Heritage sites of Co. Tipperary
Nenagh Courthouse, Banba Street, Nenagh, Co. Tipperary
This impressive building, which dates from 1843, was part of a complex designed by the Dublin architect John Benjamin Keane (d. 1859) that also included the adjacent gaol and wonderful octagonal Governor’s House, now in use as a heritage centre. Keane is thought to have been also responsible for the designs of various other courthouses including those at Ennis, Tullamore and Waterford.
The builders were Denis and John Hanly, a local firm of contractors, who utilised a rather austere dark Calp Limestone from Lisbunny, several kilometres east of the town, for the bulk of this Classical-style building. Contemporary accounts give the price of this stone as being 1 shilling per foot when supplied chiselled at the quarry; another commentator noted that the stone was easy to work. This Mississippian limestone is well-bedded with alternating darker and lighter horizons and penetrated occasionally by thin veins of white calcite.
For the Courthouse it has been dressed into ashlar blocks, which are laid in regular courses on the front façade and display a snecked pattern on the side elevations. The lower story level of the former has channelised rustication of stone blocks with a finely picked surface and drafted margins. This imparts a visual structural strength to the whole front façade; the upper story is of ashlar without rustication. On the side elevations the stone is not as well dressed and has a coarser punched finish but nevertheless is an example of good craftsmanship. The large expanse of grey stone is broken by the insertion of pilasters of the same material.
The Calp Limestone contrasts with the warm yellow to white sandstone from Drumbane, near Thurles, which was used for the solid tetrastyle Ionic portico and pediment as well as the eight steps leading up to the entrance. Each column consists of six drums of similar height. The Drumbane Sandstone is composed of coarse sand grains cemented together with calcite, which would have percolated through the unlithified sands and precipitated in voids between grains. As such this cement is not as strong as the red oxides that bind the Old Red Sandstones, which crop out in Cork and Kerry and elsewhere in Ireland.
The yellow and pale sandstones in Ireland have provided much building stone and while some have been resistant to weathering and decay other units have fared less well. The stone at Drumbane could be quarried in large blocks and scantlings; it was workable in any direction and hence termed a freestone. In a number of the drums, which make up the columns, the sandstone was laid face-bedded; this can be recognized by the vertical orientation of the bedding or layering. This tends to enhance erosion of the stone, which would have been less if laid horizontal to match the original orientation of its deposition. However, often beds are not thick enough in the quarry to yield reasonable lengths for this purpose.
The courtroom inside was rearranged in 1966 and the building underwent considerable conservation in 2004 to 2006 under the direction of Pierce Healy Developments Ltd. In some places the limestone has been patched with replacement stone while some parts of the sandstone columns were rendered in a yellow sandy mortar to match the texture and colouration of the original stone. A new three-story extension was added to be back of the building.
Geology of Co. Tipperary
During the Silurian period (430 million years ago [Ma]) Ireland was divided into two by a narrowing ocean called Iapetus. Muds and some sand were deposited into this ocean and these later made up the mountainous areas of the Silvermines, Devilsbit Mountains to the north and Slievenamon to the southeast. Later, compression caused some of these muds to be turned into slate. By the beginning of Devonian (416 Ma) the Iapetus ocean had closed completely and a large continent had formed, which was thinly vegetated, and through which temporary rivers flowed. Sandstones and coarse conglomerates were deposited and these now form the lofty ridges of Slievenamon and the Galtee and Knockmealdown Mountains.
Following the Devonian the landmass was slowly covered by a shallow ocean that encroached northwards over time. This was warm and supported a huge diversity of living things, which are now found as fossils preserved in the Lower Carboniferous limestone. Later in the Carboniferous the region became land. Sandstones and mudstones, with thin coal seams, were deposited and these now form the low hills of Slieveardagh. The youngest bedrock deposits are found as scattered patches of clay preserved in hollows in the underlying limestone of the Suir valley around Caher (not shown on map). Pollen grains have shown these so-called ‘pipe clays’ to be around 30 Ma – Paleogene. Erosion has taken place during and since the Ice Age and some of the older rocks, such as those of the Silurian, have been revealed peaking out through younger rocks that once covered but now surround them.
Map legend: Geological Map of Limerick (based on GSI 1:1,000,000 map 2003). Pale green: Silurian; Beige: Devonian sandstones and conglomerates; Light blue: Lower Carboniferous limestone; Dark green: Upper Carboniferous shales.