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Due diligence when selecting a builder

11 replies

DeliciouslyBaked · 23/01/2026 14:46

We are planning a small kitchen extension, plus opening up the existing space to have room to fit a dining table in rather than our existing galley kitchen. We are sorted on how we are paying for it and we've had high level plans drawn up.

I've been reading all about what due diligence to do when contacting builders - we are being cautious about those who can start straight away, we've asked around for recommendations, we've asked for three references. It's still proving an absolute nightmare to know who to trust.

One thing i keep seeing is about checking Companies House, but what exactly should i be looking for? I can look at their accounts and but i've no idea how to read them properly. It's not something i've ever had to do. Should i be looking for a certain about of assets in the business? Or is there something else i should be looking for?

Is there a good trustworthy website that explains this stuff to an idiot? All the checklists i've been looking at say things like "check Companies House". I need more info than that!

OP posts:
NoWinnersOnlyLosers · 23/01/2026 14:50

Did not want to read and run. I asked chat gpt and this is what it came up with:

You’re not an idiot — this is genuinely opaque, and most “check Companies House” advice is lazy shorthand. I’ll break it down in plain English and tell you what actually matters (and what doesn’t) when you’re hiring a builder for a domestic extension in the UK.

Short version first:
👉 Companies House is a risk filter, not a trust guarantee.
You’re looking for red flags, not “proof they’re good”.

Step 1: What type of builder are they?

Before you even look at accounts, check what you’re dealing with:

1️⃣ Limited company (Ltd)

  • Appears on Companies House
  • Separate legal entity
  • If it collapses, you can’t easily chase the director personally

2️⃣ Sole trader

  • Often won’t appear on Companies House
  • Much more common for good local builders
  • Due diligence looks different (insurance, references, contracts matter more)

⚠️ Important:
A Ltd company is NOT safer than a sole trader by default.
Some of the worst cowboy builders use Ltd companies precisely because they can walk away from them.

Step 2: What you should ACTUALLY check on Companies House

When you search a builder’s Ltd company, focus on these 6 things only:

✅ 1. How long has the company existed?

Look for:

  • Ideally 3+ years
  • 5+ years is a strong positive

Red flags:

  • Company formed in the last 6–18 months
  • Especially if the director has run other dissolved companies

Why it matters: Fly-by-night builders often close one company and open another.

✅ 2. Director history (this is BIG)

Click the director’s name → “Appointments”

Good signs:

  • One company
  • Long-running
  • No dissolved trail

Red flags:

  • Multiple dissolved companies
  • Pattern of companies lasting 1–3 years then closing
  • Several companies with similar names (e.g. “Smith Build Ltd”, “Smith Building UK Ltd”)

🚨 This matters more than the accounts.

✅ 3. Company status

You want:

  • Active
  • Accounts and confirmation statements filed on time

Red flags:

  • Overdue filings
  • “Proposal to strike off”
  • Repeated late filings (shows disorganisation at best)

✅ 4. Accounts: what to look for (simple version)

Ignore the scary spreadsheets. You only need to answer three questions:

a) Are they filing
micro-entity
accounts?

  • Totally normal for builders
  • Doesn’t mean they’re small or bad

b) Are they insolvent?

Look for:

  • Net assets NOT negative

If you see:

  • “Net liabilities” or “(£X)” in brackets → 🚩

A small positive number is fine. Builders don’t hold lots of cash.

c) Do the numbers look vaguely consistent?

  • £100k turnover one year, £10k the next, £200k after → questionable
  • Rough stability is what you want

⚠️ Do NOT expect big assets or cash reserves
Most builders:

  • Lease vans
  • Rent equipment
  • Have thin margins

Big assets ≠ trustworthy builder.

