Do I really need a project manager for large extension?

[mum2015]

We are planning for a large extension but not sure if we need a project manager or not. We have two builders in mind to ask for quote and based on their availablity and quote would choose one of them. They both have some sort of workforce team for basic build and can get other tradesmen for jobs their guys cant do.
Do we still need seperate project manager? They seem to ask for quite some fees. What exactly project managers do if they arent actually related to the builder?

We didn't need one for our triple garage with accommodation above it. It is large - as big as your large extension I'll wager.

Do you know anyone who has recently had building work done? I would always go with a personal recommendation for builders. Too many of them are utterly crap.

We need to build a gym now and are going back to our trusted builder. We are having to wait 12 months for him to become available (but I am loathe to consider anyone else)

I think it depends how much project managing you want to do! Builders do need managing, all the time. A project manager would be separate from the builder so is there to protect your interests (i.e. not let them just do what they want) and should make sure the work is done to a good standard. They will be able to make sure the initial quote is as comprehensive and fixed as possible to make sure there are minimal changes during the build, and then if there are any changes they will be able to make sure you aren't screwed over by the builder on additional costs.

I'm a general practice surveyor (not a building one) and I've managed a few building projects but it is quite a difficult job without a lot of building knowledge, and take a lot of time too. If you have some basic building/budgeting knowledge, are a quick learner, organised and decisive and have lots of spare time I would say have a go yourself. Otherwise get a project manager! As you say, they cost a fair bit - make sure when you do your budget that you include plenty for professional costs (PM, structural engineer, building regs approval + many others) as they always end up being more than you think they should be!

"Builders do need managing, all the time"

Mine didn't

Although - our architect did visit the site a few times to see how it was progressing

You shouldn't need to.
A building company is a main contractor. As you say they have some employees but mainly contract in the different trades i.e. bricklayers, plasterers, electricians.
You can be your own project manager. In this instance you find your own tradespeople to do the work and manage the timings and deliveries etc. Or you employ and PM who brings in trades people.
The benefit of a building company is that they have a relationship with the different trades and can use loyalty to get them in to do the jobs in a better timeframe.
Perhaps if you have a very specific build in mind you may require another level of management. For instance if you were very remote from the build. Or perhaps if you were renovating a listed property, you may use a builder to do the extension and use further specialised trades in the house, and if you had a specialist roof system that was outside of the main contractors control. Ie if you are bringing in trades yourself you may need further help with managing those aspects of the build.
If its a (reasonably) straightforward extension, then no.

Our lovely builder designated a project manager from his team for every stage of our extension. We had a 24/7 mobile number throughout. He wasnt the cheapest firm but not the most expensive either. And he had insurance cover up to £1m. Building work is very stressful so make sure you know exactly what you are paying for and how much project management is included.

hmcAsWas. I need their number!

I guess if you set the whole thing up well, with comprehensive drawings, specification, tender documents etc and it's a reasonably straightforward new build then a good builder could run it without problems. The projects I did were refurbishments, one on a listed building, so there were always things being uncovered that needed decisions/changes, and I wouldn't have trusted the builder to make those decisions, even though they were pretty good.

Thank you. Looks like a good project manager would be worth the cost. But if I cant find a good one, I should set the whole thing up well, with comprehensive drawings, specification, tender documents etc and builder has team and knows other tradesmen then it would be manageable.

My builder would have hated having someone overlooking everything he did ! They arranged all the trades themselves and worked with people they could rely on and trust,

Get yourself a good builder you shouldnt need a project manager

I agree with badger. We've just had a large double storey extension and the builder (building firm) managed the build. He had his own builders / general labourer / joiner / electrician and arranged for others (plasterer / gas engineer / plumber) to come as they were required. At each stage, he gave me advance notice of "decisions" I.e. you'll need to make a final decision about which colour window frames you need by Wednesday / we need the toilets in 2 weeks / flooring in 3 weeks etc. He responded to emailed and calls within minutes. I was very organised and around so this helped.

So, depends on how good your builder is and how organised you are.