What’s the Difference Between a Garden Room and a Garden Annexe?

A garden room and a garden annexe can look surprisingly similar from the outside, but they're designed for very different purposes.

Put simply, a garden room is generally an additional leisure, hobby or working space, while a garden annexe is designed and specified as accommodation in which someone can live comfortably throughout the year.

That difference affects almost everything: the structure, foundations, insulation, services, internal specification and, ultimately, the price.

Is a garden annexe just a more expensive garden room?

No. Although some garden room companies offer products described as annexes, it's important to look beyond the name and understand exactly what you're buying.

A home office that's occupied for seven or eight hours during the working day has very different requirements from a building intended to provide someone's home 24 hours a day, 365 days a year.

A genuine residential annexe therefore needs to be designed around permanent living from the outset.

Construction and materials

One of the biggest differences is the construction specification.

Garden rooms can be manufactured using several different building systems, including Structural Insulated Panels (SIPs). These can provide a quick and effective method of constructing a garden building.

For our garden annexes, however, we use a traditional timber-frame construction system, with the structural components precision-cut in our factory before being assembled on site.

The entire building envelope — walls, floor and roof — is designed around the thermal and structural requirements of a building intended for year-round occupation.

Foundations

What the building sits on is equally important.

Some garden rooms use systems such as ground screws, which can provide a quick and relatively straightforward foundation solution for suitable garden buildings.

Our annexes are normally installed on an engineered concrete raft foundation.

This provides a substantial permanent base for a building that will contain a kitchen, bathroom, furniture, appliances and all the other elements associated with everyday residential use.

The appropriate foundation ultimately depends upon the building, site and ground conditions.

Insulation and year-round comfort

An annexe needs to remain comfortable throughout the year.

That means considering the complete thermal envelope rather than simply adding insulation to the walls.

The floor, walls, roof, windows, doors and junctions between different elements all contribute to the building's thermal performance.

For somebody living in the annexe permanently, this affects not only comfort during very cold or hot weather but also the amount of energy required to heat the building.

A garden annexe needs proper services

This is another major distinction.

Most garden rooms will require an electricity supply, but a self-contained garden annexe normally needs considerably more.

We typically consider four principal services:

• Electricity

• Data/internet

• Fresh water

• Wastewater/sewage

These need to be properly planned and connected between the main property and the annexe.

For our installations, this usually involves creating a service trench between the house and annexe through which the required services can be routed.

Water has to reach the annexe, while wastewater from the kitchen and bathroom needs an appropriate route back to the property's drainage system.

Why does a garden annexe cost more than a garden room?

The difference in price becomes much easier to understand once you compare the complete specification.

You're not simply paying for a larger or more luxurious garden building.

A properly specified garden annexe incorporates the structure, foundations, thermal performance, services and internal facilities required to create a comfortable home.

That's fundamentally different from specifying a building primarily as a home office, gym, studio or occasional leisure space.

Garden room or garden annexe: which do you need?

The starting point should always be how the building will actually be used.

If you want additional space for working, exercising, hobbies or entertaining, a garden room may be entirely appropriate.

If you're creating independent accommodation for a parent or other family member to live in throughout the year, you should be looking at a building designed and specified as a garden annexe from the outset.

At Garden Annexes, our buildings are designed specifically around that requirement: creating comfortable, self-contained living accommodation for year-round use.