Extension Costs by Trade: Every Trade Rate in 2026
Labour is 40-50% of your extension cost. Here are the actual daily rates for every trade involved in a London extension, compared to Midlands baseline rates - sourced from ConcreteMath 2024/25 data.
TL;DR
London trade rates run 35-45% higher than the Midlands across all 11 trades. The biggest premium is on electricians (£350-550/day London vs £250-400 Midlands). The smallest gap is on labourers (30% premium). On a typical 15m² rear extension, the labour cost difference between London and the Midlands is approximately £8,000-12,000. These rates are from ConcreteMath's 2024/25 survey - the most comprehensive trade rate dataset available in the UK.
£280-440
Builder day rate (London)
ConcreteMath 2024/25
£200-320
Builder day rate (Midlands)
ConcreteMath 2024/25
35-45%
London premium on trades
11
Trades on a typical extension
Source: ConcreteMath 2024/25 trade rate survey
Every Trade Rate: London vs Midlands
These are daily rates - what each tradesperson charges per day on site. Most tradespeople work 8-hour days. Rates vary by experience, complexity, and demand. The ranges below represent the typical spread from a competent but standard tradesperson (low end) to highly experienced specialists (high end).
| Trade | Midlands (low) | Midlands (high) | London (low) | London (high) | Premium |
|---|---|---|---|---|---|
| General Builder | £200 | £320 | £280 | £440 | +38% |
| Electrician | £250 | £400 | £350 | £550 | +38% |
| Plumber | £250 | £375 | £350 | £500 | +37% |
| Carpenter | £200 | £300 | £275 | £400 | +35% |
| Plasterer | £200 | £300 | £250 | £400 | +30% |
| Roofer | £200 | £350 | £300 | £450 | +36% |
| Bricklayer | £200 | £300 | £280 | £400 | +36% |
| Groundworker | £175 | £275 | £250 | £375 | +39% |
| Decorator | £150 | £250 | £200 | £350 | +38% |
| Tiler | £200 | £300 | £250 | £400 | +30% |
| Labourer | £100 | £150 | £130 | £200 | +32% |
Source: ConcreteMath • Data as of 2024/25 rates
Trade-by-Trade Breakdown
General Builder
Your main contractor. On site for the majority of the build - foundations, blockwork, structural openings, general coordination. London: £280-440/day. A 15m² rear extension typically needs 30-40 builder days, so labour alone is £8,400-17,600 in London.
Electrician
The most expensive trade per day. First fix (running cables before plastering) plus second fix (sockets, switches, lights, consumer unit upgrade). A typical extension needs 3-5 electrician days at £350-550/day in London. Part P certification adds £200-400.
Plumber
Heating extensions, radiator repositioning, underfloor heating, and any new bathroom or utility plumbing. 3-6 days for a kitchen extension at £350-500/day in London. If you're adding underfloor heating, add 2-3 days.
Bricklayer
External walls, cavity walls, and any blockwork above DPC. A bricklayer typically lays 400-500 bricks per day. A 15m² extension with 2.4m walls needs roughly 8-12 bricklayer days at £280-400/day in London.
Roofer
Flat roof (most common for rear extensions) or pitched roof connection to the existing house. A flat roof on a 15m² extension takes 2-3 days at £300-450/day in London. Loft conversions obviously need far more roofing work - 5-10 days.
How Labour Fits Into Total Cost
On a typical London extension, the cost breakdown is approximately:
| Component | % of total | 15m² extension (London) |
|---|---|---|
| Labour | 40-50% | £28,000-£37,500 |
| Materials | 25-30% | £17,500-£22,500 |
| Professional fees | 10-15% | £7,000-£11,250 |
| Kitchen/bathroom fit-out | 10-20% | £7,000-£15,000 |
| VAT (20%) | - | £12,500-£17,500 |
| Contingency (10%) | - | £6,250-£8,750 |
Source: Mayfair Studio cost model • Data as of 2026
This means a typical 15m² rear extension in London costs £70,000-95,000 all-in. Of that, roughly £28,000-37,500 is labour across all trades. In the Midlands, the same extension is £52,000-70,000 with labour at £20,000-27,000.
Regional Cost Multipliers
Our composite model averages ConcreteMath trade multipliers (labour-weighted) with Costmodelling construction indices to produce a single cost multiplier per region. The Midlands is the baseline at 0.98.
| Region | Multiplier | Cost/m² (build only) | 15m² rear (build) |
|---|---|---|---|
| Inner London | 1.25 | £3,000 | £45,000 |
| Outer London | 1.22 | £2,928 | £43,920 |
| South East | 1.14 | £2,736 | £41,040 |
| South West | 1.06 | £2,544 | £38,160 |
| East of England | 1.05 | £2,520 | £37,800 |
| East Midlands | 0.98 | £2,352 | £35,280 |
| West Midlands | 0.98 | £2,352 | £35,280 |
| North West | 0.96 | £2,304 | £34,560 |
| Wales | 0.96 | £2,304 | £34,560 |
| Yorkshire & Humber | 0.95 | £2,280 | £34,200 |
| North East | 0.90 | £2,160 | £32,400 |
Source: ConcreteMath + Costmodelling composite model • Data as of 2024/25
Seasonal and Market Factors
Trade rates are not fixed - they fluctuate with demand, season, and market conditions. Key factors:
- •Spring/summer premium: Trade rates can be 5-15% higher between April and September when demand peaks. Starting a build in October-January often gets more competitive quotes.
- •Material cost volatility: Post-2020 material costs have stabilised somewhat but remain 15-25% above 2019 levels. Timber, steel, and insulation have seen the biggest increases.
- •Builder availability: Good builders in London are typically booked 3-6 months ahead. Urgency can add 10-20% to quotes. Planning early gives you negotiating power.
Frequently Asked Questions
How much does a builder charge per day in London?
A general builder charges £280-440 per day in London, based on ConcreteMath 2024/25 survey data. This is approximately 38% more than the Midlands rate of £200-320/day. The rate depends on experience, the complexity of the work, and current demand.
What is the most expensive trade on an extension?
Electricians are the most expensive trade per day, at £350-550/day in London. However, they are typically on site for fewer days (3-5) than the general builder (30-40 days), so the builder represents the largest overall labour cost.
How much of an extension cost is labour?
Labour accounts for approximately 40-50% of total extension costs. On a typical £75,000 London extension, that is £30,000-37,500 across all trades. The remainder covers materials (25-30%), professional fees (10-15%), and fit-out/finishes.
Are extension costs cheaper outside London?
Yes. Our regional cost model shows Inner London at a 1.25x multiplier versus the Midlands baseline. The cheapest region is the North East at 0.90x. A 15m² rear extension costs approximately £45,000 (build only) in inner London versus £32,400 in the North East - a 39% difference.
How many trades are involved in a typical extension?
A typical rear extension involves 11 different trades: general builder, electrician, plumber, carpenter, plasterer, roofer, bricklayer, groundworker, decorator, tiler, and labourer. Some trades may be covered by the main contractor's team rather than separate subcontractors.