What are the four types of loft conversion?

Thinking about adding some space and bumping up your home's value? A loft conversion is honestly one of the best moves you can make. But here's the thing—lofts aren't all the same. What you can actually build depends on your house, your wallet, and those local planning rules nobody loves dealing with. Knowing the four main options? That's how you pick the right one.

So, the big four are: Velux (roof window), Dormer, Hip-to-Gable, and Mansard. Each one gives you a different mix of cost, space, and how much of a headache it is. Let's get into it.

1. What is a Velux or roof window loft conversion?

This is the simplest one, and honestly, the cheapest. You're basically cutting holes in your existing roof and sticking windows in—no changing the roof shape. They reinforce the floor, add a staircase, and that's pretty much it. The roof line stays exactly as it is.

• Best for: Homes where you've already got decent roof space and a slope that's steep enough.
• Pros: Barely any structural stuff, fast to finish, and usually you don't need planning permission (permitted development covers it).
• Cons: You're stuck with whatever headroom and floor space you've got—the room follows the roof slope.
• Average cost: £20,000 – £35,000
• Time to complete: 4–6 weeks

2. What is a dormer loft conversion?

This is the one everyone talks about. You're pushing the roof outward—vertically—to make this box-like thing with a flat roof and straight walls. Boom, instant headroom and way more usable floor space.

• Best for: Houses with a pitched roof where you need room to stand up and a bigger room.
• Pros: Most extra headroom you can get, flexible layout, and often still under permitted development.
• Cons: Costs more than Velux, needs structural changes, and it'll change how your house looks from the outside.
• Average cost: £35,000 – £55,000
• Time to complete: 6–8 weeks

Dormer types explained

Not all dormers are the same. You've got flat roof dormers (most common), pitched roof ones (blends in nicer), and shed dormers with a sloped roof—often used for bathrooms.

3. What is a hip-to-gable loft conversion?

This one's for homes with a hipped roof—where it slopes on all sides. What happens is you replace that sloping side (the hip) with a straight vertical wall (a gable). So your roof goes from hipped to gable-ended, and you get a much bigger, more rectangular floor area.

• Best for: Detached, semi-detached, or bungalows with a hipped roof on one side.
• Pros: Way more internal floor space and headroom than a simple dormer.
• Cons: Usually needs planning permission, more complex structurally, and can get pricey if the roof needs big changes.
• Average cost: £40,000 – £65,000
• Time to complete: 8–10 weeks

4. What is a mansard loft conversion?

This is the big one—the most dramatic and expensive. You're basically rebuilding the entire roof. It gets a near-vertical slope (about 72 degrees) and a flat top. The result? A whole new floor with walls that are almost straight, squeezing every square metre out of the space.

• Best for: Period properties, terraced houses, and anyone who absolutely needs max space.
• Pros: You get a full, livable floor with near-vertical walls and loads of headroom.
• Cons: Crazy expensive, needs full planning permission, super disruptive, and takes months.
• Average cost: £55,000 – £80,000+
• Time to complete: 10–16 weeks

Comparison table of loft conversion types

People also ask about loft conversions

Do I need planning permission for a loft conversion?

Most of the time, loft conversions fall under permitted development rights, so no formal application needed. But that depends on your house type, how much you're adding, and whether you're in a conservation area or a listed building. Dormer and Velux often qualify, but hip-to-gable and mansard? Yeah, you'll almost always need full permission. Always check with your local planning authority before you start.

Which loft conversion adds the most value?

All of them add value, no doubt. But mansard conversions usually give you the best return because you're creating a full floor with max headroom. Dormers also add plenty—often getting back 70-80% of what you spent. Velux adds value too, but less because you're not gaining as much space.

How long does a loft conversion take?

Depends on the type. Velux? 4-6 weeks. Dormer? 6-8. Hip-to-gable? 8-10. Mansard? 10-16 weeks or longer. Weather, structural complexity, and when your contractor's free all play a part.

Frequently asked questions

Note: Costs and timelines are approximate and can vary significantly based on location, property size, and contractor rates. Always obtain multiple quotes and consult a professional.