Standing Building Recording
Date 2018
Event ID 1086974
Category Recording
Type Standing Building Recording
Permalink http://canmore.org.uk/event/1086974
NF 77336 50519 A programme of landscape, buildings and materials analysis is being carried out at Castle Borve, Benbecula, within the framework of this project. Surviving upstanding fabric at the castle is evident in three separate fragments of masonry walling and multiple large fragments of ex situ masonry tumble. In general, all of the upstanding fabric has been constructed of lime-bonded rubble-built masonry, with large volumes of constructional peat-fired shell lime mortars visible in continuous core, bedding and coating contexts. Several distinct and contrasting suites of building techniques and/or materials are also evident, however, and these suggest the main castle building is associated with at least three main constructional events, with an additional two subphases relating to a small structure in the south.
The three phases recognised in the main castle building display the following distinct suites of architectural and masonry characteristics: Masonry type A – wide walls; curving and battered wall profiles; informal masonry style without coursing; remarkably course ‘limecrete’ shell-lime constructional mortar; high concentration of window openings. This masonry is concentrated in the W of the surviving building. Masonry type B – very wide walls; straight and vertical wall profiles; moderately formal masonry style including massive rubble blocks and intermittent coursing; shell-lime constructional mortar with well-graded texture; no surviving window openings; rubble quoining but sandstone fragments in core and face contexts. This masonry is concentrated in the E of the surviving building. Masonry type C – narrow masonry walls; formal masonry style with regular through-courses; shell-lime constructional mortar with well-graded texture; sandstone quoining.
Fragments of this masonry are found on both sides of the upstanding building. Buildings analysis at Castle Borve is ongoing and our understanding of the monument is continuing to develop, but various stratigraphic relationships between the distinct constructional phases characterised above are also clearly evident. This includes an abutment in the S wall which suggests masonry type A (in the W) was constructed later than B (in the E). The external wall faces associated with masonry type C walls are also embedded within (and abutted by) the lime-bound core rubble of both main W and E walls of the castle building. In interim, this suggests that the more formally constructed type C fabric is the earliest upstanding masonry on site and should be ascribed to phase 1, that the type B E wall should be ascribed to phase 2, and the type C W wall to phase 3.
A programme of lab-based analysis was subsequently undertaken on material samples removed and collected from Castle Borve. This sample assemblage includes five core mortar fragments, three relict fuel inclusions and two sandstone fragments. Lab-based thin section petrographic analysis of the mortar, sandstone and one relict fuel sample presented further evidence consistent with the characterisation and phasing of the mortars summarised above, and suggested that none of these three main phases could be related to the primary construction of the southern ‘porch’. These analyses also indicated that at least two sandstone types had been used during construction of the building, and these materials are broadly consistent with known outcrops in Morvern and Mull. Archaeobotanical analysis confirmed that two of the probable relict fuel samples were wood-charcoal, further suggesting that the constructional mortar of at least one phase of the surviving building had been manufactured within a mixed fuel (wood/peat) limekiln charge.
Archive: NRHE (intended)Funder: University of Stirling and Historic Environment Scotland
Mark Thacker – University of Stirling (Source: DES Vol 19)
