Scope creep on engineering projects rarely arrives as one big change. It comes as a string of small, reasonable requests: one more drawing revision, an extra site meeting, a quick look at an alternative layout. Each one feels too small to price. Together they can take a third or more of the profit out of a fixed-fee job, and nobody notices until the job closes. This guide shows how to put a £ figure on it, why it happens, and how to stop it without falling out with your clients.

What scope creep looks like in practice

In engineering and technical consultancies, the extra work usually falls into a few familiar groups:

• Extra revision rounds after the client changes its mind or its architect does.
• Additional meetings, calls or site visits that weren’t in the fee.
• Design for options the client “just wants to see” before choosing.
• Late information from the client or other consultants that forces rework.
• Small additions: one more calculation, one more report section, one more drawing.

None of these is unreasonable for a client to ask for. The problem is doing them inside a fee that was priced for something smaller.

What scope creep on engineering projects costs: a worked example

Take a made-up building services design consultancy, Example MEP Design Ltd. It quotes a fixed fee of £18,000 for a design package, estimated at 200 hours. Its cost per hour (salary, employer costs and a share of overheads) is £60.

• Planned cost: 200 hours × £60 = £12,000.
• Planned margin: £18,000 − £12,000 = £6,000, or 33.3%.

During the job the client asks for an extra revision round (16 hours), three more design team meetings (3 × 4 = 12 hours) and a redesign for a changed plant room layout (22 hours). That’s 50 extra hours, all done inside the original fee.

• Actual cost: 250 hours × £60 = £15,000.
• Actual margin: £18,000 − £15,000 = £3,000, or 16.7%.
• Effective rate: £18,000 ÷ 250 hours = £72 an hour, against £90 an hour planned (£18,000 ÷ 200).

Half the planned profit has gone. If those 50 hours had been billed as variations at the firm’s £90 charge-out rate, the extra fee would have been 50 × £90 = £4,500, and the margin £7,500 instead of £3,000.

Now scale it. If the firm runs 40 fixed-fee jobs a year and half of them carry £2,000 of unbilled extra work, that’s 20 × £2,000 = £40,000 of profit a year, with no single job looking like a disaster.

Why it happens

The scope was never written down tightly enough

If the quote says “MEP design to RIBA Stage 4” and nothing else, almost any request can be argued to be in scope. The fee assumed a number of revisions and meetings, but the client never saw that assumption.

There’s no simple way to say “that’s extra”

If raising a variation means a formal letter and a new quote, engineers skip it for anything under a day’s work. Most scope creep is made of exactly those small pieces.

The person saying yes isn’t the person who prices

Project engineers want to help the client and keep the job moving. They’re rarely asked to think about the fee, and nobody has told them what to say instead of “no problem”.

Extra time is booked to the job, not flagged

When the extra hours go into the same job code as everything else, they disappear into “the job ran over”. By the time anyone checks, the work is done and asking for more money feels like an afterthought. We covered how to spot this in our guide to checking job margins.

How to control scope creep without upsetting clients

1. Write the scope with assumptions and exclusions. State what the fee includes: the number of revision rounds, meetings and site visits, and what information you expect from the client and by when. List what’s excluded. Clients rarely object to this, because it tells them what they’re buying.
2. Put a variation rate on every quote. A line such as “Additional work outside this scope is charged at £90 an hour, or quoted separately, and agreed before we start” removes the awkward conversation later. Our guide to fixed fee vs time and materials covers how to combine a fixed fee with a variation rate.
3. Use a one-line change note before doing the work. Email the client: what they’ve asked for, the estimated hours or fee, and “please reply to confirm”. It takes two minutes and gives you a written record.
4. Give variations their own time code. Staff book extra work to a separate code so it shows up as a variation, not as an overrun. Project tools such as Xero Projects and QuickBooks Online Projects, and most practice software, let you track time against separate tasks.
5. Bill variations with the next stage invoice, not at the end. Agreed extras added to the next stage payment get paid while the client still remembers asking for them.
6. Tell your team what to say. Replace “no problem” with “Happy to do that. It’s outside the current scope, so I’ll send you a quick note with the cost before we start.”

Have a solicitor check any scope, variation or payment wording before it goes into your standard terms or contracts. This guide covers process, not legal advice.

When it’s fine to absorb a change

Sometimes doing a small extra for free is the right call: a good long-term client, a ten-minute fix, or a change caused by your own mistake. The difference is doing it on purpose. Record it on the change log and show it on the invoice as “Additional revision: no charge”. The client sees the goodwill, and you can see what it cost.

What to do this week

1. Pick your last five fixed-fee jobs and compare quoted hours with actual hours.
2. For each overrun, list how much was client-requested extra work and how much was your own estimate being wrong. They need different fixes.
3. Multiply the client-requested hours by your charge-out rate. That’s what scope creep cost you on those five jobs.
4. Add an assumptions, exclusions and variation rate section to your quote template.
5. Set up a variation time code and a one-line change note email your engineers can copy.

If the five-job figure is large, it’s usually worth also checking how your fees and charge-out rates are set, which is part of what we look at in our profit and cash review. You can see our packages on the services page.

Find out what your leaks add up to

Our free leak calculator takes a few numbers and gives a rough £ figure for cash held by late payers and slow invoicing, plus your likely price gap. It takes about two minutes. If you’d like to talk through where your business is losing money, book a free 30-minute call.