How Much Does a Loft Conversion Really Cost in London in 2026?

Real 2026 price ranges by conversion type, the hidden extras homeowners forget to budget for, and what actually moves your number up or down.

7 min read

If you've started pricing up a loft conversion, you've probably noticed the same thing we see with almost every client who calls us: the numbers online are all over the place. One website says £20,000. Another says £150,000. Neither is wrong — they're just talking about completely different projects.

The honest answer is that "how much does a loft conversion cost" doesn't have one number attached to it. It has a range, and where you land in that range depends on your roof shape, your borough, what you want the room to become, and how much you want it to feel like the rest of your house rather than an afterthought bolted on top of it.

We've put this guide together the way we'd talk you through it on a site visit — no inflated "from" prices designed to get you through the door, just realistic 2026 London figures and the factors that move them up or down.

01What Actually Determines the Cost?

Before we get into type-by-type pricing, it helps to understand what's really driving the number on your quote:

• The shape of your existing roof. A simple rooflight conversion barely touches the structure. A hip-to-gable job removes and rebuilds an entire end wall.
• Headroom. Ridge height close to 2.2m above the joists may allow a lighter-touch conversion; if not, you'll likely need a dormer or mansard.
• Planning route. Most rear dormers fall under permitted development — but conservation areas, Article 4 directions, and flats change this.
• What's going into the room. A bedroom with basic storage costs less than one with a bespoke en-suite and feature glazing.
• Your borough. Inner and prime London boroughs generally run 20–30% above outer London and the surrounding counties.
• Finish level. The structural shell is fairly consistent — it's flooring, decorating, and joinery that push the final bill.

02Loft Conversion Costs in London by Type

2026 price ranges, at a glance

Velux / Rooflight — the simplest and cheapest option, using your existing roofline with rooflights added for space and ventilation. Only suitable where headroom already allows it.

Dormer — the most common conversion in London, and usually our recommendation for terraced houses, creating a full-height room rather than a sloped attic space.

Hip-to-Gable — for semi-detached and detached houses with a hipped roof, converting the hip into a vertical gable wall for meaningfully more volume.

L-Shaped Dormer — common on Victorian and Edwardian terraces with a rear addition; usually enough for two bedrooms or a bedroom and proper en-suite.

Mansard — the most involved option, replacing the rear roof slope with a near-vertical wall. The standard approach in many conservation-area terraces where a dormer wouldn't be approved.

03Extras It's Easy to Forget to Budget For

• Structural engineer's calculations for Building Control (typically £400–£900)
• Party wall agreements and surveyor fees where you share a wall with a neighbour
• Planning application fees, if your project falls outside permitted development
• Skip hire and scaffolding permits, which vary by council
• Building Control inspection fees
• Flooring, decorating, and built-in storage — often the difference between a "finished shell" and a room that feels like the rest of your home

As a rule of thumb, we tell clients to add 10–15% on top of the headline construction figure to cover these — a far more useful number to plan around than a bare "from" price.

04What This Looks Like on a Real Project

A typical example we see regularly: a Victorian terrace in outer London with a hipped or standard pitched roof, converted into a double bedroom with a small en-suite via a rear dormer. Structural work, insulation, a new staircase, first fix, plastering, and second fix carpentry sit comfortably within the dormer range above, with the en-suite and finishing pushing the total toward the upper end. Projects like this typically run 6–10 weeks on site, and because the work is largely confined to the roof and one internal staircase run, most clients are able to stay living in the house throughout.

05Why Homeowners Choose Nemo Group UK

One point of contact, start to finish

A dedicated project manager coordinates design, structural work, and every trade in between, so you're never chasing three different contractors.

Fixed, transparent quotes

We price the full scope up front — structural work, staircase, insulation, plastering, and finishing — so there are no uncomfortable surprises halfway through.

We handle the paperwork

From permitted development checks to party wall notices and Building Control sign-off, we manage the process so you don't have to become a planning expert overnight.

In-house carpentry and decorating

Because our own teams handle the staircase, built-in storage, and final finish, your new room is styled and snagged to the same standard as the rest of your home.

Over 10 years building across London

We've converted lofts in terraces, semis, and period conservation-area properties across Greater London, Kent, Surrey, and Essex.

Ready to Get a Real Number for Your Loft?

Every roof is different, and the only way to get an accurate figure is a proper site visit. We'll assess your loft, talk through which conversion type suits your property, and give you a clear, itemised quote.

020 3576 6549

Frequently Asked Questions

Do I need planning permission for a loft conversion in London?+

Many loft conversions — particularly rear dormers within volume limits — fall under permitted development and don't need a full planning application. This changes in conservation areas, on flats, and under Article 4 directions, so it's always worth a proper check before you commit to a design.

How long does a loft conversion take?+

Most dormer and hip-to-gable conversions take 6–10 weeks on site once drawings and Building Control approval are in place. Mansard conversions and more complex projects can run longer.

Can I stay in my house during the work?+

Yes, in almost all cases. Because the work is largely contained to the roof space and a staircase opening, most of our clients continue living in the house throughout the build, with some noise and access disruption during the structural phase.

Does a loft conversion add value to my home?+

Yes — a well-executed loft conversion is consistently one of the best-value home improvements in London, both for the extra bedroom or living space it creates and for its impact on resale value. The exact uplift depends on your property, location, and specification.

What's included in a Nemo Group UK loft conversion quote?+

Our quotes cover structural work, steelwork, insulation, staircase, first and second fix, plastering, and decoration, priced as a fixed scope from the outset. En-suite bathrooms and bespoke joinery upgrades are scoped and priced separately.