SiteKiln gives you plain-English information, not legal advice. If you need advice specific to your situation, talk to a qualified accountant, solicitor or HR adviser.
Scaling isn't magic, it's just adding people and systems -- and each step wakes up a new bit of law. Here's how to think about it.
1. Stage 1: one-man band with regular help
You're here if it's mainly you, with the odd mate or subbie.
Key points:
- You can be sole trader or limited company -- structure choice is mainly about tax and risk at this stage.
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Legal basics:
- Register for Self Assessment and, if in construction, CIS (as subbie and/or contractor).
- Watch the VAT threshold -- once turnover tips over about £90k in any 12 months, you must register.
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If you're using subbies, you still need to:
- Get their details, verify them for CIS if you're the contractor.
- Check status -- don't treat employees as "cash-in-hand subbies" (see 8.4 and 8.10).
At this stage, your main "scaling" jobs are: keep clean books, use a separate account, and don't wing CIS or VAT.
2. Stage 2: first proper employee (1-4 staff)
Once you put someone on the books, the game changes.
You must:
- Decide their status correctly (employee vs worker vs self-employed).
- Register as an employer with HMRC and set up PAYE.
- Sort employers' liability insurance.
- Give them a written statement / contract covering pay, hours, holidays, etc. (Employment Rights Act 1996).
- Pay at least the National Minimum/Living Wage and give statutory holiday.
- Trigger auto-enrolment pension duties if they're an eligible jobholder (22 to State Pension Age, over £10k a year).
H&S wise, you still don't legally need a written policy below 5 staff, but in construction it makes sense to have at least a basic one (see 8.11).
3. Stage 3: hitting 5+ employees -- key legal thresholds
5 is a big number in UK compliance.
Once you hit 5 or more employees at any time:
- Written health & safety policy becomes mandatory -- statement, organisation, and arrangements for managing risk.
- You must also record the significant findings of your risk assessments and bring the policy to staff's attention.
On the HR side, 5+ staff is also where people start expecting:
- A more formal staff handbook -- basic policies on conduct, grievance, discipline, equality, etc.
- Some structure to holidays, sickness, overtime and training.
Auto-enrolment and PAYE don't change at 5 -- they kicked in with your first employee -- but the paper trail and expectations do.
4. Stage 4: VAT, company accounts and "bigger business" rules
Separately from headcount, there are financial thresholds to watch as you grow:
- VAT registration -- compulsory once taxable turnover in any rolling 12 months goes over about £90,000 (current UK threshold around that mark), which is common in construction.
- Company size thresholds -- if you're Ltd, recent changes increased "small/medium" cut-offs; most small construction firms will sit in the small company zone, with lighter reporting than medium/large.
As you grow you may also start tripping:
- Audit thresholds -- medium/large companies need audits; most small firms won't be there, but know it exists.
- More serious Companies House scrutiny -- late accounts, repeated penalties, and messy filings look worse when you're a bigger employer (see 8.2).
This is where having a switched-on accountant and proper bookkeeping stops being a "nice to have".
5. Practical scale-up steps at each stage
Going from 1 to 2-3 people
- Formalise: separate bank account, basic H&S policy, simple employment contracts, payroll sorted.
- Get your auto-enrolment and EL insurance right from hire one.
Going from 3 to 5 people
- Tighten H&S: draft the full written policy and start recording risk assessments properly.
- Put in basic systems: job sheets, variation forms, timesheets, toolbox talks.
Going from 5 to 10+ people
- Consider moving to a Ltd company if you're not already (risk and tax reasons).
- Add some light management structure -- working foreman, someone handling office/admin.
- Get your HR and H&S paperwork reviewed by a professional (you don't need ISO badges, just not-cowboy).
At each jump, the trick is to get ahead of the threshold -- don't wait until the week you hire person number five to think about policies.
Scale-up ladder for a small builder
Step 1 -- One-man band (0-1 on the books)
You: just you, maybe the odd casual helper or genuine subbie.
- Get the basics right: Self Assessment/CIS registration, separate bank account, clean records.
- Make sure any "subbies" are genuinely self-employed and, if you're the contractor, you're registered for CIS and verifying them.
