outright omission — where the scope could reasonably be read either way, and the main contractor takes the interpretation that puts more cost on you. Without clear contractual language excluding the disputed item, the argument is hard to win.
All three versions have the same practical result: work gets done that wasn't priced, and recovery is either impossible or disproportionately costly to pursue. LazyQS tender pack review flags scope ambiguity during tender and contract review, cross-referencing what's described in the enquiry against what the subcontract documents actually require.
How Scope Gaps Arise
At Tender Stage
The tender stage is where most scope gaps are created. Under time pressure to price and submit, subcontractors often review the headline scope description without working through every supporting document. Employer's requirements, specification sections, drawing lists, and preliminary schedules all interact with the main scope — and all can contain obligations that don't appear anywhere in the tender summary.
Main contractors know this. Tender packs are frequently structured in ways that make comprehensive review genuinely difficult: large volumes of documents, cross-references between different sections, last-minute addenda issued close to the tender return date. This isn't always deliberate, but the effect is the same — subcontractors price on an incomplete picture of what's actually required. Our guide on how to review a tender pack as a subcontractor covers how to approach this process systematically.
Another common source of tender-stage gaps is the gap between a performance specification and a prescriptive one. When a tender asks for a system that "achieves X performance," it's easy to price a solution that meets the requirement under expected conditions. But if the specification document (which you may not have read in full) requires specific components, installation methods, or testing regimes, your priced solution may not comply — and bringing it into compliance costs money you didn't budget.
At Contract Stage
Even where the tender review was thorough, the subcontract itself can introduce new scope. This happens in several ways.
The most common is the incorporation of documents that weren't included in the tender pack. Employer's requirements, BIM protocols, method statements, and health and safety plans regularly appear in the "Contract Documents" schedule of a subcontract without having been provided during tendering. By accepting the subcontract, you're agreeing to comply with documents you've never seen.
A related issue arises from revision control. Drawings and specifications issued with the subcontract are sometimes later revisions than those used for pricing. If the revision is not flagged and the additional scope isn't valued as a variation, you carry the cost of the difference.
Finally, subcontract conditions themselves can expand scope through definitions. Terms like "the Works," "the Sub-Contract Documents," and "design obligations" are defined in the conditions — and those definitions can be broader than you'd expect. A subcontract that defines "the Works" to include all items "necessary for the proper completion" of the specified works is doing something very specific: it's loading latent scope obligations onto you that go beyond what was described.
Manually searching a 200-page tender pack for scope gaps takes hours. LazyQS cross-references your tender enquiry against the subcontract documents and flags mismatches automatically — with page references — in under 30 minutes.
Where Scope Gaps Are Most Likely to Appear
Preliminaries and Site Costs
Preliminaries — the costs of being on site rather than the costs of the work itself — are a consistent source of scope gaps. A subcontract may include obligations for site accommodation, welfare, hoarding, temporary power, or security that the subcontractor assumed were being provided by the main contractor.
Even where the main contractor is providing these facilities, the subcontract may require a contribution to their cost. These contribution obligations are sometimes buried in the preliminaries schedule or in a project-specific annex rather than the main scope description — which means they're easy to miss and equally easy to dispute once the project is underway.
Temporary Works
Temporary works — propping, shoring, access scaffolding, falsework — are an area where scope ambiguity is particularly expensive. They're not always listed as a discrete line item in a tender, and responsibility for them is frequently unclear in both the tender documents and the subcontract.
If the subcontract imposes a design obligation that encompasses the permanent works, it may also — depending on how the scope is drafted — extend to the temporary works needed to install them. That can be a substantial and unpriced liability, particularly on structural or mechanical and electrical packages where temporary support arrangements are complex.
Design Obligations
Design scope gaps are among the most financially significant because they carry both direct cost (the resource required to produce the design) and liability implications. A subcontract that was tendered on the basis of "install to contractor's design" becomes a very different animal if the subcontract documents impose a design obligation — particularly if that obligation includes fitness for purpose rather than reasonable skill and care. Our post on unfair subcontract clauses covers design liability in more detail.
Design scope gaps also arise from coordination obligations. Even where the primary design is clearly the main contractor's responsibility, subcontracts frequently impose obligations to "check and verify" design information received, to flag clashes, and to integrate with other trade designs. These obligations have a cost that is rarely priced at tender.
