Loft Conversion Types Explained: Which Is Right for Your UK Home?

A loft conversion is one of the smartest ways to add space and value to a UK home — no garden land lost, often no planning permission needed, and a typical return on investment of 15–20%. But not all loft conversions are equal. The right type depends on your roof structure, property type, budget, and what you want the space for.

Here's a practical comparison of the four main types to help you decide.

1. Velux (Rooflight) Conversion

Best for: Properties with good existing head height

The simplest and cheapest option. A Velux conversion works within the existing roof shape — no structural changes to the roofline. Roof windows (Velux is the brand name, but it's become the generic term) are installed to bring in light and ventilation.

What's involved:

• Strengthening the floor joists
• Adding insulation between and over the rafters
• Installing roof windows
• Building a staircase
• First-fix electrics and plumbing (if adding an en-suite)
• Plastering, decorating, and flooring

Typical cost: £20,000–£35,000

Pros: Cheapest option, fastest build (4–6 weeks), almost always falls under permitted development

Cons: Limited by existing head height, less usable floor area than a dormer, no additional external volume

Works best with: Victorian and Edwardian homes with steep pitched roofs, detached houses with tall ridge heights

2. Rear Dormer Conversion

Best for: Most UK homes, especially semis and terraces

The most popular type of loft conversion in the UK. A dormer is a box-shaped structure that projects out from the rear roof slope, creating a flat-ceilinged room with significantly more usable floor area than a Velux conversion.

What's involved:

• Removing the rear roof slope (partially or fully)
• Building the dormer structure with a flat or slightly pitched roof
• Structural steel to support the new opening
• Everything listed under Velux, plus the dormer construction

Typical cost: £35,000–£55,000 (£45,000–£70,000 in London)

Pros: Maximum usable space, works on most property types, usually permitted development (rear only)

Cons: More expensive than Velux, 6–8 week build time, needs careful design to look proportionate

Works best with: Semi-detached and terraced homes where head height is limited, any property where you want a full-height bedroom with en-suite

3. Hip-to-Gable Conversion

Best for: Semi-detached and detached homes with a hipped roof

If your roof slopes inward on one or both sides (a hipped roof), you're losing significant loft space. A hip-to-gable conversion extends the sloping side wall vertically to create a full gable end, then typically adds a rear dormer for maximum space.

What's involved:

• Removing the hipped roof section on one side
• Building a new gable wall to the full height of the ridge
• Structural steelwork to support the new configuration
• Usually combined with a rear dormer

Typical cost: £40,000–£65,000 (hip-to-gable + rear dormer)

Pros: Transforms otherwise unusable loft space, dramatic increase in floor area, high ROI

Cons: More structural work required, may need planning permission in some areas, not suitable for terraced homes (no side wall to extend)

Works best with: 1930s–1960s semis with hipped roofs — one of the most common UK house types

4. Mansard Conversion

Best for: Maximum space, high-value properties, townhouses

A mansard conversion replaces one or both roof slopes with a near-vertical wall (typically 72 degrees) topped by a flat roof. This creates the most internal space of any loft conversion type — essentially a full additional storey.

What's involved:

• Removing most or all of the existing roof structure
• Building new mansard walls with windows
• New flat roof with drainage
• Extensive structural steelwork
• Full scaffolding for the duration

Typical cost: £55,000–£80,000+ (£70,000–£100,000+ in London)

Pros: Maximum floor area and head height, can transform a property, works on properties where other types don't

Cons: Most expensive option, almost always requires planning permission (changes the roofline), longest build (8–12 weeks), significant scaffolding

Works best with: Terraced townhouses, properties in high-value areas where maximising space justifies the cost, listed buildings (with consent) where a sympathetic mansard may be the only option

Choosing the Right Type

| Property Type | Recommended Conversion | |---|---| | Victorian/Edwardian terrace (steep roof) | Rear dormer or Velux | | 1930s semi (hipped roof) | Hip-to-gable + rear dormer | | Detached (good head height) | Velux (budget) or rear dormer | | Terraced townhouse | Mansard or rear dormer | | Bungalow | Rear dormer or mansard | | Modern home (trussed roof) | Rear dormer (with truss removal) |

Key Decisions Before You Start

1. Check your head height. Measure from the top of the ceiling joists to the underside of the ridge. Under 2.2m? You'll likely need a dormer or mansard.

2. Check your roof structure. Traditional cut timber roofs are straightforward. Modern trussed roofs need more structural work — budget an extra £5,000–£10,000.

3. Think about the staircase. The staircase location affects the room below. It typically takes space from an existing bedroom or landing. Plan this early.

4. Consider an en-suite. Adding a shower room or bathroom to a loft conversion costs £3,000–£6,000 extra but significantly boosts both usability and resale value.

5. Get a personalised quote. Costs vary hugely by region, roof type, and specification. Use our free loft conversion quote calculator for an itemised estimate, or browse loft conversion costs by city to see typical prices in your area.

Building Regulations Essentials

Regardless of whether you need planning permission, every loft conversion must comply with Building Regulations:

• Structural safety — floor, walls, and roof must be properly engineered
• Fire safety — protected escape route, fire doors, and smoke alarms
• Insulation — must meet current thermal performance standards
• Staircase — minimum width, headroom, and pitch requirements
• Sound insulation — between the loft room and rooms below

Never skip Building Regulations approval. Without a completion certificate, you'll face serious problems when selling your home.