Hip to Gable vs Dormer Conversion

So you're thinking about a loft conversion. Good for you. But now you're stuck between two options: hip to gable or dormer. And honestly, it's not always obvious which one's right. They both give you more space, sure. But the way they work, what they cost, and what you'll need to get permission for? Totally different beasts. Let's break it down.

What is the main difference between a hip to gable and a dormer conversion?

Think of it this way. A hip to gable conversion actually changes the shape of your roof. You've got that sloping hip roof, right? Well, you're basically chopping off the slope and putting up a flat wall instead. More room inside. A dormer? That's like sticking a box onto your existing roof. It pops out, gives you headroom where you didn't have any. But the main roof stays put.

So the real difference is approach. Hip to gable expands the roof volume by reshaping it. Dormer adds something new onto it. Here's the catch though: hip to gable only works on semi-detached or detached houses with a hipped roof. Dormers? They're pretty flexible. Most roof types can handle them.

How much does a hip to gable conversion cost compared to a dormer?

Let's talk money. Because that's what everyone really wants to know. Generally, hip to gable will cost you more. All that structural work, the steel, the scaffolding... it adds up. Here's a rough idea for UK prices in 2025.

Those numbers include the planning fees, steelwork, insulation, and basic finishes. Hip to gable needs more heavy work - more steel, bigger scaffolding. That's why it's pricier. Dormers are cheaper but you might run into more complicated roofing details to keep the weather out.

Which conversion type is better for adding value to my home?

Both will bump up your property value. But how much? Hip to gable tends to win here. You get a bigger room, it looks more natural. Especially on semi-detached houses where the gable end can match the neighbour's. Buyers like that.

Dormers add value too, don't get me wrong. They give you headroom and you can design them to look decent. A good dormer can turn a dusty attic into a proper bedroom or office. But sometimes they look a bit... tacked on. Not always seamless.

Honestly, if you're after max return on investment, hip to gable is probably your bet. Especially in areas where big loft spaces are hot. But if you're on a tighter budget, a dormer is a solid way to add value without breaking the bank.

Do I need planning permission for a hip to gable or dormer conversion?

Here's where it gets tricky. In the UK, a lot of dormer conversions fall under permitted development. So no planning permission needed - as long as you follow the rules. Don't go higher than the existing roof, don't face a highway, that sort of thing. Hip to gable though? Almost always needs full planning permission. You're changing the roof shape, after all.

Key things to remember:

• Hip to gable conversions: You'll need a full planning application. Can't go above the ridge height. And forget it if you're in a conservation area.
• Dormer conversions: Might be permitted development if you stay within volume limits (40 cubic metres for terraced, 50 for detached/semi-detached). And again, don't go higher than the ridge.
• Both: Building regulations approval is a must. Structural safety, fire escape, insulation - non-negotiable.

Seriously, talk to a local planning officer or an architect before you do anything. Local rules can be a minefield.

What are the pros and cons of each conversion type?

Alright, let's weigh it up. No sugarcoating.

Hip to Gable Conversion Pros

• You get a bigger, more open space. No awkward corners.
• Looks better from the outside. Adds kerb appeal.
• Usually adds more value than a dormer.
• You can combine it with a rear dormer if you're feeling ambitious.

Hip to Gable Conversion Cons

• It's expensive. And it takes longer.
• Planning permission is almost always needed.
• Only works on hipped roofs. Sorry.
• Might need party wall agreements if you're semi-detached.

Dormer Conversion Pros

• Cheaper. Faster. Gets you space quicker.
• Often no planning permission needed.
• Works on most roof types.
• Great for headroom and natural light.

Dormer Conversion Cons

• Can look ugly if not designed well. Really obvious.
• Might eat into your garden or side space.
• Less internal floor space than hip to gable.
• Risk of water leaks if the flashing isn't done properly.

Frequently Asked Questions