Average Cost Loft Conversion – What You’ll Really Pay

Thinking about turning that dusty attic into a bedroom, office or playroom? The first thing most people ask is “how much will it cost?” In the UK a loft conversion typically runs between £20,000 and £45,000, but the final figure depends on a handful of key things.

What Drives the Price?

Size is the biggest factor. Most lofts add about 20‑30 square metres of floor space, and contractors charge roughly £1,200‑£1,800 per square metre. That means a 25 m² conversion could sit at £30,000‑£45,000 if you go for a full‑fit finish.

Structure also matters. If you need to reinforce joists, add dormer windows or install a new staircase, the labour and material costs jump. A simple “dormer‑lite” conversion might add £5,000‑£8,000, while a more complex design with a new roofline can push the total past £60,000.

Location plays a subtle role. Builders in London and the South East often quote higher rates than those in the North. Expect around 10‑15 % more if you’re working in a high‑cost area.

Breakdown of Typical Expenses

Design and planning: £500‑£1,500. If you need a structural engineer or planning permission, add another £1,000‑£2,000.

Staircase: £2,000‑£5,000 depending on style and material.

Insulation & flooring: £3,000‑£6,000. Good thermal insulation is a must for UK weather, and a decent floor finish adds comfort.

Windows & roofing: £4,000‑£10,000. Dormer windows are popular, but skylights can be cheaper.

Electrical & plumbing: £2,000‑£4,000. Adding sockets, lights and, if needed, a bathroom or en‑suite ups the cost.

Finishes: £5,000‑£12,000. This covers plasterboard, plastering, paint, doors and any built‑in storage.

Adding up these line items gives a realistic picture of where your money goes. Most homeowners end up spending around £30,000‑£40,000 for a well‑finished, comfortable loft.

If you’re on a tighter budget, look at where you can cut. A simple ladder access instead of a full staircase, standard double‑glazed windows, and basic flooring can shave a few thousand off the total.

Don’t forget hidden costs. You’ll need a building notice or planning permission for certain types of lofts, and a site survey might reveal roof repairs that need fixing before work can start. Budget an extra 5‑10 % for unexpected issues.

Choosing the right contractor can also affect price. Get at least three quotes, check references, and make sure the quote includes a detailed breakdown. A cheap quote might skip essential steps like proper insulation, which can cost you more in the long run.

Finally, think about resale value. A good loft conversion can add roughly 10‑15 % to your home’s market price, so the investment often pays off when you sell.

Bottom line: expect £20,000‑£45,000 for a standard conversion, £45,000‑£60,000 for a high‑spec build, and always add a contingency fund for surprises. With clear budgeting and the right builder, you can turn that empty space into a room you actually use.