Press release
The Four Courts– Repair Works to Dome
Published on
Last updated on
Published on
Last updated on
As keen observers along Dublin’s quays may have noted the veil of mesh and scaffolding that has been draped over the Four Courts Dome over the last few years is slowly beginning to drop.
The OPW completed the enabling, investigative and entablature repairs works to the Four Courts Dome at the end of July 2021. The scaffold that facilitated this phase of investigations and repairs will be dismantled over the court’s recess period of August and September 2021, to minimise disturbance to the Courts Service.
A further final phase of repair works is required to the decorative stone capitals which support the Dome. The investigative findings will be reviewed and works are anticipated to be be tendered in early 2022 and commence on-site in autumn 2022.
In 2011, a section of one of the capitals fell onto the roof of the Four Courts below, necessitating the installation of catch netting to mitigate the immediate risk pending the development of a programme of works to fully remediate the dangers emerging.
Limited scaffolding was placed at a number of selected points to allow the necessary access for specialists to urgently examine and report on the cause, location and extent of the structural issues, but it became evident that the full extent of works could only be established by erecting a full scaffold. This commenced in January 2015.
The initial scope included:
- Scaffolding
- Repair of the damaged capital
- Examination of the support role of the steel support angle above the capitals and its removal/repair/replacement.
- Repairs to gutter at the base of the dome and provision of safe maintenance access system.
- Examination of the concrete dome, which is now over 90 years old, and preventative passive cathodic protection of part of the reinforcement of the concrete dome.
- Once the scaffold was in place, detailed stone-by-stone analysis began. Meanwhile, the specialist cathodic protection system to the steel reinforcement of the concrete dome was installed.
Examination of the underside concrete surface found traces of the original sky blue decoration, but also found that the reinforcing steel mesh required protection. This involved the application of a new protective coating to the dome along with specialist plaster repairs and replacing the original decoration to this upper dome.
The supporting structure of the Lower Dome (the ceiling to the Round Hall) which is formed by steel trusses with a central opening allowing a view of the Outer Dome above and its plasterwork, again on steel supports, were all meticulously checked to ensure it could take the weight of the stone sections required for an initial replacement of two capitals.
Following detailed temporary works design to ensure that the capitals could be relieved of their loadbearing role without any movement of the overall structures, the intricately carved Portland Stone replacement capitals were carefully hoisted from the floor of the entrance Rotunda and out onto the scaffold. Attached photographs show a damaged capital and new replacement. The steel angle is clearly visible above each. The condition of the removed section of old capitals raised further concerns about how the load from the dome is being transferred though each capital and has led to further structural investigation to ensure the future long-term integrity and safety of the remaining capitals while retaining original historic fabric.
While this analysis was ongoing, additional maintenance and repair work was carried out such as the removal of decayed asphalt weathering details and replacement with lead, thereby allowing more of the original stonework to be again revealed.
Stone indent repairs to the Portland entablature have been completed by skilled stonemasons along the entire circumference of the dome including the removal of iron cramps originally inset into the stone that had caused cracking.
During the removal of the capitals, those that required immediate replacement, it became evident that the capitals were not only damaged at the edges but that the load-bearing core was also damaged.
The next phase of works now being detailed will involve the replacement of a greater number of capitals than originally envisaged, with each capital assessment in itself a separate exercise in removal, inspection and either repair or replacement depending on the structural viability of the stone core.
The steel angle above the capitals will also need to be replaced or repaired.
It is anticipated that this phase of works will be tendered in early 2022 and commence on-site in autumn 2022.
The OPW project team consisting of conservation architects, structural engineers and project administration were assisted by Harrison Goldman Independent Stone Consultants and Punch Consulting Engineers. The advice and related studies on repair mortars and structural analysis by the Graduate School of Professional Engineering Studies in TCD should also be acknowledged.
The total expenditure for the works since commencement in 2015 to the end of this year, are anticipated to amount to € 5.8m with scaffolding costs accounting for nearly one third of this sum.
The Four Courts was constructed between 1776 and 1796. During the 1922 civil war, the building was occupied by Anti-Treaty Forces. The Outer Dome and Inner Dome above the Entrance Rotunda suffered extensive damage as a result of a major fire caused by shelling. The original timber roof and much of the interior and exterior were destroyed. An extensive restoration programme was carried out under the direction of T.J. Byrne, Principal Architect at the Office of Public Works, and completed in 1932.
These work included construction of a reinforced concrete dome to replace the destroyed timber outer dome of the original Gandon building and a steel frame to support the ceiling of the Entrance Hall and the floor above. The restoration also included the replacement of all 24 external columns to the dome with new Portland stone columns. The carved capitals which sat on these columns and supported the roof above were retained however, rotated to present the less weathered faces and repaired with mortar repairs where necessary.
As part of the works in the 1920s a new continuous steel support angle was installed externally around the circumference of the building, but this corroded and was repaired in the 1940s. It was also moved inwards to provide more weathering and a new concrete cover added.