✅ 5. Charges (loans against the company)

Under “Charges”:

  • None or historic = fine
  • Current charges = not necessarily bad

But:

  • Multiple lenders
  • Recent emergency finance
  • → mild warning sign

✅ 6. Registered address

Normal:

  • Accountant’s office
  • Home address

Red flag:

  • Frequent changes
  • Virtual office + no physical presence + new company

Step 3: What Companies House DOESN’T tell you (but matters more)

Honestly? These are often more important:

🔧 Current jobs you can visit

Ask:

“Are any of your current or just-finished jobs local that we could see?”

A good builder:

  • Will happily show you
  • Might even introduce you to the client

A bad one:

  • Makes excuses
  • Only shows glossy photos

📞 References — but ask the RIGHT questions

Don’t just ask “were they good?”

Ask:

  • Did the final cost match the quote?
  • How did they handle problems?
  • Was the site tidy?
  • Would you use them again without hesitation?

Listen for tone, not words.

📄 Contract + payment structure

Massive green flag if they:

  • Use a written contract
  • Stage payments tied to milestones
  • Ask for small deposit only (5–10%)

🚩 Red flags:

  • Large upfront payments
  • Cash discounts
  • “Don’t worry, we don’t need paperwork”

Step 4: About “builders who can start straight away”

You’re right to be cautious — but nuance matters:

Red flag:

  • “I can start Monday” with no site visit, no detailed quote

Green-ish explanation:

  • A job delayed
  • A cancellation
  • They’re between phases

Ask why — confidence + specifics are reassuring.

Step 5: A genuinely good plain-English resource

You’re not imagining it — most guides are awful.

These are actually decent and UK-specific:

  • Which? Trusted Traders – especially their questions to ask builders articles
  • Citizens Advice – boring but accurate, especially contracts & payments
  • Federation of Master Builders (FMB) – their guidance pages are better than their membership badge

(Builder membership badges alone mean nothing — guidance > logos.)

Bottom line (this is the part most lists won’t tell you)

If I had to rank trust signals for a kitchen extension:

1️⃣ Seeing current/finished work
2️⃣ Quality of references
3️⃣ Sensible contract & payment terms
4️⃣ Director history on Companies House
5️⃣ Accounts being solvent
6️⃣ Badges / memberships (last place)

ResusciAnnie · 23/01/2026 14:51

Best thing we trusted was our gut tbh. The builder we went with had no website/social media etc as didn’t have time for it and didn’t need it. All his work was through word of mouth. We had to wait a year for him to start. It was amazing throughout, 9 month project living in with 3 kids and a 1 year old. We basically chose him because he was a nice guy and we got very good vibes.

I hate choosing tradesmen, sympathies! Gut rarely wrong though. Facebook etc waste of time, don’t even bother, as people just shove on the name of their friends and family with zero actual detail into why they’d recommend.

Mumski45 · 23/01/2026 14:53

I think when checking companies house you should be checking that the owner/director does have a string of failed companies behind them which indicates that as soon as someone tries to make a claim against their company they close it down and start another one. I would be searching the shareholders names and the longevity of the company. Unless you are using a large company you will be unlikely to get any useful financial data from companies house due to limited filing requirements for small businesses.

Mumski45 · 23/01/2026 14:56

NoWinnersOnlyLosers · 23/01/2026 14:50

Did not want to read and run. I asked chat gpt and this is what it came up with:

You’re not an idiot — this is genuinely opaque, and most “check Companies House” advice is lazy shorthand. I’ll break it down in plain English and tell you what actually matters (and what doesn’t) when you’re hiring a builder for a domestic extension in the UK.

Short version first:
👉 Companies House is a risk filter, not a trust guarantee.
You’re looking for red flags, not “proof they’re good”.

Step 1: What type of builder are they?

Before you even look at accounts, check what you’re dealing with:

1️⃣ Limited company (Ltd)

  • Appears on Companies House
  • Separate legal entity
  • If it collapses, you can’t easily chase the director personally

2️⃣ Sole trader

  • Often won’t appear on Companies House
  • Much more common for good local builders
  • Due diligence looks different (insurance, references, contracts matter more)

⚠️ Important:
A Ltd company is NOT safer than a sole trader by default.
Some of the worst cowboy builders use Ltd companies precisely because they can walk away from them.

