Materials went up
after you quoted.

A quotation is an offer; once accepted, that price is the contract price and a later rise in your costs does not change it. What protects you is what you wrote before it was accepted: a validity period, a fluctuation provision, a provisional sum, or a stated exclusion. After acceptance your options are commercial rather than contractual.

The average is the wrong number to worry about

Materials inflation is usually discussed as one figure, and that figure is close to useless to a contractor.

On the Department for Business and Trade's provisional figures, construction materials prices for All Work rose 5.4% in the twelve months to May 2026. Underneath that: fabricated structural steel was up 13.1%, gravel, sand, clays and kaolin up 12.2%, and cement down 5.0% over the same period.

So in one twelve month window a steel-framed job and a concrete job faced opposite conditions. A firm reading "materials up five per cent" and adding five per cent to its allowances would have been badly wrong in both directions.

You are not exposed to a basket of materials. You are exposed to the two or three things your job is actually made of.

Which suggests the practical discipline: know which materials dominate your work, watch those specifically, and treat the headline index as background rather than as an input.

What protects a price, before it is accepted

Everything useful happens here. Four mechanisms, in ascending order of how much certainty they give away.

1. A validity period. The simplest and the most neglected. "This quotation is valid for 30 days from the date above." A quotation with no stated expiry is an offer that stays open indefinitely, which on a rising market is a real exposure, and it costs one line to close.
2. Back-to-back supplier quotes. Match your validity period to the validity of the supplier quotes behind it. Where your quote is open for 30 days and your merchant's is open for 7, you have taken 23 days of price risk without being paid for it.
3. A fluctuation provision. A clause allowing the price to be adjusted for changes in the cost of stated materials. Standard on longer contracts, negotiable on shorter ones, and worth asking for on anything where the programme is long enough for prices to move.
4. A provisional sum or a stated exclusion. Where one item is genuinely volatile, price it separately and say so, rather than burying a contingency in the rates where the client cannot see it and you cannot justify it later.

If you index a fluctuation clause, read this first

Worth its own section because it is a trap that looks like sophistication.

The obvious way to write a fluctuation clause is to link it to a published index. But DBT, which publishes the materials statistics quoted above, advises that its index values should not be relied upon for long-term contractual purposes, because they are based on relatively few quotes.

That does not make indexed clauses useless, and formal fluctuation formulae used on major contracts are a different and more robust animal. It does mean that casually writing "adjusted in line with the DBT index" into a subcontract is weaker than it looks, and that a clause tied to the actual invoiced cost of stated materials, evidenced by supplier invoices, is usually the more defensible construction on the kind of job this site is written for.

After acceptance, the options are commercial

If a fixed price has been accepted and your costs then rise, the honest position is that the contract price is the contract price. Being able to say what you can actually do is more useful than pretending otherwise.

• Absorb it. Sometimes correct, particularly where the sum is small relative to the relationship and the job is otherwise healthy.
• Ask, early and with evidence. Not a demand, and not at the final account. A conversation at the point you discover it, with the supplier invoice attached, has a materially better hit rate than the same conversation four months later. Clients dislike surprises far more than they dislike bad news.
• Look for the variation you have already done. On many jobs where materials have moved, the scope has moved too, and unclaimed variations are frequently larger than the materials gap. That is covered in getting paid for variations.
• Buy earlier next time. Where a material is volatile and storable, ordering on acceptance rather than on need converts a price risk into a cash flow and storage question, which is at least a question you control.

What does not work is silently substituting a cheaper specification. It is a defect claim waiting to happen and it damages the relationship far beyond the sum involved.

Whether you are on a quote or an estimate matters here

If what you sent was genuinely an estimate rather than a fixed quotation, and it said so and explained what could move the figure, the position on a later rise is considerably better. If it was headed Estimate but stated one firm figure for a defined scope with no qualification, that heading may not protect you.

The distinction turns on the substance of the document rather than the word at the top, and it is set out in quote or estimate, and which one binds you.

Where to start, on Monday

Open your quotation template and check for one line: a validity period. If it is not there, add it. That is the single highest-return change on this page and it takes a minute.

Then write down the three materials that dominate your work by value, and find out what each has actually done over the last year rather than what materials in general have done. For most firms one of the three has moved a great deal more than the headline, and that is the one worth a clause.