Total build budget: calculating every cost line
You know the cost per m² of your build, but the total budget for a house project goes well beyond that. Land, legal fees, service connections, planning levies, landscaping, fitted kitchen… The “forgotten” line items often represent 20 to 30 % of the real budget. This article gives you the method to price everything, line by line, with no nasty surprises.
The 8 cost lines of a total build budget
1. The land (plot)
This is often the most variable line. Prices per m² depend on location:
| Zone | Average price per m² | 500 m² plot |
|---|---|---|
| Rural | £5–20/m² | £2,500–10,000 |
| Suburban | £30–80/m² | £15,000–40,000 |
| Edge of city | £80–200/m² | £40,000–100,000 |
| High-demand area (London, SE, coast) | £200–500+/m² | £100,000–250,000+ |
Tip — The land should not exceed 30 to 35 % of the total budget. If you spend 50 % on the plot, there will not be enough left to build properly. This is the number one rule of budget balance.
2. Stamp Duty Land Tax (SDLT) and legal fees
When buying a plot, you pay Stamp Duty Land Tax plus solicitor and conveyancing fees:
| Plot price | SDLT (self build first home relief may apply) | Solicitor fees (est.) |
|---|---|---|
| £50,000 | £0–1,250 | ~£1,500 |
| £100,000 | £0–2,500 | ~£1,800 |
| £200,000 | £1,500–5,000 | ~£2,200 |
On serviced plots in a development, some fees may be reduced. Always confirm before exchanging contracts.
3. The build itself
Build cost depends on the route chosen and finish level. Current UK ranges:
| Route | Cost per m² | 120 m² house |
|---|---|---|
| Full self build (labour only) | £700–1,200/m² | £84,000–144,000 |
| Part self build | £1,200–1,800/m² | £144,000–216,000 |
| Main contractor | £1,600–2,400/m² | £192,000–288,000 |
| Architect-led bespoke | £2,200–3,500+/m² | £264,000–420,000+ |
This line covers: foundations, walls, roof structure, roofing, windows and doors, insulation, electrical, plumbing, plasterboard, tiling, painting and decorating.
4. Services and utility connections
If your plot has no existing services (common on rural plots), every utility must be connected:
| Connection | Typical cost | Variables |
|---|---|---|
| Water (mains) | £1,500–4,000 | Distance to main |
| Electricity (DNO) | £1,500–5,000 | Load, distance |
| Mains sewerage | £2,000–6,000 | Distance, depth |
| Private sewage treatment plant | £6,000–18,000 | System type, ground conditions |
| Broadband / fibre | £200–500 | Often free on developments |
| Total connections | £5,000–33,000 |
Warning — On an isolated rural plot, utility connections can reach £33,000 or more if mains infrastructure is far away. Get quotes before buying the plot. It is a decisive selection criterion — read our guide on how to choose a building plot.