Step 2: What you should ACTUALLY check on Companies House

When you search a builder’s Ltd company, focus on these 6 things only:

✅ 1. How long has the company existed?

Look for:

  • Ideally 3+ years
  • 5+ years is a strong positive

Red flags:

  • Company formed in the last 6–18 months
  • Especially if the director has run other dissolved companies

Why it matters: Fly-by-night builders often close one company and open another.

✅ 2. Director history (this is BIG)

Click the director’s name → “Appointments”

Good signs:

  • One company
  • Long-running
  • No dissolved trail

Red flags:

  • Multiple dissolved companies
  • Pattern of companies lasting 1–3 years then closing
  • Several companies with similar names (e.g. “Smith Build Ltd”, “Smith Building UK Ltd”)

🚨 This matters more than the accounts.

✅ 3. Company status

You want:

  • Active
  • Accounts and confirmation statements filed on time

Red flags:

  • Overdue filings
  • “Proposal to strike off”
  • Repeated late filings (shows disorganisation at best)

✅ 4. Accounts: what to look for (simple version)

Ignore the scary spreadsheets. You only need to answer three questions:

a) Are they filing
micro-entity
accounts?

  • Totally normal for builders
  • Doesn’t mean they’re small or bad

b) Are they insolvent?

Look for:

  • Net assets NOT negative

If you see:

  • “Net liabilities” or “(£X)” in brackets → 🚩

A small positive number is fine. Builders don’t hold lots of cash.

c) Do the numbers look vaguely consistent?

  • £100k turnover one year, £10k the next, £200k after → questionable
  • Rough stability is what you want

⚠️ Do NOT expect big assets or cash reserves
Most builders:

  • Lease vans
  • Rent equipment
  • Have thin margins

Big assets ≠ trustworthy builder.

✅ 5. Charges (loans against the company)

Under “Charges”:

  • None or historic = fine
  • Current charges = not necessarily bad

But:

  • Multiple lenders
  • Recent emergency finance
  • → mild warning sign

✅ 6. Registered address

Normal:

  • Accountant’s office
  • Home address

Red flag:

  • Frequent changes
  • Virtual office + no physical presence + new company

Step 3: What Companies House DOESN’T tell you (but matters more)

Honestly? These are often more important:

🔧 Current jobs you can visit

Ask:

“Are any of your current or just-finished jobs local that we could see?”

A good builder:

  • Will happily show you
  • Might even introduce you to the client

A bad one:

  • Makes excuses
  • Only shows glossy photos

📞 References — but ask the RIGHT questions

Don’t just ask “were they good?”

Ask:

  • Did the final cost match the quote?
  • How did they handle problems?
  • Was the site tidy?
  • Would you use them again without hesitation?

Listen for tone, not words.

📄 Contract + payment structure

Massive green flag if they:

  • Use a written contract
  • Stage payments tied to milestones
  • Ask for small deposit only (5–10%)

🚩 Red flags:

  • Large upfront payments
  • Cash discounts
  • “Don’t worry, we don’t need paperwork”

Step 4: About “builders who can start straight away”

You’re right to be cautious — but nuance matters:

Red flag:

  • “I can start Monday” with no site visit, no detailed quote

Green-ish explanation:

  • A job delayed
  • A cancellation
  • They’re between phases

Ask why — confidence + specifics are reassuring.

Step 5: A genuinely good plain-English resource

You’re not imagining it — most guides are awful.

These are actually decent and UK-specific:

  • Which? Trusted Traders – especially their questions to ask builders articles
  • Citizens Advice – boring but accurate, especially contracts & payments
  • Federation of Master Builders (FMB) – their guidance pages are better than their membership badge

(Builder membership badges alone mean nothing — guidance > logos.)

