How to Price a Two-Storey Extension in the UK

Introduction

Pricing a two-storey extension is one of the trickier quotes you'll put together. Get it wrong and you're either losing the job or losing money on it. The margins are real, and the variables are many. This guide walks you through a practical, no-nonsense approach to building your quote — from groundworks to roof — so you know what to charge and why.

Why Two-Storey Extensions Are Harder to Price Than Single-Storey

A single-storey extension is relatively straightforward. A two-storey job adds complexity at every level — literally.

You're looking at more structural work, additional scaffolding time, roof structure, first-floor joists, staircase alterations, and often more disruption to the existing building. Each one of those adds cost and risk.

Clients often assume the price is just double a single storey. It isn't. Make sure your quote reflects the real scope.

Key Cost Categories to Include in Your Quote

Break your price down into clear categories. This helps you build an accurate number and makes the quote easier for clients to follow.

1. Groundworks and foundations: Strip foundations, concrete, drainage diversions. Expect £8,000–£20,000+ depending on ground conditions and size. Always flag that this is subject to ground investigation — surprises underground kill margins.
2. Structural frame and walls: Blockwork, cavity insulation, wall ties, lintels. Factor in the extra load-bearing requirements of two storeys. You may need steel beams where a single storey wouldn't.
3. First-floor structure: Joists, noggins, flooring deck, and any steel needed to support the upper floor. Don't underestimate this — it's often where quotes fall short.
4. Roof: Pitched or flat? Each has a different cost profile. A pitched roof with tiles will cost more upfront but has fewer long-term issues. Budget £10,000–£20,000 for a moderate-sized pitched roof including structure, felt, battens, and tiles.
5. Windows and external doors: UPVC, aluminium, or timber — all different price points. Always get a supplier quote locked in before you submit your price.
6. Internal fit-out: Plastering, first fix, second fix, floor finishes, decoration. This is where spec variation hits hardest. A budget finish vs a premium finish can vary by £20,000 or more on a mid-size job.
7. Mechanical and electrical: Heating, plumbing, electrics. If you're subbying this out, get firm quotes before you commit to a price. M&E is one of the biggest sources of variation on extension jobs.
8. Scaffolding: Two storeys means more scaffold, longer hire periods, and potentially more complex erection. Budget £3,000–£7,000 and confirm this with your scaffolder before quoting.
9. Prelims and site costs: Skips, welfare, site protection, temporary works. These are easy to forget but they add up fast on a longer project.
10. Professional fees and building regs: Structural engineer, building control fees, and any planning-related costs. These are usually the client's responsibility, but make it clear in your quote if that's the case.

How to Calculate Your Labour Costs

Labour is where most tradespeople either over- or under-price. Here's a simple approach:

1. List every trade required — groundworkers, bricklayers, carpenters, roofers, plasterers, electricians, plumbers, decorators.
2. Estimate the days required for each trade based on the scope. Be realistic, not optimistic.
3. Multiply by your day rate or the going rate in your area. Day rates vary significantly — London and the South East run higher than the Midlands or North.
4. Add a contingency of 10–15% on labour. Projects always take longer than planned.

Don't guess labour. If you're unsure on a particular element, price it as a provisional sum and be transparent with the client.

Regional Price Differences in the UK

Location has a significant impact on what you can and should charge.

In London and the South East, a two-storey extension can command £2,000–£2,500 per m² or higher for good-quality work. In the Midlands and North, you're more likely to be pricing in the £1,500–£1,900 per m² range.

This affects both what you charge and what your subbies and suppliers charge you. Always use local benchmarks, not national averages from a magazine article.

Your Margin: Don't Forget to Include It

This sounds obvious, but many tradespeople price their costs and forget to properly add margin on top.

Overhead and profit should be built into every quote. As a minimum, aim for 15–20% gross margin on a project of this size. If you're managing the job, carrying risk, and dealing with the client — you've earned it.

A good rule: once you've totalled your costs, apply your overhead contribution and then your net profit separately. Know what you're making before you submit.

Use the Right Tools to Speed Up Your Quoting

Building a detailed quote for a two-storey extension from scratch takes time. If you're doing this manually on a spreadsheet, you're spending hours that could go into the next job.

MyQS is built for UK tradespeople and builders who want to produce accurate, professional quotes faster. It lets you build out itemised estimates by trade and category, apply your own rates, and produce a clean client-facing document — without starting from a blank sheet every time. If you're quoting extensions regularly, it's worth looking at myqs.ai.

5 Practical Tips for Pricing Two-Storey Extensions

1. Always do a full site visit before quoting. Ground conditions, access, existing structure, and party wall issues can all change your number significantly.
2. Get subbies to quote before you commit. Never estimate M&E, scaffolding, or specialist groundwork from memory on a job of this size.
3. Use provisional sums where there's genuine uncertainty. It protects you and it's honest. Clients appreciate transparency more than a fixed price that blows up later.
4. Include a clear payment schedule. Deposits, stage payments tied to milestones, and a retention if appropriate. Don't carry a two-storey extension on your own cash.
5. Review your quote against the drawings before sending. Scope creep starts at the quoting stage. Make sure what you've priced matches what's on the plan.

FAQ

How long does it take to build a two-storey extension in the UK?

Most two-storey extensions take between 4 and 6 months from start to completion, depending on size, spec, and weather. Factor this into your programme and your prelims costs when pricing.

Do I need planning permission for a two-storey extension?

In most cases, yes. Two-storey rear extensions are not covered by permitted development. Your client will need full planning permission. Make sure this is in place before you start work — and make it clear in your contract that it's the client's responsibility to obtain.

What's the most common reason two-storey extension quotes go wrong?

Underpricing groundworks and M&E. Both are heavily influenced by site-specific conditions that are hard to assess without investigation. Always include a contingency, use provisional sums where appropriate, and get specialist quotes before committing to a fixed price.

Conclusion

Pricing a two-storey extension well is about discipline — breaking the job down properly, getting real numbers from subbies and suppliers, knowing your rates, and adding your margin without apology.

Do it right and you'll win the right jobs at the right price. Do it fast on a gut feel and you'll regret it by month three.

If you want to quote faster and more accurately, visit myqs.ai and see how it can take the friction out of your estimating process.