O'Donnell and Tuomey's story-based architecture has proved a succesful way of applying Irish literary tradition to the visual arts, writes Emma Cullinan

This is a house of contradictions and counterbalances, and it causes the mind to wrestle with these right from the first view of it: it is a large abode, at 500sq m (5,398sq ft), and yet it closely hugs, and flows over its hollowed rocky site. Also, because it is first seen from above (before descending its steep drive), it it is distant and interesting rather than in-your-face overwhelming. This is what design guidelines have been begging people to do with houses: respecting the site and its contours rather than heralding from the hilltop.

Another counterbalance is between the building's heaviness and lightness, provided by varying textures in the walls: from the structural rock at the base of the walls, to the varying shapes of glass above and the concrete roof panels which sparkle from the granite within them.

Both outside and within, the building is busy and yet calm at them same time. Staircases narrow and widen, many working as secret passages reached through unexpected doorways. Rooms connect to rooms they are not conventionally meant to (except now you realise that they should: it makes sense that a child's bedroom has a tiny door into the kitchen for early morning wake-ups and quick access to parents and cereal). The ceilings slope upwards and downwards bearing little relation to what the spaces below it are doing.

"It was a risk," says John Tuomey, about how this house evolved. He and Sheila O'Donnell had no idea what it would look like when they began and, certainly, in the wrong hands this could have been a mess. O'Donnell and Tuomey have gained a reputation for the care they take over buildings, and also for evolving style, from references to post-modernism (such as in the Children's Court in Smithfield by John Tuomey, and perhaps derived from time spent working with Jim Stirling in London), through pared, carefully detailed structures, to more organic buildings. That is why, when faced with this home of copious levels resembling a wobbly, long diamond in plan, you know that it has structured thinking behind it: it has been in the hands of a composer creating a tune rather than someone throwing random notes onto a stave.

The practice also develops stories around its buildings, many of which relate to nature, whether responding intimately to a site - such as with the Glucksman Gallery in Cork, which was formed by steering clear of the surrounding trees, to the new Photographer's Gallery the practice is designing in a thin street off London's Oxford Street. The story goes that the narrow road is like a seismic crack and the resulting building, with its neatly contained stacked boxes, is configured as if it slipped when the earth moved.

This Killiney house is "like a kicked can" says Tuomey, describing how it is shaped by the surrounding rock, terraced garden and lawn.

The property has also been personified as a sleeping giant. It's head faces the sea (its brain is an office) and its legs are the children's bedrooms.

It is also a metaphorical pile of rocks. "We wanted the house to be like a terraced landscape where you could climb from platform to platform," says John.

So, unlike with many clients who may be presented with axonometrics and computerised pictures of the finished building, filled with happy people, the clients here got a watercolour from Sheila of generous rocks (almost boulders), "and the finished house retained that form," says the client. This painting showed how the enormous building would comprise definite parts.

The other picture they received was a line drawing, by John, of a giant lying on its side with its face fronting onto the sea and its gently bent legs pointing towards Dublin city. As well as storylines the house is also a bit of a storybook, says Tuomey.

And like a book, you can't grab the whole story at once: you need to move through it to discover it.

There are those skewed stairs, secret passages, unexpected doorways, varying levels and captured viewpoints, for instance from the masterbedroom across a glass vault above the kitchen and through to the sea, and another view of the Sugarloaf. In the children's rooms wardrobes in one room have backs that open into a sibling's space. The front door tushers you straight up narrow dramatically sloped stairs and is as if the house bends down to meet you, says Tuomey. I'm reminded of Oscar Wilde's Selfish Giant bending down to lift a snow-spattered boy up into a tree, and sunlight.

It is often said that Ireland has a literary tradition rather than a visual one and such architectural storytelling is an ingenious way of using one art form that we are comfortable with to describe and create another.

It took a lot of cardboard models to make a rock pile into realty (sic) and the faceted roofs, angular spaces and souring overhangs are anchored by a large chimney (or tent peg) and central wall acting as a backbone.

It is one thing designing such a complex struture, the other is having to build it. Gem Manufacturing made 3D templates to ensure accuracy where timber joins the ceiling and Townlink Construction's concrete work was superb says Tuomey. "The accuracy of the Polish concrete workers was alarming."

In typical O'Donnell and Tuomey style the iroko, concrete and lime render is untreated and will be left to weather.

It will be interesting to see what happens to the colour and structure of that heavy concrete roof, weighing down on the building to create the cave-like effect the architects were after.

This respect for the properties of nature is carried through in the organic shape of the house.

In fact, such was John Tuomey's respect for the site he almost felt it would be better if nothing was built here. The first task was to demolish the 1950s house already on the site which, remarkably but, given some of the monstrosities that have been built countrywide, perhaps not surprisingly, didn't address the sea at all but instead turned its back to the water.

"It's about slightly setting the building aside and enhancing the landscape so people might say what a beautiful place rather tan what a beautiful building," says Tuomey. "If you sit with your back against a rock and look at sea you couldn't be happier: why should a house kill that?"

The practice's move towards curvier structures began with a house in Howth where a walls bends to capture a view of Ireland's Eye. The architects are less worried about what the building will look like from the start and more concerned about the design journey in response to lives and sites.

We are back to nature - this time people: "The forms of building can flex like humans do," says Tuomey understanding how nature resonates with us: "Things should be strangely familiar: a bit strange but also part of background. You should feel at ease but also prodded by something a bit different and awake to yourself."

The clients certainly feel comfortable but challenged by their new home. They have what they wanted: a key part of the brief was the ability to be able to say hello to the sea at breakfast time each morning, and that the kitchen be in the centre of the house. But of the owners admits she hasn't dared invite anyone over yet because she is not sure that it would give the right impression of her personality and you do get the feeling that someone has commissioned a pretty picture and ended up with a Miro or a Rothko.

The house itself feels like a gallery but it's not stern; it's brave, it's challenging, it offers many moments of sheer delight and shows the way that architecture may be moving, away from simple boxes into more complex structures.

"It is magnificent," says the owner and she means that both objectively and subjectively.