Ireland is a key player in the global promotion of the use of lime in buildings. Emma Cullinan talks to Grainne Shaffrey about her part in this

Lime as a building material has been with us for centuries - indeed Ireland's period buildings are held together with it - but in the recent past its use has been concreted over by less demanding substances. Yet that could change: last week the Irish branch of the Building Limes Forum was launched at the Irish Architectural Archive in Merrion Square, a building itself restored using lime.

The Irish Forum was already in existence but now it has official recognition as part of an international network of Limes Forums, and it has just achieved charitable status.

While courses on lime are run by institutions such as the RIAI and the Dublin Civic Trust, the sharing of experience and research happens through the forum.

The resurgence of lime in buildings - as a render, plaster, mortar and colour wash - has grown in tandem with the greater care taken over the conservation of buildings. To do the job properly - and to qualify for one of the many grants available - conservation architects and contractors have to know their lime.

Its qualities are such that architects are using it in new buildings too: Howley Harrington Architects used lime in its local authority housing scheme at Balgaddy in west Dublin and architect Grainne Shaffrey, of Shaffrey Associates, is using it in a new library and council offices in Cavan.

In this case, Shaffrey is practising what she preaches, as she is the chairperson of Building Limes Forum Ireland, although she is quick to point out that this is an organisation of equals. "There's a great generosity in the sharing of information. Communication is one of the Building Limes Forum's great strengths. It's healthy to break down the hierarchy that is in all parts of society but very much in the building industry. You don't normally get the architect and the plasterer communicating but it actually helps to encourage mutual respect. Communicating at an equal pitch can be humbling and there's no harm in architects being brought down a peg or two."

Lime information crosses country boundaries with emails bouncing between experts worldwide, with especially strong representation in the Nordic countries, America and Britain. The forums also meet at international lime conferences. Members include builders, clients, architects, manufacturers and scientists: anyone with an interest in lime can join. "It's about building up everybody's knowledge," says Shaffrey, who works in the firm started by her father Patrick and late mother Maura. Having studied architecture, she says that she fell into her parents' practice by mistake but her full-face grin indicates that this was a happy landing.

So what is this substance that arouses so much passion? Lime has various qualities, one of which is its breathability: it absorbs moisture from the air. "It makes buildings more comfortable to be in," argues Shaffrey, "and it addresses the concerns about sealed buildings and toxic moulds." It's seen as more environmentally-friendly because the limestone used to make it is fired at a lower temperature than that used to create cement, and lime reabsorbs carbon dioxide as it sets. Brick recycling is often easier with lime, because it is simpler to remove than cement.

Lime is usually more flexible than cement (depending on the mix) and more forgiving of small movements in a building: its use can even negate the need for expansion joints. Its gentleness is one reason why it's used in conservation: "When doing repairs, you want the repair to be slightly weaker than the original material," says Shaffrey, "because if anything wears away you want to it to be the newer substance."

While lime is used to repair historic buildings, it is now being used on more recent projects, such as the 1930s Isokon flats in London by Wells Coates. It seems strange to use lime on an iconic concrete building, but Shaffrey points out that the promotion of lime use is not necessarily anti-cement: the materials both have their place in buildings.

Architects also talk of the aesthetic qualities of lime, the fact that the calcite crystals within it refract light in a way that creates a soft texture and bright lustre. There's also a childlike pleasure to be had from investigating the properties of various sands to be used in the mix. The final colour often sits more beautifully between bricks than dull grey cement, says Shaffrey.

Lime fell out of general use because the building industry sought more reliable materials: cement, for instance, can be used in all weathers whereas lime doesn't like frost. Lime does involve more careful job management and specification, for example, in bricklaying, after each layer has been laid, it needs to to settle. This can mean the job will involve moving to different walls, while waiting for the last one to settle.

Understanding the properties of a substance such as lime can teach you a lot about how all materials in a building work, says Shaffrey. "It does require more care and it is a little bit more demanding but it makes you aware of other aspects of site practice."

She is certainly happy to accommodate its characteristics. At a time when the world is questioning the "advances" of the last century or so, Shaffrey is an exponent of the slow cities movement. "It's like the slow food movement," she says. "We understand that raw cheese makers and wine makers need a certain amount of time for those products to reach maturity. Nobody is looking to rush that. Yet we're being asked to accelerate the time that's right for a building, for instance, by not giving plaster time to dry out. A relatively short time is needed to make sure there's not all this stress happening and that materials aren't upset with each other. For a building to last you have to work the materials and structural techniques properly."

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