Valuation, Fair Pricing, and Practical Takeaways: Legal Issues
The mandatory Clause 10.6 valuation hierarchy governs adjustments to the contract sum, with fair valuation and quantum meruit available only as residual remedies for employers and Employer’s Representatives (ERs).
Introduction
In Part 1 of this series, we examined the conceptual framework for variations, the elements of a valid variation, the valuation starting position, and the claims procedure, which serves as the gateway to valuation. Part 2 examines the mandatory Clause 10.6 valuation hierarchy, cost-based valuation, the residual remedies of fair valuation and quantum meruit, preliminary overheads, and practical takeaways for employers and ERs.
The Clause 10.6 Valuation Hierarchy
Three preliminary points should be noted. First, the term “substituted” work in Clause 10.6 should be interpreted broadly to include any change to the nature or character of the works arising from a compensation event. Second, works that were originally planned based on full design information and identified contractor risk can be radically altered by the nature and timing of compensation events. Employers and ERs should be alert to how those changes affect the assumptions underpinning the Pricing Document. Third, the valuation hierarchy set out in Clauses 10.6.1 to 10.6.4 is mandatory and must be applied in sequence. The employer should ensure that the ERs do not jump directly to a fair valuation without first applying the higher tiers.
This point is supported by the Wren commentary on the Public Works Contract (PWC), which notes that under Clause 10.6.1, the ERs have no discretion to depart from contract rates. The rationale was articulated in 2005 by the Court of Appeal (England and Wales), which held that opening up rates “would not only unsettle the basis of competitive tendering, but would also create the sort of uncertainty in the administration of building contracts which should be avoided at all costs.” There is an inherent tension here between the consequences of a unilateral mistake at the tender stage and the principle against unjust enrichment, but the hierarchy resolves that tension firmly in favour of contractual certainty.
Valuation Rules: Clauses 10.6.1 to 10.6.3
Clause 10.6.1 provides that where the varied work is of a similar character to work for which rates exist in the Pricing Document and is executed under similar conditions, those rates are to be used. Clause 10.6.2 applies where the work is not of a similar character or is not executed under similar conditions. In that case, the Pricing Document rates are used “when that is reasonable.” For employers, this reasonableness qualifier is a key point for scrutinising the evidential basis of any proposed star rate. The Wren commentary notes that valuation under Clause 10.6.2 requires the derivation of a “star rate.” In 2004, HHJ Thornton QC in the Technology and Construction Court (England and Wales) described such a rate as one “derived from sources outside the contract but sitting reasonably alongside existing contract rates.”
Clause 10.6.3 provides that where neither Clause 10.6.1 nor 10.6.2 applies, the ERs make a fair valuation based on rates for similar work in the locality. The Wren commentary identifies typical areas of contest under Clause 10.6.3: what constitutes “similar work,” what is meant by “the locality,” and what is “fair.” Employers and ERs should scrutinise those issues before accepting a fair valuation.
The mandatory nature of the hierarchy was confirmed by the Court of Appeal (England and Wales) in 2005. ) held that fair rates must reflect actual market conditions prevailing at the time the work is carried out. Where the contractual valuation mechanism cannot apply, a 2005 decision of the Technology and Construction Court (England and Wales) establishes that a fair valuation is to be substituted. Most disputes in practice arise at the boundary between Clauses 10.6.1 and 10.6.2, where the characterisation of work as “similar” or otherwise is determinative.
Cost-Based Valuation: Clause 10.6.4
Clause 10.6.4 provides an alternative cost-based method for valuing compensation events, available at the ERs’ election. It operates instead of the rate-based rules in Clauses 10.6.1 to 10.6.3. Employers should therefore understand when the election is available and ensure that the selected method is applied consistently.
Three cost heads are identified:
- Labour is valued at hours multiplied by the daily rate set out in Schedule 2E.
- Materials are valued at actual cost, net of discounts and exclusive of VAT, plus the percentage specified in Schedule 2E.
- Plant is valued at the rates set out in Schedule 1K, or at market rental rates plus the applicable percentage set out in Schedule 2E.
Accurate contemporaneous records are critical to any Clause 10.6.4 valuation. Employers should require and scrutinise those records, including the allocation of labour, material costs and plant usage, before accepting a cost-based adjustment.
The Wren commentary makes a structural point about Clause 10.6.4: the opening words “[i]nstead of sub-clauses 10.6.1, 10.6.2 and 10.6.3” suggest that the ERs must value the compensation event in full under Clause 10.6.4 without mixing elements from the other valuation routes. It is an all-or-nothing election. Notably, all discounts obtained from builders’ providers are for the employer’s benefit.
