Types of Dormer: The 8 Dormer Styles on UK Homes, Explained with Diagrams

Before we go into each one, here is the whole family in a single picture. Each sketch shows the same roof with a different dormer shape highlighted, so the differences read instantly.

The quickest way to sort them is by roof shape. Flat roof, shed and full-width dormers give you the most usable floor area and go on the rear of everyday houses. Gable, hipped and eyebrow dormers are the smaller, prettier ones that suit period homes and conservation streets where a big box would look wrong. Wall dormers are the odd one out, a Georgian and contemporary detail that starts from the wall below. The L-shaped dormer is a layout rather than a shape, two dormers joined at a right angle to squeeze the most space out of a Victorian terrace.

This page is the informational companion to our full dormer loft conversion service page, which covers the transactional detail, quotes and the five dormer conversions we build most often. If you want to compare a dormer against a Velux, hip-to-gable or mansard, start with the loft conversion types guide instead.

Every dormer, whatever its shape, is built from the same handful of parts. Knowing the names makes the rest of this guide, and any conversation with a builder or planning officer, much easier to follow.

• Face: the front wall of the dormer, usually holding the main window. This is the part you see and the part a planning officer judges hardest.
• Cheeks: the two vertical side walls that connect the face back to the roof slope. Cheeks are commonly clad in lead, zinc, slate or tile to match the house.
• Roof: the top of the dormer. On a box dormer it is flat with a slight fall for drainage; on a gable or hipped dormer it is pitched.
• Flashing: the weathered joint, in lead or zinc, where the dormer meets the main roof. Poor flashing is the single most common cause of dormer leaks, so it is worth getting right.
• Window: in the face, and sometimes in the cheeks. Side windows in the cheeks have to be obscure-glazed under permitted development rules.
• Eaves and ridge: the eaves are where the roof meets the wall at the bottom, the ridge is the highest point at the top. A permitted development dormer has to sit below the ridge and stay set back from the eaves.

Behind the finish sits the structure. Smaller dormers use a timber portal frame, and larger box dormers over about three metres wide use a steel goal-post frame designed by a structural engineer. Either way the roof slope is cut open, new timbers or steels carry the load, and the box is framed, insulated to current Part L standards, weatherproofed and finished.

These three are the volume producers. If your goal is a full master bedroom with an en-suite rather than a pretty roof feature, one of these is almost certainly what you want.

Flat roof box dormer

The flat roof box dormer is the everyday UK dormer, and it accounts for more conversions than every other type put together. It is a simple box with vertical cheeks, a vertical face and a flat roof laid to a shallow fall. Because the walls are vertical and the roof is flat, it gives the maximum internal headroom and floor area for the money.

It suits Victorian and Edwardian terraces, 1930s semis, modern townhouses and most standard pitched-roof houses. On the rear slope it usually falls within permitted development, which is a big part of why it is the default choice. In Heaton and Jesmond, the flat roof rear dormer is the standard answer on the Tyneside terraces, where the roofs line up neatly for one. The trade-off is looks. A poorly proportioned box can dominate the rear elevation, so the design has to be kept in scale. Rough 2026 cost is £35,000 to £60,000 fitted across most of the UK.

Shed dormer

A shed dormer looks similar to a flat roof dormer but has a single pitched roof sloping in the same direction as the main roof, only shallower. That slope sheds rainwater better than a truly flat top and reads as softer against a steep roof. It gives generous headroom across a wide area and blends into both modern and traditional homes. Shed dormers are often folded into mansard extensions to keep the overall composition tidy. Cost sits close to a flat roof box, roughly £35,000 to £60,000 depending on width and finish.

Full-width box dormer

A full-width box dormer runs the entire width of the rear roof slope, from one party wall to the other. It delivers the most floor area from a single dormer, often enough for two bedrooms or a large master suite with a dressing area. The catch is appearance and planning. A full-width box looks visually heavy from the rear and is more likely to catch a planning officer's eye. On a terrace the 40 cubic metre volume cap is the binding constraint and a deep full-width dormer can breach it. On a semi or detached house you have the larger 50 cubic metre allowance to work with. Cost runs £45,000 to £75,000 nationally, more in London.

These are the dormers you choose when appearance matters as much as space, on period homes, cottages and conservation streets where a big rear box would look out of place. They usually form individual dormer windows rather than one wide roof addition.

Gable-fronted (dog-house) dormer

A gable-fronted dormer, also called a gabled or dog-house dormer, is the classic traditional shape. It has a dual-pitched roof of two sloping planes meeting at a central ridge, with a flat triangular gable end facing forward. It mirrors the look of a small house roof, which is why it sits so comfortably on Victorian and Edwardian properties. It drains and weathers well and is often the version most likely to win consent in a conservation area. The pitched roof eats into headroom compared with a box, so you gain character at the cost of a little usable space. This is the shape you see on the older terraces around Tynemouth and the period streets of Jesmond.

Hipped dormer

A hipped dormer is like a gable dormer but with a front sloping section too, so it has three sloping planes rising to a single ridge, echoing a hipped main roof. The geometry is a little harder to build and needs guttering on all three sides, which nudges the cost up. It is the right pick when you are matching an existing hipped roof or a run of hipped dormers on a detached or semi-detached home, and it gives a soft, refined silhouette. Because the front slope trims headroom further, a hipped dormer offers the least internal space of the character group.

