REPAIRS AT SLIGO CATHEDRAL
UPDATE – 19th JANUARY 2017
This week we have received a further update from Christ Southgate, Conservation Engineer with Southgate Associates of Cork who are overseeing the repairs to the south east and south west turrets of our Cathedral. Both towers have been re-pointed and where the masonry was found to be quite thin extra stone has been pinned and pointed into position. Further grouting will be carried out on the inside faces of the towers which will further strengthen both. Some movement has been detected in the stonework of the south east turret roof which has been attributed to frost action. Following remedial grouting to the roof the conservators see no need for structural pinning to take place but the whole roof will be subject to repairs. Deep cracks in the stone structure will be filled appropriately and a multi layer special water repellent treatment will complete the work. Following the removal of the scaffolding and protection surrounding the turrets both will continue to be monitored for performance. Only then can a decision be made to establish whether further treatment may be required to the sand and cement pointing. Mr Southgate is scheduled to make a further site visit in one month’s time to inspect the south west turret grouting. In the meantime the interior of the south east tower will be brushed down, any loose or damaged lime plaster will be removed and replaced. The interior walls will then receive two coats of a special clay based paint that is supplied by Stoneware Studios of Youghal. The conservation team will then move on to inspect the Altar to St Joseph which is also suffering from the ingress of water through the fabric of the building.
Essential repair work commenced in the early days of September 2016 when we saw the scaffolding ascend the south tower at the entrance to our Cathedral. As inspection work continued it was established that the north tower too was in need of urgent attention.
Our magnificent church with it’s splendid structure and interior is so familiar and well loved to us all that it is simply known by locals as ‘the Cathedral’. It is a constant presence in our town and in our hearts. Countless numbers have marked the pivotal, central points of their lives and those of loved ones within it’s walls. War and wind, peace and precipitation outside; the world has raged and turned but all remains calm and tranquil within the embrace of our beloved church. Over the generations it has witnessed innumerable historical events with pomp and ceremony, special occasions and celebrations beyond count. But most importantly of all it has provided sanctuary, social, economic and spiritual support and a offered haven for those in need.
‘The Cathedral’ belongs to us all. We are blessed to have it at the core of our community. It is our duty to ensure it remains preserved for future generations. Please see below an outline of the works being carried out together with an explanation of their necessity.
We wish to express our sincere thanks for all your patience and understanding and will keep you informed of progress as work proceeds.
Pointing and Grouting of the South West tower at Sligo Cathedral
Chris Southgate Conservation Engineer
The Cathedral of the Immaculate Conception was opened on 26 July 1874 by Cardinal Paul Cullen of Dublin[ and consecrated on 1 July 1897.] The cathedral is built in a Norman style, and it is the only Norman styled cathedral in Ireland and is of Regional Significance architecturally and dearly loved by the devoted parishioners
Like many fine Victorian churches, it was built meticulously in cut limestone ashlar where the stones are accurately formed to exact rectangles. This required an extraordinary skill form the masons, who had to ensure a fine tolerance for the joint and the stones were often set on lead shims during bedding. In order to facilitate this the stone was often cut to a high tolerance at the front and then the joint sloped away at the rear to allow a thicker bed behind the façade stones. There was a more informal random rubble construction which can be quite permeable behind. Limestone is quite impermeable but is set in lime mortar which is allowed to breathe. As wind and rain hit the surface of masonry the moisture is allowed to absorb into the mortar and release again in dry conditions.
There are a number of factors which can upset this natural process of absorption and drying out.
Firstly the cathedral was repointed in a hard cement pointing which has a tendency to crack allowing minute quantities of moisture in but moisture is subsequently unable to escape getting into the soft rubble stone core and passing into the building.
Secondly it was sometimes difficult to ensure bedding mortar for such a fine joint during original construction and the pointing mortar has nothing behind it.
Thirdly even if the original pointing mortar was correctly installed it sometimes becomes eroded by moisture and exposure.
Lastly the climate change in recent years has subjected buildings such as Sligo Cathedral to intense wind and rain often occurring almost horizontally.
Not surprisingly Sligo Cathedral is suffering from water ingress and a regime of pointing and grouting has been recommended on the roof of the South Tower. Inspections showed no bedding mortar in the roof behind the pointing which has failed due to erosion and this will be replaced with a lime mortar and grout to get back into the thin joints. The grout which is also lime based will be introduced through a special syringe and designed to flow back into the original bed joints.
The main pointing in the tower although not ideal (sand and cement) is at least in good condition and mirrors the general pointing condition of the entire cathedral. In this case only defective areas are to be repointed and we have recommended a special water repellent which has been very effective on similar buildings. The top area of the tower is to be treated and compared with the lower area which will remain untreated. It is hoped that the water repellent which is relatively cheap to apply will be successful in transforming the performance of the Cathedral without the need to repoint.
This the initial project is aimed not only to sort out water ingress in the tower under consideration but also to give an indication of the potential improvement in performance for the whole building.
The specialist work is to be carried out by Michael MC Hale under the supervision of the main contractor and Southgate Associates will provide John Fahy Architect with the specialist experience and advice.
Many similar buildings are experiencing damp problems and we hope that this careful approach will give the necessary feedback and information to carry out a focused repair and conservation regime in the future. The objective will be to do as little as possible and as much as is necessary.
Chris Southgate MA MIStructE FIEI C Eng Conservation Engineer