Extensions can add something special to a house - perhaps even to your life, writes Emma Cullinan

While extensions are naturally about extending your living space they offer more than that: they can extend, or rather enhance, your quality of life; extend the design parameters of your home; and increase your link with your outside space.

Extending rather than moving to another home means that you needn't leave a neighbourhood you like and you won't have to adapt your life to someone else's space.

You will have had time to get to know your own home and how the living space can be improved.

You already own the land that the building will go onto and, if the extension is small enough, you won't even need to apply for planning permission (assuming your house isn't listed).

Also, there'll be no estate agents and probably no lawyers involved.

While building a whole new home may be a daunting prospect, adding an extension allows a foray into the world of architecture on a relatively small scale. And you will be able to design something that suits you exactly.

House Plus - imaginative ideas for extending your home by Phyllis Richardson (Thames and Hudson, £24.95, €36.92) shows the many ways in which people have allowed themselves to dream a little.

While an extension can merely be another bedroom or livingroom tacked onto the house, with a little thought it can add to the overall space by perhaps bringing in more natural light or allowing you to build with materials you love, such as glass, steel, timber or stone.

Some people have also gone beyond just extending their living space, and have added a luxury, such as a swimming pool annex (this includes the Springett Mackay designed pool house in Co Cork, in this book).

The book shows where, rather than simply adding a dull lean-to the their homes, people have expanded the way they live.

Many London houses have used a lot of glass - allowing for a paler imitation of life in a warmer climate. With the insulation properties of glass improving, and with its increasing ability to resist rainwater, it is now possible to sit "outside" all year round and people have grabbed that opportunity. As a contrast, extensions in California, Palm Springs, Mallorca, Italy and Japan have addressed their warmer climates by using roofs which overhang terraces and decks, allowing occupants to spend time outside, under cover. Many will also add in swimming pools or reflecting pools beside these overhangs to make use of water's cooling properties.

The book covers extensions that are added onto roofs; to the back of homes; to the sides of houses; down into basements and extensions that are added all round a home.

The strangest looking one is in Wisconsin where a house looks as if it has been enveloped by an amorous titanium jellyfish.

Extending downwards has enabled those living on hillsides to reverse structures into the incline, meeting their host houses at basement level.

One such extension, in California, has tilted walls and angled staircases, giving the space a sculptural feel and adding liveliness to an underground area. Glass light wells bring in natural light from above.

So rather than just being another room - as important as that may be - this book underlines the fact that extensions can add that something special to a house and, dare I say it, even your life.