Eyebrow dormer

An eyebrow dormer is the most distinctive of all. It is a low, wide dormer with a gently curved roof and no cheeks at all, the roof covering flowing up and over the window in a flattened bell curve, like an eyebrow. It adds light and a graceful architectural note without adding much headroom, so it is chosen for looks rather than usable space. Eyebrow dormers suit heritage properties, cottages and character homes, and they need precise waterproofing because of the continuous curve. Do not plan a bedroom around one, plan it around light and kerb appeal.

The last two do not fit the earlier groups. One is a distinctive architectural form, the other a clever layout for a specific house type.

Wall dormer

A wall dormer, sometimes called a lucarne, is a dormer whose face is flush with the wall below rather than set back up the roof slope. It breaks through the eaves line and reads as a continuation of the wall carried up above the roof edge. It is a common feature in Georgian domestic architecture, where the roof forms part of the upper storey, and it turns up in contemporary homes that borrow traditional forms. Because it breaks the eaves line, a wall dormer almost never qualifies as permitted development, so plan for a full planning application from the outset.

L-shaped dormer

An L-shaped dormer is not a single shape but two dormers joined at a right angle, one over the main rear roof and a smaller one over the rear outrigger or back addition. Seen from above the pair forms an L. It is the classic solution for Victorian and Edwardian terraces that have that long thin two-storey rear wing, the kind of Tyneside terrace with a back-addition kitchen below. It produces one of the most generous loft floorplans you can get on a period terrace, often two bedrooms plus a bathroom, sometimes three rooms on a wide plot. The trade-offs are complexity and planning. The extra leg of the L frequently pushes the combined volume past the 40 cubic metre terrace cap, so many L-shapes need a full planning application. Cost runs £45,000 to £65,000 nationally, higher in London. If you live in a Victorian terrace in Heaton or Jesmond, the L-shape is usually the version that gives you the most house for the money. See our dormer loft conversion service page for the full cost build-up.

A note on piggyback and recessed dormers

Two related terms come up often. A piggyback is a small secondary extension built onto an existing dormer to grab a bit more headroom or space, typically £15,000 to £40,000. A recessed dormer is set back into the roof rather than projecting out, trading floor area for a more discreet appearance and an easier ride in sensitive streets. Neither is a primary dormer shape, but both are worth knowing if you already have a conversion and want more.

The obvious dormer for your home is decided mostly by your roof shape, then filtered by what the council will allow. This table maps the common UK housing stock to the dormer that usually fits best, with a rough 2026 cost band.

For a bungalow specifically, the choice between a modest dormer and a full roof rework is a bigger decision, so see our bungalow loft conversion guide. If your roof is hipped, the hip-to-gable loft conversion page explains how squaring off the hip pairs with a rear dormer. And if you are weighing a dormer against rebuilding the whole roof, compare it with the mansard loft conversion.

Most rear dormers on houses in England are permitted development and do not need a planning application. They fall under Class B of Part 1, Schedule 2 of the Town and Country Planning (General Permitted Development) Order 2015, as amended. The single most important rule is the added roof volume cap.

To stay within permitted development, all of the following have to be true:

• Added roof volume stays under 40 cubic metres for a terraced house or 50 cubic metres for a semi-detached or detached house, counting every past roof addition since 1948, not just the new dormer.
• The dormer does not sit above the highest point of the existing roof ridge.
• The dormer is set back at least 20cm from the original eaves.
• Materials are similar in appearance to the existing house.
• No verandas, balconies or raised platforms.
• Any window in a cheek facing a side boundary is obscure-glazed and non-opening below 1.7m from the floor.

Front dormers almost always need permission

This is the rule that catches people out. A dormer on the principal elevation, the roof slope facing the highway, is never permitted development. A front-facing dormer always needs a full planning application, and councils are cautious about them because they change the street scene. A common workaround is a permitted development rear dormer for the space, plus rooflights on the front for light.

Conservation areas and listed buildings

In a conservation area, Area of Outstanding Natural Beauty, National Park or World Heritage Site, the Class B right is removed entirely, so even a modest rear dormer needs planning permission. Listed buildings need Listed Building Consent on top. An Article 4 direction can remove permitted development rights on a specific street, which is common in areas of uniform character, so check with your council before you design.

Fees and certificates

A householder planning application in England costs £548 from 1 April 2026. If your dormer is permitted development, it is still worth applying for a Lawful Development Certificate, which costs £274 for proposed works and gives you a formal document a buyer's solicitor will ask for when you sell. Whatever the planning route, Building Regulations approval is required for every dormer without exception, covering structure, fire escape, insulation and the new staircase. Read the full detail on our loft conversion planning permission and loft conversion building regulations pages.

Cost tracks the shape. The character dormers are smaller and cheaper, the box and full-width dormers cost more but deliver far more usable space. These are realistic fitted, mid-spec figures for the UK in 2026, and the North East (Newcastle, Gateshead, Sunderland) typically runs around 12 percent below the national average.

These cover the build. Architectural drawings, the structural engineer, Building Control fees and final bathroom fixtures usually sit on top, unless a firm quotes a single fixed price. What pushes a number up is the same across every type: steel sizes, party wall surveyors on terraces and semis, en-suite plumbing routes, high-end finishes and hard access for materials. For the full line-by-line breakdown see our loft conversion cost guide, and for how the build actually runs week by week see how to convert a loft. Every project we deliver comes with a free home survey, a fixed-price written quote in 5 working days, no deposit until work starts, and a 10-year insurance-backed structural guarantee.