Certification - Scottish Construction Contracts - page 172

Accordingly, interim certificates are not normally stipulated to be conclusive in
respect of either the amount to be paid to the contractor or to the extent that they
provide that the works and materials are of satisfactory quality. In relation to the
last point, see Clark Contracts Ltd v. The Burrell Co. (Construction Management) Ltd
(2002). Interim certificates simply have provisional validity, see Beaufort Develop-
ments (NI) Ltd v. Gilbert-Ash NI Ltd and Another (1998). The amount certified in an
interimcertiicatecanusuallybechallengedduringthecurrencyoftheworks.he
procedure for challenging interim certificates is considered in more detail below.
In any event, the effect of interim certificates may be superseded by subsequent
developments and subsequent interim certificates. In relation to the valuation of the
work carried out, this can normally be revised at the time of issue of the next interim
certificate, see Scottish Equitable plc v. Miller Construction Ltd (2001). Most standard
formsofbuildingcontractallowforarevaluationofallworkcarriedoutintermsof
the contract at the date of issue of an interim certificate and not simply a valuation
of the work carried out since the issue of the previous certificate, see, for example,
clause 4.16 of the SBC. Confirmation that each interim certificate is intended to be
based on a revaluation of all work carried out can be found in William Verry Ltd v.
NorthWestLondonCommunalMikvah (2004). In this case the court indicated that
eachmonththeworkshavetoberevaluedsoastoensurethatthetotalvalueofwork
properly executed is ascertained. In addition, if work previously valued is discovered
to be defective, then there will have to be a downward adjustment of the gross value
previously certiied. he NEC3 puts the position beyond doubt by providing expressly
in clause 50.5 that the Project Manager corrects any wrongly assessed amount due in a
later payment certificate and this was confirmed in the case of RBG Ltd v .SGLCarbon
Fibers Ltd (2010) and SGLCarbonFibresLtd v. RBG Ltd (2012).
The fact that each interim certificate supersedes its predecessor has important
implications with regard to the prescription of claims. It was held in Scottish Equi-
table plc v. Miller Construction Ltd (2001) that the whole structure of the contract in
question allowed challenges to be made against certificates, notwithstanding the fact
thatachallengeonthesamebasiscouldhavebeenmadeagainstanearliercertiicate.
In short, it appears that a failure to challenge one interim certificate in respect of a
particular issue does not automatically trigger the start of the prescriptive period in
respect of that issue as it also falls to be valued in subsequent interim certificates.
Support for such a position is also to be found in the English case of Henry Boot
Construction Ltd v. Alstom Combined Cycles Ltd (2005).
With regard to the quality of work and materials, the issue of an interim certificate
does not normally prevent the issue of instructions or directions in relation to reme-
dying defective or unsatisfactory work. Indeed many defects may not be apparent at
the time of issue of an interim certificate. Clause 1.10 of the SBC specifically provides
that a certificate is not conclusive evidence that any work, materials or goods to which
it relates are in accordance with the contract. Similarly, clause 3.6 of the SBC stipulates
that the Contractor remains wholly responsible for carrying out the Works in accor-
dancewiththecontractnotwithstandingthefactthatthevalueofthatworkhasbeen
included in a certificate for payment.
In many standard forms of building contract, the issue of an interim certificate is a
condition precedent to payment of interim amounts to the contractor. In such cases if