Loft Conversion Types
Dormer Loft Conversions
A box built out from the back of the roof, turning a sloping ceiling into a flat one. It's the conversion most people picture, and the one most West London houses end up with.
What a Dormer Conversion Does
The problem with almost every unconverted loft is the same: the ceiling slopes, so the only place you can stand up straight is a narrow band under the ridge. Everything else is storage height.
A dormer fixes that by building a structure out from the rear roof slope with vertical walls and a flat roof. Where the slope was, you get full standing height, a flat ceiling and a proper window. The floor area barely changes — what changes is how much of it you can use.
It is by a distance the most common loft conversion in West London, for two reasons. It works on almost any house with a pitched roof, terrace or semi. And because it sits at the back, it's frequently permitted development, which takes the longest and least predictable part of the process off the table.
Rear Dormer, Full-Width, or Something Else?
A Rear Dormer
Sits within the rear roof slope with roof left either side. It's the least visually intrusive version and the easiest to get through planning if planning is needed at all.
A Full-Width Dormer
Runs the entire width of the rear roof. You get the most floor area at full height, and it's usually what makes a bedroom-plus-bathroom layout work. It's also the version most likely to draw comment from a planning officer.
A Front Dormer
A different conversation. Roof extensions cannot go beyond the plane of the roof slope that fronts a highway under permitted development, so a front dormer means a planning application almost by definition.
If Your Roof Is Hipped at the Side
A dormer alone leaves the width problem unsolved. Look at a hip to gable, usually combined with a dormer.
What the Work Involves
Opening the Roof
The rear slope is stripped back and the dormer structure framed out — vertical front, flat roof, sides either tiled or clad.
Structure
Steel or timber to carry the new floor and support the roof around the opening. The existing ceiling joists are almost never strong enough to be a floor.
The Stairs
A permanent staircase with at least 2 metres of headroom over the whole flight and landings. On a narrow terrace this is often the hardest part of the design, not the roof.
Fire Safety
Escape windows aren't accepted in a two-storey house, so the existing stairway becomes the protected escape route: fire doors onto the stairs, a 30-minute fire-resisting floor, interlinked mains-powered smoke alarms at every level.
Weathering and Finish
Roof covering, flashing, guttering, insulation, plasterboard, decoration.
Most rear dormers in West London are finished with tile-hung or clad sides so they read as part of the roof rather than a bolted-on box. On a street where several houses have already converted, matching what's there is usually the shortest route to a straightforward planning conversation.
What a Dormer Costs
| Scope | Typical West London range |
|---|---|
| Rear dormer | £42,000 – £62,000 |
| Full-width rear dormer | £48,000 – £68,000 |
| Add an en-suite | £5,000 – £9,000 |
These are estimates for West London, not quotes. What your loft actually costs depends on your roof, your access and what you put in the room — which is exactly what a survey is for.
The main variables are width, whether a bathroom goes in, and access. A terrace with no side access means every skip, every steel and every tile goes through the house, and that shows up in the price.
Is a Dormer Permitted Development?
Frequently, yes — a rear dormer is one of the more reliable permitted development projects, provided it stays inside the limits.
The volume allowance is 40 cubic metres for a terrace house and 50 cubic metres for a semi-detached or detached house, measured against the original roof space. A full-width dormer on a wide house can eat into that faster than people expect, so it's worth calculating early.
Permitted development also requires that no part goes above the highest point of the existing roof, that the materials are similar in appearance to the house, that the eaves are kept and the addition set back at least 0.2 metres from them, and that any side-facing window is obscure-glazed and non-opening below 1.7 metres from the floor. Balconies, verandas and raised platforms are excluded outright.
Conservation areas are the exception. Roof enlargements are not permitted development on designated land, which includes conservation areas. Ealing has 30 of them, and six carry Article 4 directions that remove householder rights further. If you're in one, this conversion needs full planning permission — which doesn't mean refusal, just an application.
Building regulations approval is required either way. It's a separate consent from planning and it applies even when no planning permission is needed at all.
Dormer Conversions Across West London
Rear dormers get built everywhere in this part of London, but they're the default answer in these areas:
Dormer Questions
How much extra space does a dormer actually add?
Very little floor area, and a great deal of usable floor area. On a typical terrace you'd go from a couple of square metres you can stand in to most of the room.
Will a dormer look out of place?
From the street, usually not — a rear dormer isn't visible from the front. From the garden and from neighbours' upper windows it is, which is why cladding and proportions get attention in the design.
Can I have a balcony on it?
Not under permitted development. Balconies, verandas and raised platforms are specifically excluded, so a Juliet-style opening or a full application are the routes.