Event/Activity EPM297 - Archaeological works at the Square Tower, Old Portsmouth

West Sussex Archaeology carried out archaeological monitoring during works to repair a section of flooring in the north-east half of the ground floor of the Square Tower. Archaeological work was carried out as a condition of Scheduled Monument Consent and monitoring took place on the 8th, 9th and 11th January 2024. The repair work involved the lifting of a section of modern vinyl flooring which sat on top of earlier floorboards. The floorboards were then lifted to expose the joists beneath. This section of oak floorboards and underlying joists had been left in situ after restoration work was completed at the Square Tower in the early 1980s. Archaeological analysis carried out during the 1980s restoration concluded that the spine wall dividing the ground and first floors and the brick barrel vaults above had been inserted as one episode in c.1779 when the tower was converted into a victualling store, and that first floor timbers in the north-eastern half of the building and the infilling of the basement dated to the same phase of works. However, the floor joists on the ground floor were thought to have dated to the 19th century with re-used 18th century floorboards above. During the 2024 monitoring works further analysis and recording of the ground floor floorboards and joists took place. This included making a photographic record of the original floorboards. Dendrochronological analysis was also carried out on ground and first floor timbers in order to try and date the floors. The timbers exposed by the work on the ground floor were considered to be of extremely low dendrochronological potential and only one sample was taken from the most promising floorboard in this area. Nine core samples were taken from the first-floor timbers above where the dendrochronological potential was thought to be high. The archaeological monitoring in 2024 showed that the ground floor floorboards and joists were originally installed as part of the programme of alterations carried out in the 18th century which saw the insertion of the brick spine wall and new floors within the building. A dendrochronology date obtained from first floor timbers indicates that these works were carried out shortly after 1735, and not in 1779, as previously thought. It was the original intention to re-lay the floorboards once the repairs had been completed. However, this was not possible due to the poor condition of the boards and they have therefore been replaced with the exception of one floorboard which has been left in-situ as it is fixed underneath a steel and glass barrier around the exposed basement area. The original ground floor floorboards are now held within the collections of Portsmouth Museum Service. Museum Accession No: 2024/17