It may seem the safe option to add extensions onto buildings in the same style as the original but the result will lack authenticity, writes Emma Cullinan

IT'S A complete eyesore, complained one man to the planning authorities when he saw his neighbour's contemporary extension being added to a Georgian house, and many would agree with him.

Indeed, there are plenty of conservatory companies providing off-the-peg Victorian and Edwardian-style additions to the rear of houses who are doing very well with them.

So why is it that you will never find an extension by any of the most talented architects in Ireland that look like the period building it's attached to?

There are a few reasons and one of them is fundamental to an architect's design integrity. "We don't do pastiche because we don't enjoy it and we have no faith or belief in it," says Liam Tuite, partner in Kavanagh Tuite Architects.

Yet this is not just about the principles of individual architects, there is a whole debate about the treatment of valuable old buildings. It's not just modern architects who think along these lines; most conservationists will also insist on a clear distinction between what is old and what is new. The main aim being to preserve as much of the old, without compromising it.

The need for guidance and international agreement on this issue led to the signing of the Venice Charter in 1964. One of its tenets was that: "The process of restoration is a highly specialised operation. Its aim is to preserve and reveal the aesthetic and historic value of the monument and is based on respect for original material . . . it must stop at the point where conjecture begins, and . . . any extra work which is indispensable must be distinct from the architectural composition and must bear a contemporary stamp."

This wasn't the last word on the subject - there is still debate and much faking of old buildings - but it is generally accepted as the way to work among those who are prominent in conservation and architecture.

One body which did adopt the charter was the UNESCO-sponsored organisation ICOMOS (International Council on Monuments and Sites) and a member of its Irish Council, Margaret Gowen (who runs an archeological consultancy practice), wrote in the book Period house a conservation guidance manual, compiled and edited by Frank Keohane: "Fake reconstruction is no replacement for historic fabric. A reconstructed building will never possess the character and resonance of the original. Good modern design needs to be promoted in historic core areas where the original fabric is gone, but it must harmonise and achieve a balance in this context.

"Reconstruction," she goes on, "occurs and can be motivated by a number of factors. These often include: romantic confusion; illusion that modern craft can represent genuine historic value; confusion of historic knowledge; exploitation of historic building style for poorly thought out design and economic purposes."

Tuite agrees: "In a way you disrespect the original work when you redo it falsely, with new materials, and try to make it look like something else. You need to conserve and respect what's there. Don't pretend that you did it; don't pretend that you thought of it."

Kavanagh Tuite rarely do domestic projects, although they have worked on aspects of Rolling Stone Ronnie Wood's home in Ireland over a number of years. One of their conservation jobs is on an old house, though. The Nova Innovation Centre at UCD is in Merville House, built around 1750 for Lord Foster. A glass corridor added by Brian Kavanagh of Kavanagh Tuite clearly distinguishes between old and new: "That follows the philosophy about conserving and repairing what is old and worth keeping while what's added to it is of its time and is as good as we can make it," says Tuite.

Examples of where new styles have been added onto old include the curved glass roofs over both the Reichstag in Berlin and the British Museum in London, by Foster and Partners. Both are stunning, and publicity eliciting. In the glass-covered restaurant in the extension to the National Gallery in Dublin (by Benson + Forsyth), you can view the brick wall of the older building to one side. Glass also spans the gap between the Hugh Lane gallery in Parnell Square and the period building next door - the glass revealing part of a new extension built in behind it (by Gilroy McMahon Architects).

Glass has proved a good material with which to add new buildings onto old because it allows view of the old and it was something that probably became popular when Italian architect Carlo Scarpa restored and added to the Castelvecchio museum in Verona (in 1954). He used glass and traditional materials to display the best of the old and add in new parts, such as glass panels which almost seem to slide out from beneath the original structure.

Materials from different historical eras were used beside each other but kept apart. New floors stopped short of the walls, while the walls didn't reach the ceilings. Many of the new materials were of their place, such as the local Prun stone.

Scarpa's work also showed a respect for craft - and he would involve himself in long conversations with craftsmen - and a regard for and knowledge of history. This could then be worked with, as Scarpa said: "I decided to introduce some vertical elements to break up the symmetry as the Gothic demanded; Gothic, especially in its Venetian form, is not very symmetrical."

So historical knowledge can be used to the strengthen the new. After all, avant gard artists, such as Picasso and Matisse, began with traditional techniques and always maintained a link with classicism and tradition while creating new types of art.

Knowledge of the new can also be brought to bear on the old. In Castelvecchio, Scarpa used the open corner windows, that had been features of more recent architecture, to achieve diffusion of light across wall surfaces rather than create direct glare from windows set in the middle of walls (something that architects O'Donnell and Tuomey achieved in the Glucksman Gallery in Cork with corner apertures).

Yet a knowledge of historical building types doesn't necessarily bring with it the skill to replicate it. The lack of craftsmanship nowadays tends to lead to clunky looking details that are machine made.

"I think we design better as modern architects by being true to what we know about. I think if we tried to ape Victorian and Georgian architecture we would do it unconvincingly and I've never seen it done convincingly," says Tuite. "I cannot think of a single extension that was done in the style of a traditional house that was convincing or worked well.

"There's not the craftsmanship and there isn't even the skill in proportion. We are trained in a different way."

Warnings about the risks involved in replicating the old came as far back as 1914, when Otto Wagner wrote that the future of architecture lay with the development of new forms suited to new materials, not with the reworking of historical styles. Such new materials should bring new skills, thought Frank Lloyd Wright: "Every new material means a new form, a new use if used according to its nature."

Another reason for designing in new ways, says Tuite, is that we live differently now. "Space is at a premium. Families are living in decent but relatively small houses in Irish towns and we engage more with the exterior. If you extend a house very well you can unlock it: so rather than retaining it as a group of internal spaces you take some part of it and create an interplay between it and the outside and create a whole new dimension to that house. You give it a new lease of life.

"If you take the spaces that are there and look after and repair them and then add something that is an entirely different way of thinking about it, you add to it and create a better place to live."

The form of an extension doesn't have to be a plain glass box - and there are plenty of examples of new extensions that are in different materials.

"The problem is that simple glass boxes were done by skilled architects in the beginning but now they are being done by non-architects and unskilled architects," says Tuite, who says that he is tiring of the form. This brings us back to attempts at recreating what has gone before - whether that is a Georgian gem or a Miesian crystal palace - and not having the skill, material, time or equipment to do so.

"You need to have absolute respect for the history. You are not discarding it by doing something different. You can improve it and open it up," says Tuite. "If you copy it you are likely to degrade it."