From a distance, St Mathias's Church on the Glen Road in Belfast looks like it belongs on the set of The Little House on the Prairie. At the front stands a spartan little porch and above it a cute bell tower. You can almost picture the Ingalls family walking cheerily, hand in hand, through the front door.

On closer inspection visitors will be amazed to discover that the structure is not made of wood or even bricks, but is fashioned from a material more commonly associated with farmyard buildings: corrugated iron. It is the unusual grooved structure of the building that has led to controversy about the fate of what locals call their "wee tin church".

In the past few weeks, the local clergy have applied for planning permission to demolish the building to make way for a new church and 70 car-parking spaces. Dismayed at the prospect, heritage and architectural groups have embarked on a campaign to protect St Mathias's, the only church of its kind in Belfast, from the ravages of the wrecking ball.

St Mathias's, formerly a Church of Ireland property, is one of a small number of metal places of worship made to order in the late 19th century, rather in the manner one orders large pieces of furniture today. Examples can be found locally in Donegal, Fermanagh and Leitrim, and further afield in Scotland, Iceland and Australia.

First opened in 1892 as the Church of Ireland's St Luke's Mission, St Mathias's was reconsecrated as a Catholic church in 1970. Rita Harkin, research officer with the Ulster Architectural and Heritage Society, says that corrugated iron was used for a variety of portable structures because it was cheap and quick to build. "It was also easy to transport," she explains. "Churches were often sent off in flat packs to the colonies. Their production would usually have occurred in areas of heavy industry; in Belfast, Harland and Wolff shipyard provided these in lull periods."

According to local Sinn Fein councillor Tom Hartley, who is also involved in a campaign to have the building listed, the construction of metal churches began around the time of the population explosion during the late 1800s. "Because of this trend and because local populations tended to be relatively poor, there was neither time nor money to build stone churches" he says. Hartley believes that, as well as being aesthetically beneficial to the West Belfast area, its mixed religious history means it has become "an important reflection of the social history and the shifting demographics of the area".

But local priest Father Brendan Beagon insists that, before the current row erupted, nobody had ever come to visit the church for cultural, architectural or aesthetic reasons. He points to a report drawn up by an engineering firm in 1996 which said that, due to the deterioration in its condition, particularly the foundations, the building should be replaced within 10 years. "Four members of the local clergy recently conducted a door-to-door survey of the neighbourhood explaining the proposals for a new church and the demolition of the existing one. Nobody I spoke to objected to the plans," he says.

At 10 a.m. last Thursday, the tiny church was packed to its arched wooden rafters as Father Beagon said Mass. "It's 'olde worlde' and I'm 'olde worlde', and that is why I like it," said Joan Pimley who has been coming to the church for 50 years. "Equally, though, I can see their point. They say it is in a bad state of disrepair."

Organist Patricia McArdle said St Mathias's had a "lovely atmosphere" and was different to any other church she had ever played in. "It would be a shame to knock it down, but I suppose you have to move with the times." An elderly man who didn't want to be named described the church as "old, cold and leaky". "It's past its sell-by date," he insisted.

Barry O'Reilly, an archaeologist and architectural historian from Dublin has completed a study of corrugated buildings across Ireland and is intending to write a book on the subject. He says the church on the Glen Road is "very rare indeed". "I have found only eight churches of this kind that are still in use in Ireland. They are very much appreciated by their congregations; and in Sallins, Co Kildare, in 1980, local people managed to reverse a decision to have their metal church demolished," he explains.

The attraction for O'Reilly in such structures is "the human scale of the building, the soft, folksy architecture and the way they were built and bolted together". He believes plans for a new church on the Glen Road should incorporate the existing one.

"Or as a last resort, it could be dismantled and built again on another site," he adds.

For his part, Father Beagon has said he has no objections to the latter proposal. Or as Rita Harkin of the Ulster Architectural and Heritage Society asks: "Any takers for this tin treasure?".

The Ulster Architectural and Heritage Society can be reached by calling 04890-550213