How to shortlist good builders

We are now approaching the point in the process that homeowners feel most anxious about: speaking to builders for quotes. Unfortunately, this anxiety is at least in part well placed because rogue traders exist and projects do go wrong. However, for every rogue, there is a skilled, experienced and trustworthy builder who would do an excellent job of building your extension. How do you sort the good from the bad? Well, you can start by triangulating a shortlist of good builders.

You want to receive three quality quotations for your extension. And because not all builders will follow through, shortlist five.

Don’t be tempted to overkill with a longer list – five is sufficient. In fact, done properly, shortlisting five will be an achievement in itself.

How to shortlist good builders - builders active on mobile phone

What is triangulation when it comes to shortlisting builders?

Triangulation is used in industry to increase the credibility and validity of data, and the more credible the data, the more trustworthy it is. The way to triangulate a shortlist of good builders for your project is to have them come recommended, accredited and with a fresh and relevant social feed. The more boxes you can tick, the more trustworthy the data.

Weed out potential rogue builders

Note: now is not the time to carry out full due diligence – that will come once you’ve had your quotes in. Right now, the focus needs to be on weeding out potential rogues by triple-filtering the candidates that make it onto your list. Essentially, the mission is to make sure their stories check out across different sources. You may wish to recall the builders you spoke to when you were initially deciding whether to extend. Providing they tick these three boxes, there is no reason they shouldn’t make it onto your shortlist.


There is no better place to start than by asking for a recommendation. It is very reassuring when someone you know has already used a builder and has a positive experience to share. A word-of-mouth referral from someone you know is the best, because making an introduction requires effort from the person referring. Otherwise, shout-outs via Facebook or neighbourhood apps like Nextdoor are also a fair place to start. Your architect is also a valuable source of recommendations, as they may have worked with builder with the right skill sets for your project type. And who better to recommend than the person in charge of designing the scheme?

The power of a referral lies in being connected by a third party, as it provides an extra, unspoken layer of accountability as well as a point of mutual recourse, should it later be required. A caveat of caution: marketing agencies have monetised the power of referrals by setting up ‘accreditation’ websites (more on this here), so it is vital to ensure the validity of any referrals you received. You can do this by ticking off the next two considerations.


You can expect to see a professional builder accredited by the appropriate industry bodies. If you run a search on builders’ accrediting bodies, the returned results will number into the tens of pages, and it’s impossible to tell the credible bodies from the marketing websites or the relevant bodies from the ones that cater for larger-scale contractors. For the home improvement and renovation sector, the two accrediting bodies of particular relevancy are the Federation of Master Builders (FMB) and Which? Trusted Traders.

Federation of Master Builders

The FMB, a non-profit industry body, established in 1914, is the foremost representative of the classic residential builder, i.e. the type you need for your extension. They are the voice of the industry, educating and keeping their members informed of latest developments, so you have the assurance that an FMB member will be pre-vetted to a level and well-informed. The FMB also offers dispute resolution for its members’ customers.

Which? Trusted Traders

The much-loved consumer body Which? has an accreditation scheme in place to protect consumers from rogues. Their Trusted Traders scheme gives homeowners real confidence that they are dealing with bona fide and well-established businesses. Becoming a Trusted Trader is a deliberately burdensome process, where Trading Standards are sent into inspect a prospective member’s place of work, years-old invoice records checked, past and present client and suppliers called upon to give references, and more. Builders who are accepted onto the scheme have earned their place on it. Which? also serves as a customer review repository.

If accredited with both the FMB and Which?, the chances are the builder will have a level of professionalism about them.

Social feeds

Check out the candidates across their social platforms. The digital sphere has grown beyond Facebook and Twitter, although these are still great for a nosey. Hit the builder you’re considering up on Instagram, Pinterest, TikTok, LinkedIn, YouTube, Reddit, Snapchat, Vero and/or whatever the hottest platform is at the time of reading.

What you are not looking for are glossy photos of their latest project, because these pictures could have come from anywhere and/or been edited. What you are looking for are two things:

  1. Consistency
    Look at whether the prospective builder’s messaging is the same across the website and across the aforementioned platforms they have an account on. If they’ve just gained an accreditation, are they shouting about it on LinkedIn? If they say they have a large team, do you see them hammering away on Insta?
  2. What else is going on in a post?
    On the latest Facebook post, was the worksite tidy or was there Maccy D’s packaging strewn across the floor? Often what you see in the background is the most telling.

To recap: the way to shortlist good builders for your project is to triangulate your research using recommendations, accreditations and social feeds. Doing so will give you credible insights to help you suss out whether a builder is worth pursuing for a quote. Shortlist five and prioritise the list, with your favourite (so far) at the top. Then have the top available three come over to quote.