Fair Valuation and Quantum Meruit
The question of fair valuation arises where the contractual valuation mechanism has broken down entirely. Quantum meruit, literally, “what he deserves”, provides the residual remedy. In 1990, the Court of Appeal (England and Wales) held that quantum meruit arises where the contractual mechanism for valuation has broken down, and the court must determine a reasonable sum for the work carried out. In 2013, the Supreme Court (United Kingdom) confirmed that work is to be valued at the objective market rate, not by reference to the subjective benefit conferred on the recipient.
Fair valuation remains a residual remedy. The employer should ensure that the ERs exhaust the contractual hierarchy, comprising Clauses 10.6.1 through 10.6.3, before resorting to fair valuation or quantum meruit.
Preliminary Overheads
Preliminary overheads are among the most contentious elements of any variation claim. They fall into three broad categories:
- Fixed preliminaries comprise site establishment and mobilisation costs.
- Quantum-related preliminaries comprise costs tied to the volume of work.
- Time-related preliminaries comprise running costs that accrue with the duration of the project.
Hudson’s Building and Engineering Contracts
In 2012, the Technology and Construction Court (England and Wales) held that a contractor is entitled to recover prolongation costs, including site overheads, where employer-instructed variations cause delay. The practical point for employers and ERs is that preliminary items should be adequately broken down at the tender stage and supported by contemporaneous records. Employers should scrutinise any claim for additional preliminaries by reference to the relevant category, the causal effect of the compensation event, and the available records.
RIAI Comparative Reference
A brief comparison with the RIAI contract forms is instructive. Under Clause 13 of the RIAI 2017 form (Clause 6.4 of the RIAI 2025 form), variations are instructed by the Architect and are to be “fairly valued,” with day rates as a fallback. Where an omission is substantial, the contractor is entitled to reasonable compensation (Clause 14 of the RIAI 2017 form / Clause 6.5 of the RIAI 2025 form). Where measured work is reduced, the contractor is entitled to 10% of the value of the reduction. In practice, Clauses 14 and 6.5 are often heavily amended in the employer’s favour. The comparison is useful for employers and ERs who work across both the PWC and RIAI regimes, as the valuation philosophies differ in important respects, and the effect of any amendments should be carefully checked.
Key Takeaways
Variation power is not unlimited. The principles established in 1953 by the High Court of Australia, in 1987 by the English Court of Appeal, and in 1978 by the Supreme Court of Victoria define the outer boundaries. Employers should scrutinise whether an instruction remains within the contractual variation power before treating the resulting work as a Clause 10.6 adjustment.
Conditions precedent must be strictly observed. As the Technology and Construction Court (England and Wales) held in 2007, failure to comply with notice requirements can operate as an absolute bar to claims. The claims procedure is the gateway to valuation. Employers should check that notices, instructions and supporting information satisfy the contractual requirements before assessing the substance or value of a claim.
The Clause 10.6 hierarchy is mandatory. The Court of Appeal (England and Wales) confirmed in 2005 that the ERs must apply the valuation rules in sequence and cannot bypass higher-tier rules in favour of a discretionary fair valuation. Employers should ensure that the valuation record demonstrates the sequential application of each tier before any fair valuation is considered.
Fair valuation and quantum meruit are available as residual remedies. The relevant principles were established by the Court of Appeal (England and Wales) in 1990 and the Supreme Court (United Kingdom) in 2013, but these remedies arise only where the contractual mechanism has broken down. Employers should treat them as fallback mechanisms, not substitutes for applying the contractual hierarchy.
Preliminary overheads are the most contentious element. The Technology and Construction Court (England and Wales) confirmed in 2012 that prolongation costs, including site overheads, may be recoverable in principle, but an adequate breakdown at the tender stage is essential to a successful claim. Employers should require sufficient tender breakdown and contemporaneous records to allow any later claim to be tested.
The Capital Works Management Framework and GCC guidance inform PWC interpretation. Employers and ERs should be familiar with the broader framework within which the PWC operates, including relevant guidance notes and circulars, as these inform the ERs’ approach to valuation and the standards against which claims are assessed.
This two-part series has examined the complete lifecycle of a variation claim under the PWC, from the conceptual framework and conditions precedent through to the mandatory valuation hierarchy, cost-based valuation, and residual remedies. The overarching message for employers and ERs is one of procedural discipline: the substantive merits of a claim are irrelevant if the gateway requirements are not met, and the valuation hierarchy must be respected in the sequence in which it is set out. Fair valuation and quantum meruit remain residual remedies where the contractual valuation mechanism has broken down. Employers should ensure that their contract administration processes preserve that discipline from instruction through to valuation.
