You price the job, then the start date slips. Three months later you're finally mobilising, and the rates you priced against aren't the rates you're now paying for materials or labour. The number you bid with is no longer the number the job actually costs, and there's no one to send that difference to except yourself.
So how long a construction quote stays valid isn't really a question about paperwork. It's a question about how fast the market under your price is moving, and whether you've done anything to protect yourself if it moves before you buy.
A price has a shelf life
A rate for concrete, steel, or a subcontractor package is only good for as long as the market stays roughly where it was when you priced it. The longer the gap between pricing the job and actually buying the materials and booking the labour, the more chance that gap has cost you money you never accounted for.
Here's a hypothetical to show how quickly it adds up. Say materials make up half the value of a job, and by the time you start, the materials you priced have gone up 6% on average. That's 3% on the whole job. If your margin was thin to begin with, a good slice of it has gone before anyone's picked up a trowel, and none of it was anything you did wrong on site.
Labour does the same thing, just less visibly. A gang that was available at one rate in spring may be booked elsewhere by summer, and the replacement costs more. Subcontractors re-price when their own costs move. If their quote was given against your old tender date, it may not hold either.
How long a construction quote stays valid in a moving market
There's no single answer, and anyone who gives you a fixed number for every job is guessing. It depends on what's in the job and how volatile those items are when you price it. A job heavy in materials that are moving a lot has a shorter safe shelf life than one that's mostly labour on a settled rate.
What you can control is whether the tender says how long the price holds. A tender with no validity period is, in practice, an open offer. The client can accept it whenever suits them and expect you to hold the figure. A stated validity period, and a clear line on what happens after it expires, puts the risk back where it belongs.
A useful way to decide the period is to look at the job's biggest cost items and ask how confident you'd be holding each of them. If your merchant will only hold a price for a short time, your tender can't sensibly hold for longer on those items. If most of the value is in labour you've got booked, you can afford to be more generous. The answer to how long a construction quote stays valid comes from the inside of your price, not from a standard sentence you paste into every tender.
Clients rarely object to a stated period. They object to a price that changes without warning.
Protecting a tender when the start date is uncertain
You can't stop a start date slipping. You can stop it being your problem alone.
- State a validity period. Put it in writing on the tender. After that date the price is open to review.
- State the assumed start date. If the price is based on starting in a particular month, say so. A late start is then a visible change, not an argument.
- Check the contract's fluctuation position. Some JCT forms offer fluctuation options that allow certain cost changes to be recovered. If the contract you're signing is fixed price with those options switched off, you're carrying all the movement.
- Get sub quotes with a matching validity. There's no point holding your price for three months if your groundworker's quote runs out after one.
- Re-price before you sign. If the gap between tender and contract has been long, check the big rates again before you commit.
A tender is only as good as its shelf life. If you don't say how long the price holds, you've agreed to hold it for as long as the client likes.
Price close to when you'll actually build
The way to protect a tender from all this is to price it as close as you reasonably can to when the job will actually start, using rates that reflect the market at that point, not the market from whenever the enquiry first landed. If there's a long gap between bid and start, that's worth flagging and pricing for, rather than hoping it comes out in the wash.
We price every job against current UK rates at the point we measure it, so the number in your bill of quantities reflects what things cost now, not a stale figure from months back. Because the quantities and rates sit separately in the bill, it's also quick to re-price when the start date moves. The measured quantities stay the same. Only the rates need checking again.
That's the part people underestimate. A lump sum is hard to update, so it tends not to get updated. A measured bill can be re-rated line by line in a fraction of the time it took to build. For more on why stale rates cause so much damage, see pricing on last year's rates.
A quick rule for any quote that's been sitting
If a client comes back to accept a price you gave some time ago, ask yourself one thing before you say yes: would I price this job the same way today? If the honest answer is no, the quote has already expired, whatever the letter says. Re-check the biggest rates and have the conversation now, before you've mobilised and found the rates have moved on you.