External alterations to include replacement of 8 timber sash windows to reinstate glazing bars.
Our Response

11 Thomas Street forms part of a Grade II 1830 section of three storey terraced dwellings situated within the Bath conservation area and World Heritage Site. It is sited adjacent to the Grade II 1830 Former Thomas Street Chapel, and forms part of the largely Grade II 1830 Thomas Street running up to meet the Grade II early 19th century terrace at Lyndhurst Place. 11 Thomas Street is located on the east side which is bisected towards Lyndhurst Place with the insertion of a section of later 19th or turn of the 20th century terraced housing of a distinctly different elevational treatment and scale. Nonetheless, in wider views the street is defined by its regular, stepped articulation down the eastern slope to meet London Road, at which point the buildings on the junction have wider elevations with a larger number of bays. The Former Thomas Street Chapel remains the focal visual point in scale, detailing, and architectural contrast with the rest of the terrace. There have been later alterations made to individual buildings within the terrace which have interrupted their grouped aesthetic and architectural uniformity such as the painting of the principal facades, and the replacement of their original 6-over-6 sash windows with later Victorian single pane sashes.

In the light of the declared Climate Emergency BPT is generally supportive of retrofit measures that protect elements that contribute to the special architectural and historic interest of a listed building; alterations are expected to be visually coherent with the character of the building, and the wider shared character of the listed terrace and surrounding conservation area.

The existing windows are indicated to be Victorian, and therefore have some limited historic significance with regards to the age of the fabric. However, we note that these were not original to the intended design of the building. The proposed replacement of the existing windows with a return to windows of a multi-pane Georgian fenestration would therefore reinstate part of the original historic appearance of the building and its special historic and architectural interest, and constitute a conservation gain.

Where the principle of window replacement in a listed building is considered acceptable, this offers a positive opportunity for the implementation of energy-efficient retrofits without the loss of historic fabric.

We are supportive of the principle of the use of slimlite glazing in this setting, dependent on the use of quality detailing appropriate to the appearance of a listed building and the wider group value of the terrace. This can be achieved through the use of an appropriate style of glazing bar thickness and profile to ensure the timber frame isn’t overly heavy or blocky in appearance.

We strongly recommend that further information is provided regarding the proposed glazing bar thickness to ensure this would be compatible with the fine fenestration present along the wider terrace. We additionally note that there are several other examples of slimlite double glazing installation along the street at 3 and 7 Thomas Street (as noted in the D&A Statement); these appear to use a different glazing bar profile, potentially an ovolo or lamb’s tongue profile, than that currently being proposed here. The proposed works offer a positive opportunity to reinstate some of the architectural symmetry and regularity along the terrace as originally designed; we therefore suggest that further consideration is given to the selection of a glazing bar profile in keeping with the profile type seen along the street.

This proposal, if got right, could help provide an invaluable opportunity to monitor the thermal and acoustic efficiency of the windows, before and after, whilst also observing any additional repercussions such as changes in humidity levels. This information could then be used to more accurately assess the suitability of slimlite installation in Bath’s historic building stock.

BPT is very interested in working with the applicant to reach an acceptable solution and getting better understanding of the existing window condition and design.

Application Number: 21/04875/LBA
Application Date: 29/10/2021
Closing Date: 26/11/2021
Address: 11 Thomas Street, Walcot, Bath
Our Submission Status: Comment