2003:2156 - SEAPOINT, Dublin

Seapoint Martello Tower has been acquired by the Genealogical Society of Ireland, who have renovated the tower for the purposes of having a permanent home for their archives. As part of the renovations it was necessary to remove an existing concrete floor in the ground floor of the tower and reduce the internal floor level further in order to construct a new floor level. During monitoring of this ground reduction, the original stone floor of the tower and the foundations of internal dividing walls were revealed.

Though the overall plan of the tower is circular, the interior has two straight end walls and two curving side walls. The ground floor measures 6.05m north-north-west/south-south-east by 6.2m. Before works began the floor surface consisted of a shallow layer of low-grade concrete, only 30mm thick.

Beneath the concrete floor was a layer of redeposited rubble, averaging 0.2m deep, that had been used to create a level surface before the laying of the concrete floor itself. This layer sealed the original granite slab floor below and the foundations of the internal dividing walls. Both the internal brick walls and sections of the granite floor had been robbed at some unknown date. It seems probable that the redeposited rubble layer and concrete floor above were introduced shortly after the removal of the walls and floor slabs. Curiously, while some 20th-century iron objects were noted in the rubble layer, the absence of any plastic objects would suggest that this phase took place at some time before the 1960s.

The original floor survived best in the eastern half of the ground floor. The floor slabs range from 0.36 to 0.62m wide and 0.78 to 1.28m long. On average, these slabs are 0.12m thick. They are rectangular in shape, except where they had been specifically cut to fit against the curved eastern and western side walls of the tower. The slabs are very tightly fitted and well bonded. They were laid in a longitudinal fashion, roughly east–west, with the narrower slabs placed at the northern and southern ends of the ground floor. Towards the centre, wider slabs were laid in a similar longitudinal manner. However, near the fireplace, set into the eastern wall, the orientation of the slabs was changed to roughly north–south. This would seem to indicate that the floor was originally laid at the northern and southern ends towards the centre of the floor area.

The floor slabs had been robbed elsewhere, except for a few surviving against the tower wall in the north-western quadrant of the ground floor. No floor slabs survived in the south-western quadrant. It was evident here and elsewhere that the floor slabs had been laid directly onto a solid mortared surface mixed with some stones of various sizes. In the south-western quadrant, this surface was about 0.1m lower than the level of the corresponding surfaces exposed elsewhere. It is not clear if this was an intended level in this area or if an upper layer had been removed as a result of the floor slabs having been removed so completely in this area. This surface was not penetrated during the works, though it appears that it may have been laid directly onto the underlying granite bedrock.

The foundation of a roughly north–south wall was revealed which originally supported a brick wall dividing the ground floor into two roughly equal parts. The foundations of a further wall, aligned roughly east–west, were also revealed, and this would originally have divided the western half of the basement into two equal quarters. These walls would originally have supported the timber floor of the first floor above. Both walls were demolished, probably about the time that many of the floor slabs were taken. The wall foundations consist of a foundation plinth and the lowermost course of the brick wall. The brick was laid transversely to the foundation course of the main north–south wall and longitudinally on the east–west wall. The upper surface of this lowermost course of brick was flush with the upper surface of the floor slabs, where they survived contiguously.

The lowermost course of the brick wall did not survive continuously along the main north–south wall and, where it did not survive, the underlying foundation plinth was exposed. At the northern end this consisted of a solid foundation plinth of mortar and stone, whereas at the southern end several large, uncut slabs had been laid down as the upper surface of the foundations. It seems possible that these slabs were laid at this point deliberately in order to support a threshold slab of a door between the main room and the small room occupying the south-western quadrant of the ground floor. Curiously, there was no evidence for a break in the short east–west dividing wall to indicate the location of a door within this wall, which would have been necessary for access between the two small rooms.

The granite floor slabs and dividing wall foundations have been preserved as part of the renovation works at the tower. The lowermost course of bricks of the dividing walls had to be removed in order to lay the new floor contiguously with the surviving granite floor slabs. However, the wall plinths have been preserved underneath this new floor surface, which consists of gravel and hydraulic lime (2:1).

Department of the Environment, Heritage and Local Government, Dún Scéine, Harcourt Lane, Dublin 2