- Keep an eye on the VAT threshold -- once turnover heads towards ~£90k in 12 months, talk to your accountant.
Step 2 -- Small crew (1-4 employees)
You: you plus 1-4 people on payroll.
- Register as an employer and run PAYE properly -- no cash-in-hand shortcuts.
- Put in written contracts and basic HR records (right to work, pay, holidays, sickness).
- Get employers' liability insurance and check your public liability still fits the bigger risk.
- Start your auto-enrolment duties and keep up pension contributions.
- Have at least a simple H&S policy and RAMS, even though under 5 you don't legally have to write it all down.
Step 3 -- Proper small firm (5-10 employees)
You: 5+ on the books, regular jobs on the go.
- Written health & safety policy now mandatory by law; plus written risk assessment findings.
- Build a basic staff handbook -- discipline, grievance, equality, holiday/sickness rules.
- Tighten up job management: standard quotes, variations forms, site files, toolbox talks.
- Make sure VAT, CIS, PAYE and pensions are all up to date -- no more winging it.
Step 4 -- Growing outfit (10+ employees and/or higher turnover)
You: several gangs, possibly multiple sites at once.
- Review your business structure -- likely Ltd, possibly group structure as you grow.
- Keep an eye on company size thresholds -- you'll stay "small" for a while, but reporting will get heavier as you climb.
- Bring in more management: foremen, someone dedicated to H&S/admin, serious bookkeeping and management accounts.
- Start thinking strategically about frameworks, tenders and bigger clients -- the compliance work you've done now starts to pay off.
If you climb this ladder one step at a time -- not trying to do step 4 jobs at step 1 -- you massively cut the risk of nasty surprises from HMRC, HSE or Companies House.
6. Common mistakes
- Growing headcount without growing systems -- 10 lads and no timesheets, no proper contracts, no written H&S policy. One HSE visit or HMRC enquiry and you're in trouble.
- Ignoring the VAT threshold until HMRC writes to you -- then you owe backdated VAT and penalties.
- Treating everyone as self-employed to avoid PAYE and pensions -- HMRC's favourite thing to investigate in construction.
- Not reviewing insurance as you grow -- your £1m PL policy from when it was just you might not cover a 10-person operation.
- Trying to run a 10-person firm from your phone -- at some point you need proper software, proper admin, and someone who isn't you doing the books.
7. Who to contact
- HMRC VAT helpline -- 0300 200 3700 (free)
- HMRC employer helpline -- 0300 200 3200 (free)
- The Pensions Regulator -- auto-enrolment duties: thepensionsregulator.gov.uk (free)
- HSE -- employer health and safety duties: hse.gov.uk (free)
- ACAS -- employment rights, contracts and HR basics: 0300 123 1100 (free)
- Your accountant -- structure advice, VAT timing, payroll setup
- FMB / NFB -- trade body support for growing construction firms
8. Sources and legislation
- Health and Safety at Work etc. Act 1974 -- section 2(3) (written policy at 5+ employees). legislation.gov.uk/ukpga/1974/37
- Employment Rights Act 1996 -- written statement of particulars (day 1 right). legislation.gov.uk/ukpga/1996/18
- Employers' Liability (Compulsory Insurance) Act 1969 -- EL insurance requirement. legislation.gov.uk/ukpga/1969/57
- Pensions Act 2008 -- auto-enrolment duties. legislation.gov.uk/ukpga/2008/30
- Value Added Tax Act 1994 -- VAT registration thresholds. legislation.gov.uk/ukpga/1994/23
- Companies Act 2006 -- company size thresholds, filing requirements. legislation.gov.uk/ukpga/2006/46
9. Related guides on this site
- 8.1 Sole trader vs limited company -- honest comparison
- 8.2 Companies House basics -- annual filings, confirmation statements
- 8.3 Business bank account -- why you need a separate one
- 8.4 Registering for CIS as a contractor
- 8.10 Taking on your first employee -- legal checklist
- 8.11 Health and safety policy -- when you need a written one
- 8.17 Partnerships in construction -- how to structure them properly
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