Dormer Attic conversion versus Single Storey Extension

Here’s an illustrative image showing a “Dormer roof lift” transformation—raising the roof ridge to create full-height living space upstairs. Great to see how it enables a complete second-floor layout.

Let’s dive into the advantages and drawbacks of a residential roof lift (i.e., raising the roof to gain floorspace) versus a single-storey house extension in the UK.

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DormervRoof Lift (Raised Roof Loft Conversion)

Pros

• Maximises living space without sacrificing garden area

Ideal if your outdoor space is limited—it expands upward rather than outward .

• Creates full-height rooms across most of the upstairs area

Unlike typical loft/attic conversions, a dormer roof lift provides headroom throughout, ideal for bedrooms, bathrooms, or living areas .

• Significant boost to property value—potentially up to 25–30%

Especially in bungalows converting into two-storey homes .

• Stronger and refreshed roof structure

The old roof is replaced, improving structure and insulation, and removing obstructive beams .

• You can remain living in the property during works

Existing ceilings stay intact, and disruptions can be minimised .

Cons

• Can sometimes require full planning permission

Since it can alter the home’s external profile and ridge height .

• Costly

Typically costs between £35,000–£75,000, averaging around £55,000; bungalow conversions can go as high as £60,000 .

• Technically complex and time-consuming

Will require architectural and structural input, crane access, scaffolding, and longer planning/build times—build takes around 6–8 weeks, with full timelines up to 10–12 weeks .

• Structural constraints and suitability

Not all roof types (e.g., those with trusses) are workable; requires structural surveys, and some property types (like terraced homes) will need a party wall agreement .

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Single-Storey Extension

Pros

• More affordable and easier to fund

Generally less costly than adding a whole new loft conversion floor, offering good value for functional ground-floor space .

• Permitted development rights often apply

Many single-storey rear extensions can be built without planning permission, following size, height, and design limits (under 4 m height, up to 6 m extension depth on a semi and 8 m on a detached) .

• Faster build times

Typical timeframe is 2–4 months, shorter than multi-storey work .

• Less disruptive

You may be able to continue living at home with minimal impact, as work is confined to ground floor .

Cons

• Reduces outdoor/garden space

Extending outwards eats into your garden—less ideal if outdoor space matters greatly .

• Limited to single-floor space

You can’t add upstairs bedrooms or lofts—space stays on the ground floor.

• Potential planning limitations in some areas

Despite permitted development, extensions exceeding size limits or in restricted areas (like conservation zones) may require full permission .

• Roof type affects cost and aesthetics

Flat roofs are cheaper (e.g. ~£52,500) but less durable, need more maintenance, and have shorter lifespan. Pitched roofs cost more (£60,000+), but last longer and suit traditional styles better .

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Quick Comparison Table

Feature Roof Lift Single-Storey Extension

Space Added Full second floor—bedrooms, etc. Ground-floor only

Garden Impact None Reduced due to footprint

Cost Estimate £35k–£75k (avg ~£55k) Varies—but typically less

Planning Permission Required Often PD rights apply

Build Time ~10–12 weeks total (6–8 weeks build) ~2–4 months

Disruption Moderate (roof works, scaffolding) Relatively low (confined area)

Added Property Value High potential (25–30% uplift) Good, but less transformative

Aesthetic/Structural Major external change Ground-level change, often seamless

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Which Option Suits You Best?

• Go for a roof lift if you need significant upstairs space (e.g., bedrooms or bathrooms), want to boost value, have limited garden, and are prepared for higher cost and complexity.

• Choose a single-storey extension if you just need more ground-level space, want to keep costs lower, have a good-sized garden, and want a quicker, simpler planning process.

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Remember that whether you want a dormer rooflft or a single storey extension (which may or may not require planning permission). You will always be required to obtain building regulation approval.

Building regulations requires the uk building specifications to be specified along with any structural items so as obtain this approval.

Note that planning permission (if required), and building regs permission are separate requirements that you need before you can build anything in the UK.

Contact Chris at Homeplan Designs and let him know your property specifics and what type of additional space you need—we are happy to help you decide which route fits best for your situation!