Thousands of historic buildings across Britain will be opening their doors this month as part of the European Heritage Days initiative.

The scheme, launched by the Council of Europe in 1991, is designed to encourage people to celebrate the rich cultural heritage across the continent. Events have already taken place at the end of August in the Republic of Ireland, while a month-long programme at sites across Scotland and Wales started on 6 September. A series of events will also be taking place in England and Northern Ireland in the next fortnight.

More than 3,500 sites, some of which are usually closed off, will be opened to the public in England, with a further 200 more in Wales, 230 in Northern Ireland and 160 in Scotland. National civic trusts will be involved in organising the series of events in Wales, Scotland and England, as well as the Northern Ireland Environment and Heritage Service, and support will be provided by a range of public bodies including Historic Scotland, English Heritage and Cadw – Welsh Historic Monuments.

Philip Kolvin, chair of the Civic Trust in England, said: "Visitors are invited into places that are otherwise private, to meet people who live or work there, or who know the history of the place better than anyone else. Buildings may be fascinating and awe-inspiring because of their beauty, style or status, but it is the stories they can tell which make them dearer and bring them closer to us." Heritage Open Day events will be held in England between 11 and 14 September; in Northern Ireland between 13 and 14 September; and in Wales and Scotland over the first three weekends of September.