Quoting a loft conversion is one of the most common — and most misquoted — jobs in residential building. Get it wrong and you're working for nothing. Get it right and loft conversions are some of the most profitable jobs you'll take on.
This guide walks through exactly how to price a loft conversion so you protect your margin from the first number you put on paper.
Step 1: Understand What Type of Loft Conversion It Is
Not all loft conversions are equal. Before you price anything, establish the type:
- Roof light / Velux conversion — The most affordable. No structural change to the roofline, just windows and internal staircase. Typically £20,000–£35,000.
- Dormer conversion — A box-shaped extension to the roof. Most common. Adds significant floor space. Typically £35,000–£60,000.
- Hip-to-gable conversion — Extends the sloped side of a roof to create a vertical wall. Often combined with a dormer. Typically £40,000–£65,000.
- Mansard conversion — Changes the entire roof structure. Most complex and expensive. Typically £50,000–£80,000+.
Each type has fundamentally different labour and structural requirements. Confirm the type before doing any detailed pricing.
Step 2: Break Down the Cost Categories
A well-structured loft conversion quote should cover these cost areas:
Structural Works
- Steel beams (RSJs) — typically £800–£1,500 per beam fitted
- Floor joists / structural floor — £3,000–£6,000 depending on span
- Structural engineer fees — £500–£1,200
- Party wall agreements (if required) — £700–£1,500 per neighbour
Roofing Works
- Dormer frame and flat roof — £4,000–£8,000
- Roof tiles / slates to match existing — price varies significantly by tile type
- Velux windows — £800–£1,500 each supplied and fitted
- Scaffolding — £1,500–£3,000 for a standard semi
Internal Works
- Staircase — £2,500–£5,000 (bespoke timber)
- Insulation (roof, walls, floor) — £1,500–£3,000
- Plasterboard and plastering — £2,000–£4,000
- Electrical first and second fix — £1,500–£2,500
- Plumbing (if en-suite) — £2,000–£4,000
- Flooring — price per m² based on client spec
Step 3: Calculate Your Labour Costs Accurately
Labour is where most builders lose money on loft conversions. The common mistake is estimating days without accounting for access difficulty, material hoisting, or weather delays on roofing work.
A standard dormer conversion typically takes:
- 2–3 weeks for structural/roofing works (2 man team)
- 3–4 weeks for internal fit-out
- 1 week for second fix and finishing
At current UK rates, budget for £250–£400/day for a skilled tradesman depending on your region. Add 15–20% to your labour estimate to cover for rework, snagging, and unexpected structural finds.
Step 4: Add Your Overheads and Margin
This is the step most builders get wrong. Your quote needs to cover:
- Materials markup: Add 15–25% to your material costs to cover procurement time, wastage, and price fluctuations
- Overheads: Van, insurance, tools, phone — typically 8–12% of job revenue
- Net profit margin: Target 15–25% on residential works
If your combined material and labour cost on a dormer conversion comes to £28,000, you should be quoting at least £38,000–£42,000 to achieve a healthy margin.
Step 5: Present the Quote Professionally
A professional quote does two things: it wins the job, and it protects you legally. Your loft conversion quote should include:
- Itemised breakdown by trade/section
- Clear inclusions and exclusions (what's in the price and what isn't)
- Payment schedule tied to milestones
- Quote validity period (30 days recommended given material price volatility)
- Your company details and registration number
The Biggest Margin Killers on Loft Conversions
After talking to hundreds of UK builders, here are the most common reasons loft conversions eat into profit:
- Underestimating scaffolding duration — If the roofing phase runs over, you're paying weekly scaffold hire fees you didn't price for.
- Hidden structural issues — Always include a provisional sum for unknowns (typically £1,500–£2,500) and make sure your contract allows you to raise a variation.
- Material price changes — Timber and steel prices can shift 10–15% between quoting and ordering. Build in a materials clause or use live pricing tools.
- Scope creep from clients — Price every variation formally. "Can you just add..." conversations kill margins.
Use Software to Track Margin in Real Time
The best way to protect your margin isn't just quoting accurately — it's tracking actual costs against your estimate as the job progresses. If you're still using spreadsheets, you'll only find out you've lost money when it's too late to do anything about it.
QuoteBuild lets you build your loft conversion quote in minutes using UK trade price libraries, then track every material purchase and labour cost against your original estimate. You'll see your live margin on every job, and get alerted the moment a line item starts going over.
If you want the same quote-to-margin setup on your next loft job, see the full feature set or compare plans.
If lofts are part of your regular workload, see the builder page or browse all trade pages.