At a Development Control meeting tonight a recommendation to remove the decorative lime plaster floors in Bridgford Hall and replace with softwood will be voted upon.
- Bridgford Hall is a Grade II Listed Building which is owned by Rushcliffe Borough Council. The Hall was built between 1768 and 1774 by Mundy Musters, Lord of the Manor of West Bridgford.
- It has had numerous extensions which were added in the late 19th and mid-20th century. The main hall is 2 and 3 storey having single storey elements at either end. It is constructed in red brick with parts of the building having a mix of pitched and flat roofs with clay tile and slate finishes.
- The building has unequal bays and has a door that contains stained glass with West Bridgford U.D.C letters in it. To the left of the main building there are gabled outbuildings and a 3 storey addition having regular fenestration. The main frontage has a central flight of 3 steps with handrails.
- To the right there is a 2 storey flat roofed addition with external fire escape stair and beyond a flat roofed former billiard room (more recently used for wedding ceremonies). Internally the main stair terminates at the first floor landing. Access to the remainder of the building is via a secondary staircase which has a dogleg with intermediate landings to span the different floor levels.
The Hall Bridgford Road West Bridgford Nottinghamshire
- (i) 15/03012/LBC – Removal of lime plaster floors of the second floor of the Georgian section of Bridgford Hall to enable the floor construction to be upgraded to provide fire and acoustic separation between residential units, and replacement with softwood floor. Dry lining to 2 number outbuildings on the ground floor.
- (ii) 15/03018/VAR – Variation of condition 8 of 15/1169/LBC to allow additional suspended ceilings; and removal of existing ceilings in rooms GF01; FF01 & FF25, and replace them with plasterboard.
- (iii) 15/03019/VAR – Variation of condition 21 of 15/1168/FUL to allow additional suspended ceilings; and removal of existing ceilings in rooms GF01; FF01 & FF25, and replace them with plasterboard.
Conservation officer comments:
- The floors have been identified in 6no. rooms in the oldest part of the hall on the 2nd floor. The rooms below have decorative plaster ceilings, and in 3 cases these ceilings are especially fine, being the best examples within the property. In the remaining 3 cases the rooms beneath all have surviving cornices in good condition and of reasonable elegance and quality. These features are considered important parts of the formal decorative scheme of the property and a key component of the special architectural character of the hall.
- I have seen the floors and note that none is in perfect condition. All have been covered in a thin surfacing screed which appears to be gypsum based (judging by its colour), this has hidden the surface texture and detail of the floor surface beneath. The screed material is well bound to the floor surface and is not readily removed, the floor surface below is powdery and pitted and does not exhibit a smooth or polished surface sometimes encountered with these floors. Whether this was a defect and the reason the screed was applied, the intended surface finish, or whether the floor surface was abraded to provide a positive key for the screed mix is unclear. Beyond this several large cracks are present, visible through the screed, in each of the 6 rooms. The fact that the screed too is cracked suggests either some continual movement (possibly seasonal) or alternatively that the support structure flexes to a notable extent under loading.
- The cracks, in most cases, are not linear and do not appear to follow joists or beams which form the floor structure, instead the cracks form arcs across the floor and clearly relate to something other than simple sub-structure issues. The cracks are not insubstantial, and in the case of room SF03 cracks are in the region of 8mm wide in places.
- I appreciate and understand the wider issues in relation to this proposal. There is a requirement to provide fire separation between floors, a factor which would exist for almost any new use to which the building could be put. In this case the ceilings below cannot be upgraded or replaced as they have high historic and architectural significance such that every effort must be made to retain them. Equally a suspended ceiling solution for these areas would be undesirable, although it would enable the historic decorative ceilings to be retained, and it could even be argued that such a suspended ceiling would ‘protect’ them their value as architectural embellishment is lost if they are hidden from view. Their entire function, and thus a substantial element of their significance and their contribution to an understanding of the wider significance of the building, rests on being able to see and appreciate these ceilings within the context of their rooms. It is my understanding that upgrading from above, laid atop existing floor finishes is not viable as it fails to provide fire protection to the structural elements of the floor. As such although such upgrading might prevent spread of fire into a room it would not necessarily prevent collapse of that floor within the defined fire protection period.
- The previous ‘best solution’ was the introduction of fire protection into the cavity of the floor-voids from above. Given the high significance of the ceilings of the rooms below this does appear to continue to be the best solution to the requirement to introduce fire protection into the building. Unfortunately, the only realistic prospect of installing such material into the floor cavity with the least impact on historic fabric and significance would be from above, resulting in the loss of the plaster floors. Given that these are not in good condition, and given the difficulty of both removing the modern surface screed and its potential masking of less significant patterns of cracking, this does appear to be a justified approach, especially given the fact that structural engineers are typically reluctant to sign off on floors of this nature where the construction is an unknown quantity and the degree of deterioration is disguised by subsequent interventions (the screed).
- Although plaster floors were historically regarded to offer good fire resistance this property is ultimately dependant upon them being in good condition,
cracks and defects, such as these floors exhibit, can significantly reduce their ability to withstand and resist fire and the spread of fire. In addition to this the fact remains that the plaster floor sits above its support structure and thus offers protection from the spread of fire, but does not necessarily provide protection to prevent structural failure as a result of fire.
