Home Extensions vs Loft Conversions
Running out of space and weighing up building out with an extension versus building up with a loft conversion? Both add space and value, but they suit different needs, budgets and homes. Here's an honest, side-by-side comparison to help you choose.
The quick answer
Need more bedrooms? Building up with a loft conversion is usually the most cost-effective choice. Need more living, kitchen or dining space? Building out with an extension is normally the better fit.
Cost
Loft conversions are generally cheaper per square metre than rear extensions, because the roof and footprint already exist — there are no foundations or groundworks. Extensions cost more to start but can deliver larger, ground-floor open-plan space.
- Loft conversion: typically from around £25,000 (Velux/roof-light) to £45,000+ (dormer or hip-to-gable).
- Single-storey extension: typically from around £30,000 to £60,000+ depending on size and specification.
These are general guide ranges only — every project is different, so we provide a detailed, itemised quote after a site survey.
Added value
Both can add real value. A loft conversion that adds a genuine double bedroom (ideally with an en-suite) is one of the most dependable improvements, particularly where it increases the number of bedrooms. A large kitchen or living extension adds the open-plan family space many buyers prioritise. The strongest return depends on your home, your street and local demand.
Planning & regulations
Many loft conversions and single-storey rear extensions can be built under Permitted Development Rights without full planning permission — subject to limits on size, height and materials, and stricter rules for flats, listed buildings and conservation areas. Both require Building Regulations approval regardless of planning. We assess your property and handle any applications needed.
Disruption & timeline
Loft conversions tend to be less disruptive day-to-day, as most work is above your living space and access is often external via scaffolding — typically 4–8 weeks. Extensions involve groundworks and affect your garden and ground floor for longer — typically 3–6 months for a single-storey build, depending on scope.
Side-by-side
| Factor | Loft Conversion (build up) | Extension (build out) |
|---|---|---|
| Best for | Extra bedrooms / office | Kitchen, living, dining space |
| Typical cost | Lower (from ~£25k) | Higher (from ~£30k) |
| Garden space | Unaffected | Reduced |
| Disruption | Lower | Higher |
| Typical timeline | ~4–8 weeks | ~3–6 months |
| Planning | Often permitted development | Often permitted development |
Which should you choose?
Choose a loft conversion if you need bedrooms or a quiet home office, want to keep your garden, and want the most space for your money. Choose an extension if you want a bigger kitchen or open-plan living area on the ground floor and have the garden space to give up. And if budget allows, many homeowners do both — phased over time.
Not sure which is right?
We design and build both across Shrewsbury, Shropshire and the wider Midlands. Tell us what you're trying to achieve and your budget, and we'll advise honestly on the best option for your home — with a free, no-obligation quote.
Frequently Asked Questions
Which is cheaper — an extension or a loft conversion?
Loft conversions are usually cheaper per square metre because the roof structure and footprint already exist, with no groundworks or foundations. As a rough guide, a loft conversion often starts from around £25,000–£45,000 and a single-storey extension from around £30,000–£60,000+, but the final cost depends heavily on size, specification and your property. Always get a detailed, itemised quote.
Which adds more value to my home?
Both can add significant value when done well. A loft conversion that adds a double bedroom with an en-suite is one of the most reliable value-adds, especially where it increases the bedroom count. A large kitchen-diner extension adds sought-after living space and 'wow factor'. The best return depends on your property, area and what buyers there want.
Do I need planning permission for either?
Many loft conversions and single-storey rear extensions fall under Permitted Development Rights and don't need full planning permission — but there are limits on size, height and materials, and different rules for flats, listed buildings and conservation areas. Both still need Building Regulations approval. We assess your property and handle any applications required.
Which causes less disruption?
Loft conversions are generally less disruptive to day-to-day living because most of the work happens above your existing rooms and access can often be arranged externally via scaffolding. Extensions involve groundworks and can affect your garden and ground-floor rooms for longer. Either way, we plan the works to minimise disruption.
Can I do both?
Yes. Many homeowners phase the two — for example an extension now and a loft conversion later — to spread the cost and the disruption. We can help you plan a sensible order of works and design each phase so it complements the other.