2004:1230 - DUNBOYNE: Dunboyne Castle, Castlefarm, Meath

Dunboyne Castle is an 18th-century house cut off from the village of Dunboyne by the Castle River, a tributary of the River Tolka. The house with its 87-acre demesne is at the time of writing being developed for mixed residential/commercial use. Planning permission has been approved for 564 units of housing/apartments and for the extension and conversion of the existing building to a hotel and leisure complex.

Pre-development testing was carried out at the site by Stephen Johnston in November 2001 (01E0875). A number of archaeological features came to light at that time and further investigation was advised. Because of its proximity to the 18th-century house, and the fact that it was partly covered by two 20th-century wings, the medieval ditch was not recorded during testing. A condition of the planning permission stipulated that monitoring of groundworks should be undertaken. This licence relates to monitoring, excavating and recording of archaeological features in the vicinity of the house and to pre-development testing in the fields to the south and east. The landscaped gardens north of the house are being retained. The work was carried out over a period of twelve weeks, commencing on 22 July 2004. The licence was subsequently extended for a further three weeks, commencing on 8 December 2004, to monitor underpinning of the basement walls of the 18th-century house and lowering of the basement floor. During the first two weeks of September 2004, a licensed metal detector survey (No. 1231, Excavations 2004, 04R143) was also carried out at the site. The survey focused on spoil excavated from the medieval enclosure ditch.

The medieval enclosure was evidenced by a massive ditch, of which only the southern half fell within the area being developed. In all, a 72m arc of the perimeter of the ditch was revealed and mapped. Moving clockwise from the west, the ditch survived as follows. The west sector was deeply truncated by an 18th- or early 19th-century vaulted cellar and was further disturbed by the construction of a 20th-century 'west wing'. At the south, part of the rear (southern) elevation of the 18th-century house was built over the inner edge of the ditch. At the southeast, the line of the ditch ran under the house foundations to emerge again near the north-east gable. Because of the proximity of the house and ditch, and indeed the scale of the ditch, safety factors more or less determined the level to which the archaeology could be investigated. A full cross-section of the ditch was excavated at the south-west using both manual and mechanical means. The fill from the adjoining southern sector was removed mechanically. The demolition and cleaning out of a sunken basement that ran along the rear elevation of the house also revealed part sections of the ditch. At the south-east and east, and at basement level within the house, the line of the ditch was recorded and some ditch fill was removed during underpinning works.

The full width of the ditch was exposed only at the south-south-west; its maximum dimensions were 8m wide by 4.5m deep. The west and south portions were cut through hard yellow boulder clays and the underlying calp limestone rock of the area. The eastern sector was not emptied out, but, along some of its length at least, it appears to have been cut through softer, siltier clays. The land slopes down gently from west to east. The absence of a basement level in the north-west quadrant of the house may be due to high levels of bedrock. In contrast the eastern area would have lain within the flood-plain of the Castle River. There was evidence to indicate that upcast was spread over the area immediately outside the ditch in the east sector. This may have been done to maintain a uniform depth and/or to prevent erosion of the ditch by floodwaters.

The ditch was U-shaped in section, with very steep sides that are nearly vertical in places. The break of slope is very sharp - almost a right angle - at the outer lip and is only slightly more gradual on the inner edge. No trace of any entrance feature was noted in the area investigated. The line of the unexcavated northern sector of the ditch is masked by later landscaping and there are no topographic clues as to where exactly an entrance might have been located.

The fill of the ditch can be broadly divided into three 'spits': lower, middle and upper. The lower and middle were segregated largely on the basis of water content and differential preservation of organic remains. Where the ditch was fully emptied at the south-south-west, the lower spit was made up of waterlogged black or dark-brown silty deposits. Some food refuse (mainly animal bones and oyster shells) was recovered at this level but not in any greatquantity. Worked and unworked timbers and brushwood were plentiful and appeared to have been thrown into the ditch while it was still empty. The worked timbers included thinly split planks, wooden pegs, a possible shingle or paddle fragment, stave fragments and parts of at least two wooden bowls. Post-excavation analysis is ongoing, but it appears likely that the planks and pegs derive from one or more structures that were located in the interior of the site. There is evidence to suggest that the structures were deliberately destroyed, although the absence of any very substantial timbers suggests that some elements may have been salvaged and recycled.

The bulk of the middle fill was made up of dried-out and compacted silty deposits. Organic remains were limited to fairly dispersed remains of food refuse. Analysis of the relatively small pottery assemblage is not yet completed but 12th/13th-century cooking wares predominate. A localised dump of small-stone rubble occurred in the southwest sector of the ditch. The stones had been thrown in from the exterior but were too low down in the ditch to have been used as a dry causeway.

The upper fill was similar in make-up to the middle spit, but there was a noticeable decrease in pottery finds. There was also evidence for later intrusive activity in the form of trenches, pits, wells and drains and some chronological mixing of finds is possible.

Only a very small proportion of what would have been the interior of the medieval enclosure was available for excavation. The 18th-century house occupies roughly a third of the enclosed area. Monitoring of the lowering of the basement floor of the house showed that the basement had been cut down into undisturbed natural clays. Underpinning of one of the interior dividing walls also exposed a 'high spot' of bedrock. The only other part of the enclosure that could be examined was a 4m-wide strip of ground lying between the west gable of the house and the subterranean cellar. This area had been disturbed by the construction of the 20th-century west wing. Intermittent traces of a deposit of dark soil were recorded between intrusive modern features, but no dating evidence was forthcoming.

It remains unclear whether the site was a motte, a ringwork or some other class of enclosure. The primary ditch fill seems to have accumulated within a relatively short period and, at this stage of the post-excavation analysis, the evidence suggests that the ditch went out of use at some time during the 13th century. It is planned to submit some of the timbers for dendrochronological dating.

By the later medieval period (i.e. the 15th/16th centuries), if not a century or two earlier, the line of the ditch was probably marked by only a slight hollow, averaging around 0.5m in depth. Only a few sherds of later medieval pottery were recovered on the site and all of these came from secondary contexts. The absence of any very definite evidence for later medieval activity was surprising, as there is historical reference to the proposed building of a castle at Dunboyne in the 16th century. The 17th-century Down Survey map of the area also shows a fairly substantial building standing more or less on the site of the present house. It is possible that traces of these structures still survive in the unexcavated area to the north of the house, but only a very small number of finds from the site fall into the period 1300–1700. These include a late 17th-century silver penny found at the interface between the backfilled ditch and 18th-century level-raising material.

The post-medieval features recorded at the site include a large mid-18th-century ha-ha and later 18th- and 19th-century features such as cobbled yards, wells, culverts and a subterranean vaulted cellar.

Unit 4, Dundrum Business Park, Dublin 14