2003:574 - DUBLIN: School Street, Dublin

Additional test excavation was undertaken at the site of a proposed creche and community resource centre at School Street, Dublin 8, in July 2003. The site lies within the perimeter of the medieval abbey of St Thomas the Martyr, which lay a short distance west of the walled town of Dublin.

Initial test excavation undertaken in December 2002 (Excavations 2002, No. 574) uncovered organic silts of probable medieval date which contained timbers, a series of stone walls of post-medieval date and timbers of uncertain date at the base of a geologist’s test-pit. As the site is to be developed, it was necessary to determine the nature and context of the timbers and silts in both areas. Accordingly, the areas of both Trench 2 of the 2002 excavation and of the geologist’s test-pit were reopened in July 2003.

School Street was formerly known as Cryllys Yard and a lane, Gilbert’s Alley, led north along the west side of the site. The best fit of Rocque and the modern OS map indicates that the laneway, Gilbert’s Alley, was moved eastwards between 1756 and 1847. The match of masonry wall foundations uncovered in Trenches 1 and 2 with Rocque’s map is exceptionally good.

School Street has been so termed since at least 1803. The late 18th-century Free School was located on the site of the present school building to the west of the site. The individual dwellings of Rocque’s map had been amalgamated into one large building by 1847. By 1939, the east side of the site was built over by flats or dwellings called Belview Buildings–these had poured concrete foundations, which were uncovered in the excavation.

A trench was dug by machine extending north–south along the central section of the proposed building. The depth to subsoil at the School Street front is 2m below present ground level. The profile consisted of loose red-brick rubble, with a distinctive layer of very soft black silt at the base (c. 0.3m in depth). This silt is either fairly recent in date, or has been considerably contaminated by later activity. There was water ingress at this level. Black stone, east–west running, foundations were encountered—these are 18th-century in date and accord with those on Rocque’s map of 1756. The walls were encountered at less than 1m below present ground level, and the original foundations in all cases extended to subsoil.

Towards the centre of the trench, natural boulder clay was reached at a depth of 1.9m below present ground level. This was overlain by a 0.5m-deep layer of grey/black sulphurous silt, with lenses of brown silt or sod, which contained some fragments of butchered animal bone, twiglets and shell (cockle and other marine). No pottery was recovered. The silt appears to have been deposited by slow-moving water, similar to that at the sides of a river or stream. The absence of red brick or coal indicates that it is 17th-century or earlier in date. The silt was overlain by the stone foundations of the buildings.

Trench 1 measured 2.6m east–west by 2.6m. An ashlar limestone wall, which accords with the east wall of a dwelling on Rocque’s map, extended along the east of the trench. This was encountered just below the tarmac and hardcore of the existing surface. A poured concrete foundation (from Belview Buildings) extended north–south on the west side of the 18th-century wall. Two horizontally laid logs, sawn at both ends, underlay the concrete foundation. These were not of oak. The lower sides of the logs were, however, stained black from the underlying silts. Two fragments of handmade red brick were retrieved from beneath the logs, indicating a date for their deposition no earlier than the 17th century. A single sherd of local medieval pottery was recovered from the underlying black silts. There was considerable water ingress. No further excavation was undertaken.

It seems likely that the logs were laid down by the builders of the limestone wall (in the 18th century) to form a platform or walkway. Water ingress would have been a problem when building the foundations. No further or associated timbers were present.

Trench 2 was located at the north end of the proposed building. There is a complex of limestone walls here, which accords with the building outline on Rocque’s map. The walls were left in situ. The upper level of underlying silts contained fragments of red brick, pan tile, 18th-century pottery and a fragment of very worn two-colour floor tile (medieval). It appears that this material is composed of soils disturbed by the insertion of the masonry foundations. The construction level overlay a black, very pure, silt, which had a strong smell and contained a lot of twiglets. Water ingress occurred at this level. It became evident that the sulphurous black silt is the fill of a gully or channel which extends north-west/south-east across the site. The width of the channel is up to 2.2m, and the depth could not be determined due to water ingress (despite the use of a pump). Finds from the fill include a medieval shoe, both upper and sole, a fragment of a relief floor tile (of indeterminate type) and pieces of handmade brick. Two fragments of ceramic roof tile were also recovered.

It would appear that the channel is a subsidiary which leads eastwards to the main water channel which is known to exist along the eastern perimeter of the site. The presence of this channel explains why the characteristic black silt fill was only uncovered in localised areas in the initial trenching. The purpose of the channel was probably drainage.

Piling and ground reduction was monitored. No intrusion into late medieval material occurred, nor were new features uncovered.

27 Coulson Avenue, Rathgar, Dublin 6