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  • Writer's pictureLouise Jones

Garden Rooms vs Extensions – What’s Best?

There is no structural reason that anything you do in a brick-and-mortar home can’t be done in a well-built garden room.

Annual data from the price comparison site Reallymoving shows the average cost of moving is now more than £14,000. You’ll need to pay upfront fees, stamp duty and legal expenses. There are also costs closer to your moving date, including removal vans, packing materials and cleaning. Plus, many homeowners love their home, its location, the family is settled at work, in school; so many people choose to extend their home rather than move.

Some of the most popular ways to extend your home include building a conservatory, a loft conversion, garage conversion, an extension or garden room. Here we’ll weigh up the advantages and disadvantages of building a garden room vs home extension.

We all know what an extension or conservatory is but what exactly is a garden room?

A garden room is a building that is detached from the main home in your garden but is built to high standards; this includes full insulation, electricity, lighting, windows, doors etc. that provides a fully insulated comfortable living space that can be used all year round; it is not a summer house or posh shed.

The first thing to decide is what do you need extra space for?

If you are looking for a quiet area away from the distractions of the main home, a garden room could be the perfect solution; an office or work space, a room for the kids, an artist studio, somewhere to operate your business from, a gym, a music room, a games room. The beauty of garden rooms is that they are extremely versatile, flexible spaces. If you are looking for a larger kitchen or more bedrooms and bathrooms a built extension is likely to be a better option.

Home Extensions vs Garden Rooms

Cosy Garden Rooms

Traditional Single-Story Extension

£/m² Fully Finished

£1100 - £1500

£1800 - £30001

20m² Size Example Cost

£25000 - £30000

£40000 - £560001

From Decision to Completion

1 - 2 months

7 - 15 months4 

Time on Site

3 - 6 days

2 - 4 months4 

Design Drawings Cost


£350 - £9501

Project Management


15% - 25% of Project Cost1

Planning Permission

Rare for Outbuildings

Only if within PDR2

Building Regs Sign Off

No, up to 30m² internal area

Yes - can cost extra

Add Value to your Property

Yes - Average 8.4%3 

Yes: 10% - 20%1

Disruption to the Main House



A cedar clad garden room with covered side area and large patio doors.

Planning Permission

The majority of house extensions will need planning permission, this is not the case with garden room; 90% fall within permitted development guidelines. This makes the garden room build faster, without delays or uncertainties that the planning application process can incur. The average planning application takes 8 weeks for minor works and double this for larger projects.

At Cosy Garden Rooms, your bespoke garden room can be built and ready for use within 4 - 6 weeks from initial enquiry.


A garden room can often be a more cost-effective solution to the problem of increasing available space in your home. On average, the cost of a house extension in the UK can range from £1,800 to £3,000 per square metre.  An average extension of 30m² is estimated between £54,000 to £90,000. In comparison an insulated garden building would cost around £35,000 and a basic building as low as £15,000.

Adding value to your home

A home extension essentially adds extra room/s to your property which can increase its sale value significantly, especially if you build a two-story extension that encompasses an extra bedroom and reception room.

Garden rooms also add value to your property? Recent data from the Land Registry paints a compelling picture: the average price paid for a house in the UK stands at £312,415. By incorporating a garden room into the property, homeowners could potentially see the value increase by up to £15,600 based on a basic garden room with average costs.

A garden room is also often a sought-after feature for homebuyers who are looking for a dedicated office space or games room.

Connection to nature

A garden room is a happy medium between spending time in your home and in your garden. A garden room feels intrinsically linked to your garden and the outdoors. It feels much different to an extension.

Bi fold doors, corner windows, picture windows, patio doors, in your garden room makes you feel like you are surrounded by your garden and can provide you with a real sense of tranquillity and peace. Spending time in a bright and airy space away from your home is a great way of feeling like you’re getting away from things for a while and you’re spending time outside, despite being in a garden building.

Construction and timescales

When starting an extension project, it is important to be realistic about timescales and costs. Things often take longer than you think and cost more than you expect. On average, a single-story extension takes around 3-4 months to complete (once planning approval has been granted) this can vary depending on the size of your build.

Depending on the amount of ground works, size and specification of your garden room a Cosy Garden Room takes between 3 – 6 days to build. Cosy Garden Rooms offer a complete service and can remove old buildings if required. We can also incorporate kitchenettes, toilets and showers. This may take a little longer.

Disruption and mess

Extensions involve demolition, brickwork, dust, lots of dust and noise and possibly requiring temporary relocation for the family. Garden rooms, being separate structures, are quicker to build with minimal noise and mess, offering a more convenient option.

So, garden room or extension?

So, garden rooms vs extensions - what's best? The right solution will depend on various factors and will be different for everyone but if you are thinking about a home extension, it’s definitely worth checking out garden rooms.

2 Permitted Development Rights

Contact Mark on 0115 7722715 or email

A bespoke combined insulated garden room by Cosy Garden Rooms in maintenance free composite cladding.

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