Bottom line (this is the part most lists won’t tell you)

If I had to rank trust signals for a kitchen extension:

1️⃣ Seeing current/finished work
2️⃣ Quality of references
3️⃣ Sensible contract & payment terms
4️⃣ Director history on Companies House
5️⃣ Accounts being solvent
6️⃣ Badges / memberships (last place)

looks like chat gpt beat me to it but I agree with all of this.

Dontjumptoconclusions · 23/01/2026 15:09

when we chose our builder, we used a builder we saw doing some local work, they usually have their name and phone number on a board outside the house they are working on. Once they finished doing the renovation, we knocked on the house door and basically said we are looking at this builder would they recommend. And straight from the horses mouth they said the team were fantastic, completed on time to budget etc. And I trusted that review more than anything because they were under no obligation to say it was good.

Also keep an eye for builders who are available very quickly, there's usually a wait for good builders.

Get a contract drawn up and a payment schedule should be when they complete certain aspects of the job (not as a time frame of every week for example as things can take longer than anticipated but you would still be expected to pay them on time). Check if they are doing any other jobs or yours would be the only one they commit to.

And how they want to accept payment - we had one builder want £100k all in cash and he basically said it's because no one wants to pay VAT. Fair enough but when I looked, he wasn't even VAT registered, so it's not like there was even a choice even if I wanted to pay cash.

Get a few different quotes and listen to how they speak as well, you must feel comfortable with this person in your home and feel confident that you're relying on them to do the work.

Thunderdcc · 23/01/2026 15:11

We have had a fair amount of work done on our house and to be honest gut instinct goes a long way. If they make you feel stupid or like you don't understand what they are explaining then bin them that is no good. You need to be able to understand when inevitably they find a problem and you get the dreaded "can we have a quick chat" 😂

Kwamitiki · 23/01/2026 15:44

We actually found our builders by asking neighbours who had had building work. Our neighbour has a son who is a tradesman and he was very helpful in suggesting names and confirming reputations.

Before he helped us out, we also drove around to see what work was going on locally. Really helped us to have an idea.

It also turned out that one of DDCs friends parents had had work done recently, and they were open about who they used, and also let us see the work. Very much confirmed who to go for as we had two quotes that looked good and that we had a good feeling about!

ResusciAnnie · 23/01/2026 15:56

Kwamitiki · 23/01/2026 15:44

We actually found our builders by asking neighbours who had had building work. Our neighbour has a son who is a tradesman and he was very helpful in suggesting names and confirming reputations.

Before he helped us out, we also drove around to see what work was going on locally. Really helped us to have an idea.

It also turned out that one of DDCs friends parents had had work done recently, and they were open about who they used, and also let us see the work. Very much confirmed who to go for as we had two quotes that looked good and that we had a good feeling about!

Edited

Yep that’s the best way, we’ve had a couple of people get in touch to talk about our builder. If your potential builder wouldn’t be willing to put you in touch with willing past clients then that’s a red flag.

DeliciouslyBaked · 24/01/2026 14:38

Oh my word everyone, thank you so much for all this amazing advice. Going to try and grab some time away from the DC to concentrate and read properly.

OP posts:
HappiestSleeping · 24/01/2026 14:44

Insurance. Not just for while they are on the premises, but also if their work turns out to be shit. We spent over £100k having our garden and driveway done, part of it was a retaining wall.

It has since started to subside. Original contractor admitted that the work was sub standard, but just said "our insurance doesn't cover poor workmanship", and tried to charge me to out it right.

We went through the house insurance legal who agreed we would win, but they wouldn't take it on as they knew the builder would just flip his company and none of us would get anything. We couldn't afford to pursue it ourselves, so they got away with it.

ScaredAndSkint · 24/01/2026 14:52

Apologies for jumping on an existing thread.
What do you do if your house needs structural repairs? Presumably I need to tell the insurers, get a structural surveyor then a few quotes.

Any advice please.

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