Making models from paper, cardboard and balsa wood is a very important part of the modus operandi of Grafton Architects, that small and very talented Dublin-based practice whose work stands comparison with that of their peers, not just in Ireland, but anywhere on the world stage.

Their exhibition at the RIAI's Architecture Centre features an astonishing range of models, large and small, of houses, schools, studios, bridges and apartment buildings.

It is all to do with thinking in three dimensions and trying out this or that solution before deciding on something that feels just right.

Now 20 years old, Grafton Architects struggled through the bleak 1980s, when there was almost no work but a lot of time to think, and they are now reaping rewards for their steadfast dedication to the art of architecture under the inspired leadership of Yvonne Farrell and Shelley McNamara.

"We've grown from three people in 1990 to nine in 1999", says Ms McNamara. Iseult Hall, one of their more recent recruits, joined the office three years ago to make a model of a long, narrow mews project to the rear of 13 Merrion Square "and she's still with us". The model is a tribute to her talent.

One of Grafton's associates, Philippe O'Sullivan (he's from Cavan, but his mother is French), recalls filing down a plaster model of their beautiful bridge over the N11 near Shankill on his way into work on the 46A. Designed in collaboration with engineers Roughan O'Donovan, it is surely among Ireland's finest.

"Bridges are so three-dimensional that it's very important to look at them that way," Mr O'Sullivan says. "As you build a model, you find that something may only work in a drawing. So it makes a huge difference to do model studies early on for bridges or buildings, because you can sculpt as well as draw them".

Unlike others who might be satisfied with two-dimensional drawings or computer-generated images, Grafton Architects want to be in a position to judge the shape of what they are trying to achieve. Three versions of their Boyne suspension bridge near Drogheda, shown projecting from a wall, prove the point.

Naturally, they rationalised the exhibition space in the Architecture Centre to make it fit what they wanted. The centrepiece of the exhibition is a floating MDF beam, with a span of eight metres. "We did something muscular that would reflect our attitude and our approach," says Ms McNamara, tongue in cheek.

"What's good about it is that it shows the connections between projects and the streams of work happening in the office," she feels. There is a sense that even she and her colleagues are somewhat taken aback by the huge volume and variety of work they have managed to produce, much of it within the past five years. It's over coffee in their office on the top floor of Weir's in Grafton Street that every project is discussed. "The eleven o'clock coffee break is sacrosanct for us. It's the one time when everyone can see what's going on. If anyone was to schedule a meeting for 11, they would get shot," according to Ms McNamara.

Though Grafton Architects do not have a "house style", common themes can be identified in their concerns about context, the use of materials and the idea of buildings as sculpted objects in the landscape, whether urban or rural. Everything is carefully considered, as the drawings, models and photographs show.

Recent projects include several schools, all designed within the Department of Education's very tight budget constraint of £659 per square metre (£61 per sq ft). It is difficult to make good architecture at this ludicrously low price, but Grafton Architects manage to do it; their school in Celbridge is truly outstanding.

In each case, the architects have tried to connect new school buildings with the landscape. Thus, the sloping roofs of their Castleblayney project run parallel with the contours of the land.

The building is organised around a two-storey nave with "light scoops" cut out at the top to allow daylight to penetrate the building.

Yvonne Farrell sees the role of a school architect as "just part of a huge collective drive that hundreds of people have been involved in, long before the ribbon is cut" and she pays tribute to "the energy of parents, teachers and school principals who have worked, sometimes for 20 years, to get a project off the ground".

The nave and light scoops appear again in Meath County Council's very forward-looking Civic Offices in Dunshaughlin. Reflecting the current trend towards transparency, the building will not only be see-through but the council chamber itself will be installed in a glass cube; it can also meet 95 per cent of its heating/cooling needs.

Architectural competitions are another preoccupation for Grafton Architects. "Even if we don't win, working on competitions is not necessarily a lost cause," says Gerard Carty, another associate in the practice, "because many ideas that are developed through intense working can be reinterpreted in other work."

But there are much-valued commissions, too, mostly from clients who know their work and have confidence that they will produce the right result. One such client is Frank Hall, an architect-turned-developer who was one of Grafton's founders; his new house in Rathmines shows what can be done on a very tight urban site.

Located beside Corrigan's pub, its exterior combines beautifully made redbrick and granite walls. And despite the small size of the site (measuring just 9.5 by 12.5 metres), it has external spaces on three levels - a yard at street level, a timber deck on the livingroom floor and a small terrace off the main bedroom.

There are other houses featured, one a reinterpretation of the traditional Irish long house in Doolin, Co Clare, with its wonderful qualities of light and enclosure.

P J Mara's holiday home (with two rental apartments) in Kinvara, Co Galway, is also there as are some mews buildings of great distinction near the centre of Dublin.

There have been awards aplenty for Grafton Architects' work, most recently for their mews on Denzille Lane, near Merrion Square, which contains a plush screening room for Clarence Pictures. But this "modern miniature of a Georgian house", as Ms Farrell puts it, also has offices, an apartment and basement parking.

As part of Group 91, they were involved in its seminal project, "Making a Modern Street", which led to this consortium of practices winning the Temple Bar framework plan. Subsequently, Grafton produced a very successful social housing scheme on South Earl Street, in the Liberties, that would put private developers to shame.

This steeled the architects for their shotgun marriage to Zoe Developments, following a Dublin Corporation-inspired competition for a crucial corner site at Church Street and North King Street. An unusual collaboration, it has produced Zoe's most crafted building ever, complete with sliding cedarwood shutters.

Temple Bar Square was Grafton Architects' principal contribution to Group 91's framework plan for Dublin's designated cultural quarter. Though some may find the building's industrial language rather cold, if expressive, Yvonne Farrell and Shelley McNamara remain enthusiastic about the backdrop it provides for the public space.

In the case of their award-winning Department of Mechanical Engineering laboratory in Trinity College, a distinctive basalt cube mounted on a rooflit triangle, it was on such a fast-track timetable that they had to do models and perspectives for a presentation to the board of the college before they had designed the building.

There are lots of other good things in the exhibition, which continues on week days until October 29th, such as a superb office fit-out with all the furniture custom-designed by the architects themselves. Looked at in the round or in detail, this is brilliant work by a great little firm of architects. It proves that small really can be beautiful.