5. Taxes and planning levies
Community Infrastructure Levy (CIL) and Section 106
These are charges payable to the local authority when you build. Calculation varies by council:
Chargeable floor area × CIL rate × Index factor
- CIL rate: £0–200+/m² depending on the local authority (some areas have £0 CIL)
- Section 106 agreements: negotiated on a case-by-case basis; can be £0 or several thousand pounds
- Check your local authority’s Charging Schedule before budgeting
Example for a 120 m² house at a CIL rate of £50/m²:
120 × £50 = £6,000
Other charges
| Charge | Amount | When |
|---|---|---|
| CIL / S106 | £0–24,000+ | On commencement of works |
| Planning application fee | £578 (householder) / £734 (new dwelling) | On submission |
| Building Regulations application | £500–1,200 | Before works begin |
| Council Tax (first year) | Exempt during build | After completion |
6. Professional fees and surveys
| Service | Cost | Required? |
|---|---|---|
| Architect (design + contract admin) | 8–12 % of build cost | Recommended; mandatory for complex projects |
| Architectural technician / drawings | £2,000–6,000 | If no architect |
| Structural engineer | £1,500–4,000 | Strongly recommended |
| Ground investigation (Phase 2) | £1,500–4,000 | Highly recommended |
| Boundary survey | £800–2,000 | If no recent survey |
| Self build warranty / structural guarantee | £3,000–10,000 | Required by most mortgage lenders |
7. External works and landscaping
Often underestimated, these costs arrive at the end of the project when the budget is already stretched:
| Item | Typical cost |
|---|---|
| Boundary fencing (500 m² plot) | £3,000–10,000 |
| Gates + automation | £2,000–7,000 |
| Driveway (concrete / gravel) | £2,500–7,000 |
| Patio / decking (30 m²) | £3,000–12,000 |
| Turfing and planting | £1,500–6,000 |
| Garden shed / carport | £1,500–6,000 |
| Total external works | £13,500–48,000 |
8. Interior fittings and equipment
| Item | Typical cost |
|---|---|
| Fitted kitchen (supplied and installed) | £5,000–25,000 |
| Bathroom (furniture, taps, sanitaryware) | £2,500–10,000 |
| Wardrobes and storage | £1,000–6,000 |
| White goods / appliances | £2,000–6,000 |
| Total fittings | £10,500–47,000 |
The total budget: a worked example
Here is a realistic example for a 120 m² house in a suburban location, part self build:
| Line item | Amount |
|---|---|
| Plot (500 m², £160/m²) | £80,000 |
| SDLT + solicitor fees | £6,000 |
| Build works (£1,500/m²) | £180,000 |
| Service connections | £8,000 |
| CIL / Building Regs fees | £6,500 |
| Ground survey + boundary survey | £3,500 |
| Self build warranty | £5,000 |
| External works | £15,000 |
| Kitchen + bathroom + fittings | £18,000 |
| Sub-total | £322,000 |
| Contingency (10 %) | £32,200 |
| TOTAL BUDGET | ~£354,000 |
Best practice — The 10 % contingency is not optional. On any construction project, the unexpected is the rule, not the exception: ground harder than anticipated, material price rises, measurement errors, design changes mid-build. Read our next article on managing build contingency.
The ideal budget split
If your plot exceeds 35 % of the total budget, you either need to find a cheaper plot or reduce the floor area of the house.
Budget and borrowing capacity: starting from the right end
The right approach is to start from your maximum borrowing capacity and work down, not up:
- Talk to your bank or a mortgage broker → maximum borrowing capacity.
- Add your deposit / equity → total available budget.
- Deduct plot + fees → build envelope.
- Deduct ancillary costs (15 %) → net build budget.
- Divide by cost per m² → achievable floor area.
Example: borrowing capacity £280,000 + deposit £50,000 = £330,000.
- Plot + fees (30 %): £99,000
- Ancillary costs + contingency (20 %): £66,000
- Build works: £165,000 → 120 m² at £1,375/m² (part self build)
Tip — Never build your budget by starting with the dream house and adding the cost lines on top. You will overshoot every time. Start from what you can borrow, deduct everything else, and see what is left for the build. This is the method described in our article on defining your build budget.
Key takeaways
The total cost of a house is not just the build contract. The ancillary lines (land, legal fees, levies, connections, external works, fittings) typically represent 40 to 55 % of the total outlay. Pricing them from the outset is the only way to avoid hitting a financial wall mid-build.
Checklist: total build budget
- Borrowing capacity confirmed (bank or broker)
- Plot price agreed (including SDLT and legal fees)
- Build cost estimated per m² (based on chosen route)
- Service connections quoted (DNO, water, drainage)
- CIL / S106 liability checked with local authority
- Professional fees listed (architect, engineer, surveyor, ground investigation)
- Self build warranty / structural guarantee budgeted
- External works costed (fencing, driveway, patio)
- Interior fittings budgeted (kitchen, bathrooms, appliances)
- 10 % contingency added
- Land / build split is healthy (30 / 50 / 20)