How to price a job when you can't see the full scope yet

How to price a job when you can't see the full scope yet

When you can't see the full scope, price what you can verify at a firm rate, flag the uncertain parts as provisional sums or a day-rate allowance, and put a clear condition in the quote stating what would trigger a revised price. This protects your margin without forcing you to guess a number you can't stand behind - and it keeps the client informed instead of surprised.

Every trade runs into this: a rotten joist you can't see until the floorboards are up, a drain run that might be root-damaged, wiring behind a wall that was "definitely rewired in the 90s" according to the homeowner. You can't open every wall before quoting. But you also can't just write one lump number and hope the hidden bit doesn't bite you. The fix isn't a better guess - it's a better structure for the quote itself.

Separate the known from the unknown - on paper, not just in your head

Most pricing disputes happen because the quote reads as one single price, even though mentally you'd already split it into "stuff I'm sure about" and "stuff I'm not." The client only sees the one number. So the first step is to make that split visible in the document itself.

Structure the quote in two clear blocks:

• Fixed-price items - anything you've measured, seen, or can reasonably predict from experience. These get a firm price, no caveats.
• Provisional items - anything hidden, inaccessible, or dependent on what's found once work starts. These get an estimated allowance, clearly labelled as provisional, with the condition that triggers a change.

A roofer quoting a re-roof might fix the price for tiles, felt and labour, but mark timber replacement as provisional: "an allowance of up to 10 rafters is included; additional rotten timber found once the roof is stripped will be charged at €X per rafter, agreed before work proceeds." That's not hedging - that's precision about what you actually know.

Use a day-rate or unit-rate fallback for the grey areas

For the parts you genuinely can't scope, the cleanest tool isn't a bigger contingency buffer - it's a pre-agreed rate. Instead of guessing "probably €800 for extra groundwork," quote a day rate or a per-metre/per-unit rate that only gets invoked if the hidden condition turns up.

This works because it moves the risk conversation from "trust me, it'll be about this much" to "here's exactly what it costs if X happens, agreed in advance." Clients generally accept this far more readily than an open-ended "we'll see" clause, because the number is already fixed - only the quantity is unknown.

Typical examples:

• Plumbers: a fixed day rate for additional pipework if old copper is found to be corroded.
• Electricians: a per-point rate for extra sockets or circuits uncovered once a wall is opened.
• Groundworkers: a per-tonne rate for unexpected rock or contaminated spoil removal.

Write the rate into the quote itself, not as a verbal aside on site. If it's only said out loud, it's not enforceable and the client has no reason to remember agreeing to it.

Do a short paid survey when the stakes are high enough

If the uncertainty is large enough that a wrong guess could sink your margin on the whole job - a full rewire, a structural extension, a drainage job with no access history - it's often worth charging a small fixed fee for a proper site survey before the full quote goes out. This isn't the same as a free visit; it's a paid diagnostic step that produces a firmer quote afterwards.

Framed correctly, clients tend to see this as reassurance rather than friction: you're not guessing at their expense, you're finding out before committing either of you to a number that might not hold. Many contractors credit the survey fee against the job if it goes ahead, which removes most of the objection.

This is also where AI tools for scoping a job earn their keep - comparing a site photo set or a quick scan against typical material and labour patterns can tighten your provisional allowance before you even write the quote, so your "unknown" portion is smaller and more defensible. If you want a wider look at how quoting software handles this kind of risk, our piece on whether AI quoting software is worth it covers where it genuinely helps and where it doesn't.

Write the variation trigger in plain language

The single biggest cause of disputes isn't the provisional sum itself - it's that the client didn't register it as a real condition. "Subject to survey" buried in small print doesn't count. Spell out, in the body of the quote, exactly what would cause the price to change and what happens next:

"If, once the old plaster is removed, the wall is found to require additional lathing beyond the 4m² allowed for, we will notify you in writing with a revised price before continuing. No additional work will be charged without your agreement."

That one paragraph does three things: it tells the client what to expect, it protects you from being accused of padding the invoice later, and it gives you a clean pause point if the number changes significantly. For a wider look at getting the base numbers right before you even reach the provisional parts, see our guide on how to quote a construction job without underpricing it.

Don't let "we'll sort it on site" become your default

It's tempting, especially on smaller jobs, to just quote a round number and handle surprises verbally once you're in. It's faster to write and it avoids an awkward conversation up front. But it's the single most common reason small firms end up working for free on the unknown bit - because there's no document to point back to, and the client remembers a fixed price, not a flexible one.

The provisional-sum approach takes five extra minutes to write. It's cheap insurance against a conversation that otherwise happens after the work is already done, when you have far less leverage.

Frequently asked questions

What's the difference between a provisional sum and a contingency?

A provisional sum is an allowance for a specific, named item that might change (e.g. "up to 10 rafters"), tied to a condition. A contingency is a general buffer added to the whole price to cover unspecified risk - it's less transparent and harder for clients to accept, since they can't see what it's actually for.

Should I just quote high to cover the risk instead of using provisional sums?

Quoting high to cover unknowns usually costs you the job on price comparison, and if the risk doesn't materialise, you've simply overcharged a client who may notice. A clearly labelled provisional sum keeps your base price competitive while still protecting your margin if the risk is real.

Can I charge for a site survey before giving a quote?

Yes, and it's common practice for higher-risk or higher-value jobs. Many contractors charge a small fixed fee and credit it against the final job if it goes ahead, which reduces client resistance to the fee.

What happens if I find a problem but didn't mention it as provisional in the quote?

Legally and reputationally, this is weak ground - without a written condition, the client can reasonably argue the original price should stand. This is exactly why naming the specific uncertain items up front matters more than a vague disclaimer.

Does AI help with scoping unknown site conditions?

AI tools can speed up pattern-matching from photos, past jobs and typical material quantities, which narrows down how big your provisional allowance needs to be. It won't replace a physical inspection where the risk is high, but it reduces the guesswork on routine jobs.

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If you're quoting jobs with uncertain scope every week, a structured quoting tool makes it far easier to separate fixed items from provisional ones consistently, instead of rebuilding the logic from scratch each time. Visit Håndværker AI to see how our AI quoting tools can help you handle this on every job, not just the easy ones.

This article was written with AI assistance and checked for accuracy by Carl & Martin before publishing.