Self-Manage vs. Main Contractor Cost Comparison

Sometimes, yes. Usually not by as much as people expect, and sometimes not at all. The saving looks obvious on paper. Skip the 15-20% management markup and pocket it. But I've watched homeowners spend every evening and weekend for three months chasing plasterers, waiting at home for deliveries, and re-ordering tiles that arrived in the wrong shade. That time has a cost. The tool defaults to £30 per hour but if you're a solicitor or senior manager your time is worth two or three times that. Add the 10% risk premium for the rework, delays, and gaps that a contractor would have caught before they became problems, and the gap closes fast. On a £50,000 job the self-manage 'saving' often lands at £2,000-£5,000 after honest accounting.

They run the job so you don't have to. That means organising every trade in the right sequence. You can't tile before the plumber's roughed in, you can't board before the electrician's first fix. It means sourcing materials, managing deliveries, being on site every day to answer questions and make decisions in real time. It means carrying the risk when a roofer doesn't turn up and finding a replacement at short notice. I've had electricians miss circuits and plumbers forget to pressure-test, and both were caught before the walls went back on. The markup also covers a programme, a single point of contact, and a warranty on the work. For a project over six weeks and two or more trades, it's usually worth paying.

Three situations. First, if the project involves more than two trades working concurrently. The sequencing gets complicated and mistakes are expensive to unpick. Second, if you're not based in London or can't check in on the job regularly. Trades slow down or cut corners when no one's watching, and a contractor's reputation is on the line in a way yours isn't. Third, if the project involves structural work (steels, load-bearing walls, new foundations). Getting that wrong means Building Control won't sign off and you're looking at a re-do. We take on self-manage projects that have gone wrong two or three times a year. It's not the right outcome for anyone.