Interim Valuations: How to Measure and Value Work in Progress

Every month on a live job, you have to answer one deceptively hard question: how much work have I actually done? Not roughly. Not "we're about halfway." A number, in pounds, that you can stand behind — because that number is what you apply for, and getting it wrong costs you either way.

Under-measure and you've done work you're not being paid for yet — you're financing the client's project with your own cash flow, which for a small contractor is exactly the squeeze that kills firms. Over-measure and you've been paid for work you haven't done, which gets corrected at the next valuation or, worse, unravels at the final account when the money's already spent. Accurate interim valuation is how you stay on the right side of both.

What an interim valuation is

An interim valuation is the assessment of the value of work properly done up to a certain date, so it can be included in an application for payment. It's a snapshot: at this point in the job, this much has been earned. Do it monthly (the usual cycle), and each valuation captures the additional work since the last one.

It sounds simple. The difficulty is that "work properly done" has to be measured and valued accurately across everything on the job — the measured works, the variations, the materials, the preliminaries — and each of those has its own rules. Get the method right and it's a repeatable monthly discipline. Get it wrong and you're either leaking cash or building up a correction you'll have to repay.

What goes into the number

A complete interim valuation pulls together several components. Miss one and you've undervalued.

Measured work. The core: the value of the contracted work completed to date, assessed against the contract rates or the priced schedule. If an element is priced at £65/m² and you've completed 350 of 500m², that element is worth £22,750. Measure what's actually done, honestly — not what you hoped to finish, not what's nearly there.

Variations. Agreed variations at their agreed value. Instructed-but-not-yet-agreed variations at a realistic assessment of your entitlement — being honest here matters, because overvaluing pending variations inflates the application and creates a correction later. Include what you can properly justify, not what you're hoping for.

Materials on site. Most contracts let you claim for materials delivered to site but not yet built in, subject to conditions (properly stored, protected, sometimes evidence of ownership). This is legitimate value — the money's gone out of your account to the merchant, so claim it — but know your contract's rules on it.

Materials off site. Sometimes claimable too (fabricated steelwork, made-to-order items held at the supplier's), but usually only under stricter conditions — vesting certificates, insurance, clear identification. Check before you assume.

Preliminaries. Your time-related and fixed prelims, valued for the period. These are real costs you're incurring monthly — site management, welfare, plant, scaffolding — and they need to be in the valuation, apportioned sensibly against progress.

Retention. Then the retention gets deducted — typically 5% — so your gross valuation and your net payable are different numbers. Know both.

How to measure honestly and defensibly

The word "properly" in "work properly done" is doing a lot of work. Two contractors can look at the same job and produce different numbers, and the difference between a valuation that gets certified without argument and one that gets cut is usually rigour.

• Measure against the priced document. Your valuation should mirror the structure of your pricing schedule or bill, element by element, so it's transparent and checkable. A number that can't be traced back to the priced work is a number the QS will challenge.
• Assess genuine percentage complete. For an element part-done, what's the honest proportion? Not "feels like 70%" — a considered assessment you could justify walking the job. The temptation to round up compounds across a valuation into a figure you can't defend.
• Keep the evidence. Measurements, photos, records of what was complete at the valuation date. If the assessment is questioned, contemporaneous evidence settles it.
• Don't double-count. Work covered by a variation shouldn't also sit in the measured works; materials claimed as on-site become measured work once installed. Sloppy accounting here creates errors in both directions.

The aim is a valuation the certifier can follow and agree without a fight — accurate enough that it's paid in full, transparent enough that it's trusted, and evidenced enough that it holds if it's questioned.

The two failure modes

Under-measuring is the quiet killer. Busy contractors, short on time, throw together a conservative application to avoid an argument — and systematically fund the client's job with their own money, month after month. Every pound of work done and not applied for is a pound of your cash tied up in someone else's building. Over a big job, that adds up to serious money and real cash-flow pain. Measure everything you've genuinely earned. It's not aggressive to claim what you're owed — it's basic commercial hygiene.

Over-measuring is the slower-acting poison. Overstate progress and you get paid ahead of the work — which feels fine until the next valuation corrects it, or the final account exposes it, and now you owe money back on a job where the cash has already gone. Persistent over-measuring also destroys your credibility with the certifier, so your honest valuations start getting cut too. The discipline is simple: claim everything you've done, and nothing you haven't.

Making it practical

At Construction AI, the interim valuation builds from the priced schedule and the live project data — measured work against rates, agreed and pending variations, materials, prelims and retention pulled together into the application rather than reassembled by hand each month. Because it mirrors the priced document element by element, the valuation is transparent and traceable — the certifier can follow it, which is exactly what gets it paid in full and on time. And because it feeds straight into the CVR, your value position and your margin position stay in step.

Valuing work in progress is a monthly test you can't skip and can't fudge. Measure everything you've genuinely earned, value each component by its own rules, keep the evidence, and make it traceable to the priced work. Do that and you claim what you're owed, keep your cash where it belongs — in your account, not the client's project — and never get caught out at the final account.

Frequently asked questions

What is an interim valuation in construction?

An interim valuation is the assessment of the value of work properly done up to a certain date, so it can be included in an application for payment. It's usually done monthly, with each valuation capturing the additional work completed since the last.

What's included in an interim valuation?

Measured work completed to date (against contract rates), agreed and realistically assessed pending variations, materials on site (and sometimes off site) subject to contract conditions, preliminaries for the period, less retention.

How do you measure work in progress accurately?

Measure against the priced document element by element, assess a genuine percentage complete you could justify on site, keep contemporaneous evidence (measurements and photos), and avoid double-counting between measured work, variations, and materials.

What happens if you under-measure an interim valuation?

You've done work you're not yet being paid for, effectively financing the client's project from your own cash flow — a serious squeeze for small contractors. You should claim everything you've genuinely earned.

What happens if you over-measure?

You get paid ahead of the work done, which is corrected at the next valuation or exposed at the final account when the cash has already been spent. Persistent over-measuring also damages your credibility with the certifier.