Testing, Commissioning, and Documentation
Testing and commissioning requirements are regularly underestimated in subcontract pricing, and the gap between what's tendered and what's required is often significant. Specifications may require multiple testing regimes, witnessed tests, specialist commissioning engineers, and extended soak periods that the subcontractor didn't price because these requirements were buried in a specification section they didn't review fully.
Documentation — O&M manuals, as-built drawings, warranties, BIM deliverables — is a similar issue. The obligation to produce these items is frequently clear in the specification but absent from the tender summary, and main contractors are increasingly stringent about withholding final retention until the full documentation package is delivered.
M&E subcontractors are particularly exposed in this area; our tender review checklist for M&E subcontractors covers testing and commissioning scope in detail.
The Cost Implications
Individually, any one scope gap might be manageable. Cumulatively, across a project, they can be devastating.
The direct cost is the most obvious element — resource deployed on work that wasn't priced. But there are indirect costs too: the management time spent arguing about scope, the impact on programme when unpriced work delays the completion of priced work, and the damage to the relationship with the main contractor when the dispute eventually surfaces.
There's also the opportunity cost of pursuing recovery. Variation claims based on scope gaps require evidence — a clear demarcation between what was included and what wasn't, a pricing base for the additional work, and the contractual entitlement to value it at all. Where the scope was genuinely ambiguous, that entitlement is often contested — and pursuing a dispute through adjudication can cost more than the scope gap itself is worth.
The most expensive scope gaps are the ones that aren't identified until late in a project, when it's no longer possible to manage the cost. A gap identified at contract review stage, before mobilisation, can be addressed through a pre-construction query, a clarification letter, or a negotiated adjustment to the subcontract price. A gap identified on site, six months into the project, is almost always absorbed.
Scope Gap Identification Checklist
Before signing your subcontract, work through these checks:
- Referenced documents — Have you obtained and read every document listed in the Contract Documents schedule? Request any that weren't included in the tender pack before signing.
- Scope definitions — How is "the Works" defined? Does the definition extend to items "necessary for completion" or similar catch-all language?
- Revision control — Are the drawings and specifications in the subcontract the same revision as those used for pricing? If not, have the changes been valued?
- Preliminaries — Are there any obligations to provide or contribute to site facilities, welfare, or temporary services that you haven't priced?
- Temporary works — Does your design obligation extend to temporary works? Is responsibility for temporary works design explicitly allocated?
- Design standard — Is the design obligation reasonable skill and care or fitness for purpose? Does your PI cover respond?
- Testing and commissioning — Have you read the full testing specification, not just the scope summary? Are witness test and soak period requirements priced?
- Documentation — What O&M, as-built, and BIM deliverables are required? Are these priced and resourced?
- Coordination obligations — Are there obligations to check, verify, or integrate design information from other parties? What does compliance with these obligations actually require?
- Employer's requirements — Have you been provided with the full employer's requirements? Do they contain obligations that don't appear in the tender scope?
How to Protect Yourself
The most effective protection against scope gaps is time — time to read the documents properly before pricing, and time to review the subcontract carefully before signing. In a competitive tender environment, both are in short supply. That makes a systematic approach essential.
At tender stage, a disciplined document review that works through every item in the tender pack — rather than relying on the scope summary alone — will catch most gaps before they're priced in. Where there's genuine ambiguity, a pre-tender query to the main contractor creates a record of the uncertainty and forces a clarification that becomes part of the tender basis.
At contract stage, the same discipline applies to the subcontract documents. Check the Contract Documents schedule against the tender pack. Identify any documents that weren't provided at tender. Request them. Review revision numbers on drawings and specifications. Check scope definitions in the conditions.
Where gaps are identified at contract stage, raise them before signing — not after. A letter or email flagging the issue and proposing either a scope clarification or a price adjustment creates a record that's far more useful than an unanswered query raised after mobilisation. If the main contractor won't engage, that's important commercial information in itself.
Systematic contract review is exactly what LazyQS tender pack review is built for — cross-referencing scope documents, flagging ambiguity, and identifying the gaps that are easy to miss under time pressure. Catching a scope gap before you sign is almost always cheaper than carrying it through a project.