Quality of National Library refurbishment programme will make it well worth the wait

Undoubtedly, one of the most familiar buildings in central Dublin has to be the National Library of Ireland on Kildare Street. Built in the late 1880s to the designs of Sir Thomas Newenham Deane, assisted by his son Thomas Manley Deane, the structure is one of a pair, matched on the other side of Leinster House by the National Museum. Both share an elaborate Italianate style, based around projecting rotundas facing one another across a courtyard. But while the museum still has its original, and recently restored, facade of soft Mountcharles sandstone, that of the library was replaced during the last century by more durable limestone.

At the moment, scaffolding covers the Kildare Street frontage of the National Library, providing tangible evidence of the institution's current £50 million (€63.5m) refurbishment and expansion programme. In fact, this work has been going on for the past couple of years and is likely to continue for some time to come, its progress to some extent hindered by the necessity for the library to continue offering services to the public as well as the importance of providing storage for its ever-expanding collection of material.

Overall responsibility for the entire project lies with the Office of Public Works, with two members of staff, assistant principal architect Klaus Unger and senior architect Stephen Kane, being engaged on this specific work. A site map of the area indicates just how far the National Library has expanded beyond its original walls of late. As envisaged by the Deanes, the building terminates almost immediately behind its rotunda, the adjoining plot on Kildare Street being occupied by the Royal College of Physicians. On either side of the rotunda, the architects planned wings to provide additional facilities. While that to the west (street) side was completed, the eastern wing, which is closest to Leinster House, ran back little more than the depth of a single room, owing to funds running out in 1890. It was extended further back in the mid-1920s but in a very unsatisfactory fashion, with floor levels, for example, being different to those in the older blocks.

Meanwhile, in order to meet the library's need for more space, other buildings were acquired along Kildare Street. The best-known of these is in one section of the former Kildare Street Club; this now houses the heraldic office and the manuscripts department. The two adjoining houses, numbers 4 and 5, are also now part of the library and at present the first of these, distinguished by its 1930s limestone-sheeted front, is being refurbished to provide offices for the institution; this work ought to be completed by the middle of next year, thereby freeing up space in the oldest block.

Juggling with the requirements of the library means OPW has divided the entire scheme into nine separate phases, of which the first three are complete. These are the adaptation of the Kildare Street Club property, the restoration of a former racquet hall on Leinster Lane to accommodate conservation, micro-filming and technical services and - at the top of the same lane - the transformation of the old NCAD site.

The last of these has just been completed at a cost of some £6 million (€7.6m) and provides the best evidence yet of what the National Library will eventually offer to the public. This particular site dates back to the 1820s after Leinster House had been taken over by the Royal Dublin Society, which here installed its drawing school. "The building is of great historical significance," Klaus Unger comments, "and therefore modern interventions have had to be sensitive to its provenance".

The first floor of the structure was designed as an exhibition gallery for students' work and much of its character has been retained - or rather regained - after almost two centuries of use and abuse. Running to approximately 1,000 sq m, the space is divided by a series of Ionic columned screens. The northern wall, which looks towards Trinity College, has been opened up by the insertion of a window running almost full-length and full-width, although light can still be controlled by blinds. Similarly, the room's coved ceiling, rising up above a deep cornice, is now finished by a series of northerly-facing pitched skylights resting on the building's slate roof. A mahogany floor has been installed, beneath which are concealed not just the necessary weight-bearing supports but the relevant electronic and technological devices.

The intention is that this enormous room will act as a centre for one of the library's most popular facilities, its genealogy service, but for the moment, until all the other phases of the library's programme have been completed, it will have to be used for storage space. The same is also true of the building's ground floor, which covers an area almost as great as that above but is more obviously divided into a number of separate areas. That to the north will be a seminar room while the rest of the room is to be an exhibition space, lit in part by large windows to the east which abut the atrium of the new Oireachtas office development completed last year.

On both floors, the architects have had to take into account the historical character of the old NCAD building. The entrance lobby and staircase have provided them with an opportunity to make a more contemporary intervention, thanks to polished Kilkenny marble floors and chrome-topped railings. Then there are the wooden screens in which slender vertical windows acknowledge the fluting of the main hall's Ionic columns.

Both Unger and Kane are even more elated with the exterior of the building, constructed in rough-cut limestone. This has been stripped and repointed with a new facade added on to the south, offering a wall of glass flanked by towers of aluminium panelling. Similarly, on the west side, what is expected to be the eventual entrance to the building now displays a starkly elegant wall of glass and an aluminium canopy over the double doors. As already mentioned, it is unlikely that members of the public will have access to this building for another couple of years due to the phased nature of the National Library project. A particularly tricky element in this work is the nature of the site, hemmed in by existing buildings on almost all sides.

The next section to be tackled is likely to be an area which runs between Kildare Street and Leinster Lane and which terminates at its southern end with the Royal College of Physicians. The intention is to build here a major new book repository running to some 6,500 sq m over seven floors, two below ground and five above; the cost is expected to be in the region of £20 million (€25.4m). The scheme would be undertaken in conjunction with the college, not least because a tunnel would have to be constructed beneath its building to link the repository and the old library.

While planning permission has already been granted for the next phase, no application has yet been made for the redevelopment of the 1925 block behind the main library's east wing or, indeed, for the overhaul of the central section of the old rotunda; together, these tasks would cost a further £20 million (€25.4m). Also on the agenda is work on both the original west wing and the refurbishment of number 5 Kildare Street to act as a centre for processing and cataloguing.

Regular users of the library will be particularly happy to learn that, when all these schemes have concluded, the number of desks available to readers ought to be around 400, more than double the present figure.

Unger and Kane are great advocates of this OPW scheme, with the former insisting, that while work must be phased, they are "thinking not just piecemeal but contextually, having regard to the total urban context". Progress may not be as fast as some, not least the library's staff, might like, but it is clear that the final results will be well worth the wait.