Guide

Do you need a
project manager?

What a project manager actually does on a house build, what it costs, how it differs from the other routes — and an honest answer about when you're better off without one.

By Phil Baily · Founder, Elizabeth Homes

In this guide

What a project manager actually does

It's one of the most misused titles in building. Your builder will tell you they project manage. Your architect may say the same. Both are partly true — and that's exactly why people get confused about whether they need someone else.

A project manager, properly speaking, runs the process rather than the trowel, and works for you. They price and tender the specification so every builder is quoting the same thing. They agree a realistic programme, then hold it. They check valuations before you pay them, scrutinise variations before they become your problem, chase the design team for the information the site needs, and see the job through snagging and handover. The builder builds; the project manager makes sure what's built is what you agreed, at the price you agreed.

Do you actually need one?

Here's the honest answer that most people offering the service won't give you: often, no.

On a straightforward build with a competent contractor and an engaged architect, the management is usually covered between them — the architect administers the contract, the builder runs the site, and it works out. That's how most home projects are delivered, and there's nothing wrong with it.

A project manager earns their keep in three situations:

  • The job is big or complex enough that the risk is real. The more money and moving parts, the more a small percentage saved outweighs the fee.
  • You haven't the time. Managing a build properly is not an evenings-and-weekends job. If you're not available in working hours, decisions get made without you — and they cost.
  • You can't tell a fair price from a bad one. This is the big one. Most people building a home have never priced construction work in their lives, and they're negotiating with someone who does it every day.

If none of those apply to you, save your money. We'd tell you so.

What it costs

Professional project management on private residential work is commonly quoted at around 5–8% of build cost. On a £1m build that's £50,000–£80,000, which sounds like a lot until you consider that a 5% error in a tender — or a run of unchallenged variations — costs the same and buys you nothing.

The percentage model has a flaw worth naming, though: it rewards the manager when the job gets more expensive. We'd rather scope a fee to what you actually need — from oversight at the key stages to full hands-on management — and agree it up front.

Where the money is really saved

Not on site. By the time the diggers arrive, most of your money is already committed. It's saved earlier, and quieter:

  • In the specification. A vague spec means every builder prices a different house and you can't compare them. A tight one means you're comparing like with like — and that alone moves the number.
  • In the tender. Knowing what the work should genuinely cost is the difference between negotiating and hoping.
  • In the variations. This is where budgets quietly run away. Every change should be tested on whether it's necessary, whether it's your fault or theirs, and whether it's fairly priced. Most aren't tested at all.

The blunt version: a project manager who only turns up once you're on site has missed the part where they'd have paid for themselves.

How it differs from the other routes

There are three ways to have a home built, and they differ by one thing: who carries the price risk.

  • Design & build — the builder carries it. You agree a fixed or capped price and hand it over. Most certainty, least involvement, and changes are expensive.
  • Construction management — you carry it. You hold the trade contracts directly and a construction manager procures and runs them for you, open-book. Savings are yours; so are overruns.
  • Project management — your builder carries it, on an agreed price, and a project manager acts for you to make sure that price and programme hold.

So project management isn't a rival to construction management — it's a different structure. Under CM your manager is doing the buying as well; under PM someone else has priced the risk and your manager's job is to hold them to it. Compare the three routes side by side.

Choosing one

Three questions worth asking anyone you're considering:

  • Have you built, or only advised? There's a world of difference between someone who has carried the risk of delivering buildings and someone who has watched other people do it.
  • Are you independent of my builder? If they're connected, they're marking their own homework.
  • How are you paid, and what happens if the job gets more expensive? You want the answer to that to be uncomfortable for them, not for you.

Frequently asked questions

What does a project manager actually do on a house build?

They run the process rather than the trowel: pricing and tendering the specification, agreeing a realistic programme, checking valuations, scrutinising variations, chasing the design team for information, and holding cost and quality to account through to handover. They work for you, not for the builder.

What does a project manager cost?

Professional project management on private residential work is often quoted at around 5–8% of build cost. Whether that's worth it depends entirely on the size of the job — on a large or complex build, a good PM should save more than they cost by testing prices and stopping variations running away. On a small, straightforward job, they may not.

Do I need a project manager if I have an architect?

Often not. On many builds the architect administers the contract and the main contractor manages the site between them, and that's perfectly adequate. A separate PM earns their money where the project is large or complex, where the value at risk is high, or where you simply haven't the time or experience to hold a builder to account.

Is a project manager the same as a construction manager?

No. A project manager oversees a build where a main contractor holds the trade contracts on an agreed price. A construction manager works on a route where you hold the trade contracts directly, and they procure and run those trades for you. Different structure, different risk.

Can I project manage my own build?

Plenty of people do, and some do it well. Be honest about three things: the time it takes (it is not an evenings-and-weekends job), whether you can tell a fair price from a bad one, and whether you're willing to have difficult conversations with people you see every day on site. If any of those is a no, it's worth paying someone.

When should I appoint one?

Before the build is priced, not after. Most of the value a project manager adds is in the specification, the tender and the contract — by the time work has started, the expensive decisions are already made.

Weighing it up? See how our project management service works, or start a conversation — we'll tell you honestly if you don't need us.