- The existing floor is around 50mm thick (exactly midway in the typical range of 25-75mm for floors of this type) and laid on straw. This is the more common construction detail for these floors and is far more common than alternatives such as closely spaced timber boards which would have been indicative of a more unusual, and importantly more significant, floor construction. In this respect there is nothing particularly unusual, or indeed special, about these particular floors.
- Beyond this the application proposes that the floor then be reinstated as a suspended timber floor rather than a solid plaster floor. The majority of cases of which I am aware where limeash, plaster and gypsum plaster floors have been reinstated in buildings are either buildings in the hands of bodies like the National Trust/English Heritage, solid ground floor floors (which are of fundamentally different character and construction to suspended solid plaster floors) or floors which do not have ceilings of high significance beneath them. As such in these particular circumstances where the building is to be in an active commercial use the desirability of having access to the floor void for future maintenance and servicing, given that such future access for maintenance cannot be achieved from beneath, the argument that a timber floor would therefore be more desirable is appreciated and accepted.
- More significantly creation of a new plaster floor would not simply be a replica at best but would also be a non-matching replica. Whilst there is reasonable amounts of documentary evidence relating to slid lime ash floors used in ground floor situations there is, by contrast, a paucity of contemporary evidence of the methods and materials used in the construction of these floors. It is generally accepted that the binder utilised was, at best, equivalent of a modestly hydraulic lime, or if the binder was gypsum based (given the proximity of the gypsum belt which brushes the southern Nottinghamshire border) then ‘somewhat’ harder than plaster or Paris.
- Unfortunately the assumptions of gypsum based mixes in literature cannot be confirmed. It is assumed that gypsum mixes contained some proportion of anhydrous or hemi-hydrated gypsum, unfortunately when water is added to these materials they are re-hydrated and they cannot therefore be differentiated from each other through chemical analysis of a finished floor.
- Equally the more readily known properties (through analysis) of lime based mixes is difficult to replicate. The material tended to contain residue from the kiln as the lime used tended to be the residue from the kiln bottom. The mix of contaminates might be identifiable through analysis, but might not be possible to incorporate into a replacement mix if any of the material would compromise the mix or contravene modern health and safety requirements.
- A pragmatic approach employed in some cases has been the grinding up of the existing floor so that the historic floor itself is added to the new mix as part of the aggregate. Unfortunately the specifications for these mixes almost always seek the use of modern NHL2 or 3.5 naturally hydraulic limes.
Although these are a ‘known quantity’ which a structural engineer can use to determine acceptable loadings from a safety perspective they are both stronger and materially different from the moderately hydraulic limes likely to have been used in the original construction. Indeed even publications such as the recent Practical Building Conservation series promote replacement floors being designed “to meet desired aesthetic and performance requirements; the modern requirements of a mortar floor may be very different to those of the past”. If it is accepted that even best practice and up-to-date literature on the subject advocates a replacement with a different composition in order to meet modern requirements, then I see no reason why, if the modern requirement includes a requirement for access, that the replacement with a suspended timber floor cannot be considered to be a reasonable approach.
- Solid plaster floors do have historic significance, and to an extent they do form part of the social hierarchy reflected in the fabric of the building (however it must be accepted that such floors are known to have been used in high status rooms of other properties on the basis that they have properties of warmth, exclusion of draughts, sound proofing, aesthetic character and durability which are in some ways desirable). That being said within the circumstances, given the condition of the floors, the necessity and justification of the work, together with the lack of practically achievable alternatives which would not cause greater harm to the special architectural or historic significance of the building I conclude that the harm caused would be less than substantial, would benefit from a clear and convincing justification (Paragraph 132) and would be necessary in order to bring about the beneficial and desirable sustainable re- use of the listed building.
- Although the presence of any harm would fail to secure the ‘preservation’ of the listed building; as considered ‘desirable’ within section 16 of the Planning (Listed Buildings and Conservation Areas) Act 1990 I do feel that there are valid benefits to the wider community and to the future sustainability of the building, which could be delivered as a result of this proposal and its associated schemes. It is possible for you, as decision maker, to conclude that the benefits which this proposal secures, including a viable long-term use for the listed building, would outweigh the presumption against granting planning permission under section 16 of The Act, but in doing so you must be mindful of the relevant status and significance of the statutory weight of The Act as legislation and of the weight afforded to the NPPF as policy, specifically the paragraph covering the assessment and balancing of less than substantial harm within paragraph 134.
- The proposal also details the introduction of some internal lining to external walls at the southwest end of the building, within the lower status ancillary buildings which are to be converted into habitable rooms. These walls have no internal wall linings or coverings at present (besides paint applied to brick surfaces). Whilst there is an exemption from compliance with Part L of the building regulations where compliance would result in harm to the special architectural and historic character of a listed building (and this is an exemption which has been utilised for other elements of work as approved at Bridgford Hall, including works to windows) in this case the desirability of improving thermal performance wherever practicable does not result in an undesirable impact on the architectural and historic significance of the building, and the method specified would ultimately be reversible.