To be, or not to be: that is the stark question hanging over Dublin's iconic Liberty Hall, writes Frank McDonald, Environment Editor.

LIBERTY Hall occupies a special place in the consciousness of Dublin. Love it or loathe it, the city's first "skyscraper" was - and still is - the icon of an earlier era, when Dublin was emerging from the pervasive gloom of the 1950s into a period of relative prosperity and hope for the future.

More than four decades after it was officially opened as the proud new headquarters of the Irish Transport and General Workers Union, and despite all the talk and plans to build higher elsewhere, it retains its status as the tallest building in Dublin with 17 storeys that rise to a height of 60 metres (198 feet).

While it was being built in the early 1960s, Dubliners watched with a mixture of awe and excitement as the reinforced concrete structure rose up from Eden Quay. And when it was finally finished in 1965, Liberty Hall was hailed as a "crystal tower" and an "inspiring monument" for Irish trade unionism.

Some commentators were bowled over. "Under the changing skies of our climate - at night lighted up, or in the daytime - it always looks handsome," said a gushing review in the Irish Builder. "When seen against a blue sky with white clouds sailing over, it has a gossamer quality as charming as a Japanese print scene."

It lost that quality after a bomb exploded outside the building in 1972. Windows were given a reflective shatterproof coating that took away the transparency it once had while security considerations led to the closure of its observation deck. Mosaic cladding on the edge of each floor also fell into decay and has since disappeared.

Last October, after SIPTU announced that the demolition and replacement of Liberty Hall was being seriously considered, nearly 2,000 people from many parts of Ireland availed of the Architecture Foundation's Open House weekend to see its interior for themselves and enjoy views of Dublin from the penthouse level.

Antoinette O'Neill, co-ordinator of Open House, said many visitors were shocked by the idea that the city's tallest building could be lost. "What the huge turnout showed, I think, is that people see Liberty Hall not just as SIPTU's headquarters, but also as something that belongs to them. So there is this sense of public ownership."

Desmond Rea O'Kelly, the structural engineer-architect who designed it, was quite overwhelmed by the response: "They were so enthusiastic that I got the impression they were going to get banners and have a protest march there and then." And naturally, he is upset by the proposal to demolish his magnum opus.

"We all have our vanities, which are hard to suppress," he said. "One of the other things I also regret very much is that Oisín Kelly's great sculpture of the young man and the older man admiring their work was never put up outside Liberty Hall." Ironically, they ended up outside the few-feet-higher Cork County Hall.

Now aged 83, O'Kelly revealed that his inspiration for Liberty Hall was Frank Lloyd Wright's headquarters for Johnson Wax in Wisconsin.

But he denied that the wavy roof of his tower, with its striped undercroft, was a conscious deference to Busáras. As for its fate, he simply said: "Would they kindly leave it alone till I'm gone."

For SIPTU, however, it is little more than jaded, dysfunctional office space. The real problem is that its service core - lifts, stairs, toilets, etc - occupies 40 per cent of the 289sq m (3,111sq ft) floorplate at each level, leaving room for relatively pokey offices around the outer edges laid out along quadrangular corridors.

Thus, re-cladding the tower would not solve the "gross-to-net" floor ratio problem. And since the union has resolved to remain on its historic site, all sorts of alternative options - such as converting the building to residential use, with perhaps two L-shaped apartments per floor - have been ruled out of consideration.

SIPTU may be sentimental about the site, but it clearly has no affection for what stands there. After all, it demolished the original Liberty Hall, which had been restored after being shelled during the 1916 Rising, to make way for the present building; it was from there that the rebels formed up to march to the GPO.

Now, the union is planning to demolish its successor. Joe O'Flynn, its Cork-born general secretary, conceded that the 17-storey tower has an iconic status. "Huge consideration was given to this and, as a national organisation, we have a huge responsibility to ensure that the heritage of the site is respected."

He stressed that SIPTU had no intention of building an eight-storey "square box" simply to maximise the value of this prime city centre site. The development of offices and other facilities which the union had in mind would include a new tower that "should be as elegant as Liberty Hall and become as iconic in time".

SIPTU needs about 5,000sq m (53,820sq ft) of offices, according to Joe O'Flynn. However, to make the project viable, it would include a further 4,000sq m (43,050sq ft) for commercial letting, as well as space for the union's college and a hall to replace the existing one, which was renovated only a few years ago.

But any new tower on the site would obviously be more substantial than the existing building. If it is to have a floorplate of, say, 600sq m (6,458sq ft), it would inevitably need to be taller to achieve an appropriate "slenderness ratio". At a minimum, therefore, it would rise to 87.5 metres - nearly 50 per cent higher.

A design brief for an architectural competition to find such a replacement is now being finalised, and the intention is to advertise it in the EU's Official Journal. From the expressions of interest, a SIPTU-dominated jury would select a shortlist of entrants for interview and, finally, an architect would be chosen.

Veteran Dublin architect Brian Hogan, who is advising the union, described Liberty Hall as a more high-profile case of older office blocks becoming obsolete: "They have a shorter and shorter lifespan these days. I've seen buildings I've worked on myself being demolished, but I don't have strong sentimental views."

When Liberty Hall was designed in 1958, the ITGWU was organised in small branches for which cellular office space was quite adequate; it was not the corporate body that SIPTU has become. "The original building was replaced in the 1960s, but time has moved on and we need to meet the requirements of the age."

It will be a matter for Dublin City Council's planners to decide, or perhaps even the councillors themselves. With the much less prominent Bank of Ireland in Baggot Street in the process of being made a protected structure, the fate of Liberty Hall needs careful consideration and much more public debate.