Basement Flat, 16 Norfolk Crescent, Kingsmead, Bath
16 Norfolk Crescent forms part of a Grade II* listed early 19th century terraced crescent of townhouses, a number of which have since been internally sub-divided into apartments, situated within the Bath City-Wide Conservation Area and World Heritage Site. Loosely attributed to John Palmer, and indicated to have been completed by John Pinch post-1810, the crescent is indicative of speculative Georgian development, and the use of a homogenous, monumental form characteristic of Bath’s larger scale terraces and crescents, and as such clearly contributes to the Georgian town planning and architecture OUV of the World Heritage Site. Part of No. 16’s special interest is attributed to its group value within the wider terrace and its reinforcement of the crescent’s symmetry and uniformity, with a shared Bath stone ashlar principal façade, rusticated ground floor, and consistent detailing such as the addition of wrought iron balconies at first floor level.
BPT supports works for the reinstatement of sash windows at lower ground floor level where this would be in keeping with the appearance and character of the wider terrace. As existing, the terrace features some variation in window size, with basement windows generally utilising a 6-over-6 form to match the ground floor, although the application makes reference to the existing 8-over-8 sash window at No. 15 as a design reference. As part of proposals, it would be useful to provide further information regarding the historic window openings at No. 16 to indicate whether the proposals would be a reinstatement of the original windows, or instead a modern replication of neighbouring examples.
Where the proposed replacement windows would be positioned below street level and would be less visible, this could be a positive opportunity for the use of slimlite double glazing with no loss of historic windows and limited impact to the appearance of a listed building. This would remain dependent on the proposed glazing thickness and further details as to window profile and glazing bar thickness to ensure an appropriate appearance and finish.
Whilst BPT does not typically comment on internal works without the benefit of a site visit, we have some questions regarding the treatment of the bathroom at basement level, which is indicated to currently be suffering from water ingress attributed to “a combination of a leaking shower and timber panelling within the Bathroom.” We support works to address ongoing water damage, including the removal of the timber panelling and the affected plaster beneath, but we have some concerns about the proposed use of a “Koster restoration plaster”, to be applied to the exposed walls. The Koster safety data sheet indicates that the material specification includes Portland cement; the system is further categorised as a “NBS Specification J10 Cementitious Mortar Tanking/Damp Proofing system” by Delta Membranes.
We therefore have strong heritage concerns regarding the use of a cementitious damp proofing system, because of its incompatibility with the natural porous qualities of traditional materials such as Bath stone. BPT opposes the use of cementitious tanking in listed buildings where this would prevent historic fabric from being able to ‘breathe’. Cement-based damp proofing systems are frequently prone to failure and can exacerbate existing damp conditions whilst being incredibly difficult to remove/reverse. There is insufficient justification for damp-proofing interventions where the source of water ingress will be addressed as part of proposals. We therefore strongly recommend the use of more sympathetic measures to mitigate the effects of damp such as the application of a limewash or lime plaster of an appropriate sample and finish.
The proposed damp proofing would result in inappropriate material alterations and harm the heritage significance of a historic building without adequate justification contrary to the Planning (Listed Buildings and Conservation Areas), Section 16 of the NPPF, and Polices B1, BD1, B4 CP6, D1, D2, D3, and HE1 of the Core Strategy and Placemaking Plan and should therefore be refused or withdrawn.