Project Manager, Architect or Main Contractor: Who Do You Actually Need?

Most homeowners planning an extension or loft conversion have heard of all three roles and aren't quite sure where one stops and the next starts. That confusion costs people money — either because they've paid for overlapping services, or because they've assumed someone was covering something nobody actually was.

The architect

Designs the project: drawings, planning applications, building regulations submissions, and — if appointed for it — contract administration during the build. An architect's job is to solve the design and regulatory problem: what can be built, how, and getting it approved.

What an architect typically isn't doing: scrutinising your builder's pricing line by line, chasing day-to-day site decisions, or protecting your budget against creep once work starts. Some offer contract administration as an add-on, but it's priced and scoped separately, and it isn't the same as someone watching your money specifically.

The main contractor

Builds the project. A good main contractor manages their own trades, their own programme and their own margin — which is exactly the point: their commercial interest is in their own profitability, not in minimising your spend. That's not a criticism of builders; it's just the structure of the relationship, and it's why it's worth having someone on the other side of the table who isn't.

The client-side project manager

Works for you, specifically, with no commercial relationship to the builder. In practice that means reviewing quotes and scope before you sign anything, sourcing materials at trade rather than retail prices, sitting in on site decisions so you're not the one arbitrating disputes, and tracking variations before they balloon — generally being the person asking "why has this gone up?" on your behalf rather than the builder's.

So who do you actually need?

For anything beyond a straightforward like-for-like refit, most homeowners end up needing an architect and a main contractor regardless. The genuinely optional role is the third one — and the honest answer depends on how much time you have, how comfortable you are scrutinising construction quotes, and how much is riding on the budget. If you are weighing that option, how much a client-side project manager costs sets out the usual fee models without inventing a single number for your job.

Skip a project manager if you have real construction experience yourself, genuinely have the time to be on-site regularly, and are comfortable reading a builder's quote line by line. Get one if this is a six-figure project, you have a demanding job, you've never managed a build before, or the last time you compared two builder quotes you weren't sure what the difference actually meant.

Plenty of people manage their own renovations successfully, and we're not precious about that. But the ones who call after things have already gone wrong almost always say the same thing: they didn't know what they didn't know, and nobody was checking on their behalf until it was too late.

Still unsure which combination you need? Tell me about the project — or read how client-side fees work and what the service covers first. Happy to say if an architect and a good builder are enough on their own.