When you work as an architect in Ireland it doesn’t take long to work a couple of things out. One is that architecture barely figures on Irish cultural horizons. Every endeavour strains to support literature, music and drama; that’s where the prizes are – and the public expectations. Architecture is out of sight.

The second is coming to terms with the new, with deeply rooted beliefs that renewal can best be achieved by replacement rather than evolution. These replacements are also usually ideas that have been soundly proven elsewhere rather than having grown out of local conditions. This fuzzy relationship with continuity – we pay it plenty of lip service, and have several layers of obsession with history, but under the surface we have an insouciance about physical place – has significant implications for the fabric left behind: the buildings and the architecture of the past. In a world dominated by heritage thinking, new things are not a crime. In Ireland it’s a kind of odd strength as well as a weakness.

I have always loved the awkward beauty of old structures and thought there was something more to be made of these conditions. There must be some lost chord that would open up Irish views about architecture through an engagement with older buildings, some way that interesting – or even radical – things could happen with them that would provide an original cultural contribution. Finding reasons why old buildings should be reused is not difficult, especially when you think about it in a fairly cold-blooded way: these rooms, facades, roofs, cloisters, galleries, staircases, shops are useful things, attractive prospects in themselves, with interesting spaces and a beautiful patina of aged materials. But it runs deeper than that: in the modern world old buildings also offer a kind of freedom of the mind. In an age of regulation and standardisation their awkward fact endures; approximate shapes and proportions cannot be “explained” or reduced to rules. They offer an embedded resistance to the worst aspects of globalisation: they are specific, about a place; they are an escape route for inventive thought.

These ideas lie behind a book called Palimpsest: Intervention and Change in Irish Architecture. It is the fruit of my travel around the Irish countryside, of exploring ordinary buildings in small towns and open landscape – and of reflection on my projects over several years. Looking beyond standard images of "Irish architecture" – the Rock of Cashel: Ireland's ultimate ruin – it became clear that many traditional buildings are not built at one time but are multidated, evolutionary structures that had grown over centuries: castles, houses and churches but also cottages, barns and towns.

The way they evolved represented intelligent and logical choices with structure and materials – a far cry from the implied whimsicality of old things – and a clear understanding of the symbolic and formal nature of the buildings adjusted.

Many tower houses, for instance, were continually occupied over hundreds of years by people who were fully aware of their heraldic and legitimising nature. Houses were added to them, then new sections were joined on that formalised them at the centre of Palladian compositions. There were specific local ways of doing things that were original and interesting.

Becoming aware of these continuities opened up other questions about Irish history. How did this continual occupation of majestic structures sit with traditional views on the poverty-stricken violent nature of Irish history? As most of them were “impure”, in the sense that they were composite, they were in the main omitted from standard histories of architecture; many of the images in the book have been published for the first time.

"Palimpsest", a word borrowed from painting, and to do with layering of one thing over another, could be extended to interpret similar projects across Europe. It was also clear that, as a way of thinking about architecture, the idea of intelligent change and intervention was going through a renaissance in contemporary thought. Given impetus by the destruction of the second World War, and supported by calls for sustainable development, architects across Europe were designing exciting composite works that conserved existing fabric yet made radical changes or additions to it, creating dramatic environments with a mixture of old and new materials and spaces. Examples such as the Neues Museum in Berlin, designed by David Chipperfield, or the extraordinary Kolumba Museum, in Cologne, by Peter Zumthor – the museum is raised on concrete stilts over the ruins of a church bombed in the second World War – are increasingly at the forefront of design rather than addenda to it.

If an “architecture of change” has a history and a methodology in an Irish context, there has to be a great future for it here – using informed, contemporary architectural practice to define new horizons. Typical Irish buildings are unique in their way; thoughtful work on them could provide pieces of transformative architecture that would be of the place – open and accessible to everybody. Some examples are used in the book. One is the old St Maur’s Church, in the Co Dublin town of Rush, which our practice turned into a library for Fingal County Council: we inserted a timber gallery into the nave to let it work as a public space. Another example is Dublin Dental Hospital, where five houses in the centre of the city gained a series of library pods at roof level. A third is St Mary’s Church in Kilkenny, where lost sections of the original church are being re-created in new materials on archaeologically valid foundations.

Making this happen is not a magic formula. It is more a matter of clearly defined actions based on an assessment and survey of archaeology, history and landscape – which opens up insights into soft spots, where the building can be changed and how. Architecture requires digging around to find a place and character for work; making interventions is akin to designing in a different kind of landscape, with the addition of history, a materiality of worn and rubbed surfaces, and a painterly capacity to reduce the canvas as often as increase it. But while it is contemporary architecture, it is firmly founded on the principles of conservation.

Only certain buildings are valid to even think about making interventions into; when it happens, what is retained is conserved to the highest standard. What is new is clearly identified – and reversible; new things are inserted like a key that opens a new world. Working with them ensures particularity, a way to originality. It’s a way of thinking for the future.

Niall McCullough is a director of McCullough Mulvin Architects; his book Palimpsest: Intervention and Change in Irish Architecture is published by Anne Street Press