Dáil Éireann - Volume 569 - 25 June, 2003

Written Answers. - Historical Sites.

[953]   274. Mr. McGuinness asked the Minister for the Environment, Heritage and Local Government, further to Parliamentary Question No. 120 of 12 June 2003, the reason Dúchas needs to experiment with lime mortar mixes for nearly six months when it has been using it on buildings, such as Kells Priory, for decades and regarding which there is a great deal of literature and technical advice available; the rationale for the need for the experiment; the ratio of lime to sand which has now been decided on; the difference in each case; his views on whether Dúchas has made a discovery regarding lime mortar use to which the attention of restorers of heritage buildings should be drawn; and if he will make a statement on the matter. [17953/03]

  Minister for the Environment, Heritage and Local Government (Mr. Cullen): The specification of lime mortars for conservation works is recognised internationally as a complex and evolving process. Present best practice favours the use of non-hydraulic mortars with the addition of “pozzolans” or additives to impart the appropriate degree of strength for the circumstance in which the mortars are to be used. This practice is an improvement over the use of cementitious mortars, which have been demonstrated to have adverse effects in the long-term on the integrity of structures that were originally constructed, and for centuries repaired, in lime mortar.

  This approach does not permit the use of a single standard specification and there is expert consensus that tailoring the mix to the particular conditions of the site is essential. Although the aggregate used in the mixtures for the works may change, as may the proportions of pozzolans added in, the ratio of aggregate to lime in Kells remains at present at three to one. Detailed work regarding the use of variations in lime mortar mixes has been carried out by my Department and presented to the Building Limes Forum, an international group of expert conservationists formed to research and promote the use of lime in conservation works, at its annual gathering in Kilkenny in September 2002.