Ministerial guidelines
Architectural Heritage Protection: Guidelines for Planning Authorities
Protected structures, architectural conservation areas, curtilage, and works to historic buildings.
Department of Arts, Heritage and the Gaeltacht · 2011 · 267 pages
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- Architectural Heritage Protection Guidelines for Planning Authorities 169 CHAPTER 10 OPENINGS Doors and Windows 10.7.4 Internal secondary glazing may be considered acceptable where the installation can be reversed without damage to elements of the historic fabric of the building, such as panelled shutters and the like. Secondary glazing can provide some thermal insulation and is usually a more effective means of providing sound insulation than double-glazing. A method should be designed to allow for the use of internal shutters where these exist. It should be borne in mind that there may be the possibility of unacceptable reflections from the secondary glazing when viewed externally. This may affect not only the character of a protected structure but also have an adverse effect on the character of an ACA. Sealing measures generally 10.7.5 The fabric of older buildings was generally designed to allow for the absorption of moisture from the ground or from rainwater and its subsequent evaporation from the surface or through the natural ventilation of the interior of the building from open fireplaces or unsealed windows and doors. Measures to seal an older building can result in moisture being trapped within the building or within its fabric. This can lead to damage of the fabric and finishes of the building by condensation or by promoting fungal attack. For this reason, the proposed insertion of sealed units such as uPVC windows and doors into a historic building, even where the original elements have previously been lost, should be treated with great caution. A draught-proofed window should not be visibly altered by the work, except on close inspection, as the patented strips inevitably make a small difference. It should be borne in mind that in most cases the brush or pile-edged parting bead is of white plastic, which limits the colours the sash window can be painted without making it unduly visible. The work should also be finished off well, retouching any disturbed paintwork, but the pile or brushes must not be over-painted as this could render them ineffective Well-designed and fitted secondary glazing will provide a measure of both heat and sound insulation while allowing the historic window to remain intact. Two main aspects of the design should be carefully considered so as to limit both the aesthetic and physical impacts: the visual effect of the proposed glazing (this example is visually obtrusive from both the street and the interior of the building) and the means of fixing. Internal window shutters should not be disabled by the works and the glazing should be removable without damage to the historic fabric
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- Architectural Heritage Protection Guidelines for Planning Authorities 171 CHAPTER 11 INTERIORS 11.1 Introduction 11.1.1 The interior of any protected structure is of primary importance. Although the interiors of many protected structures are not accessible to the general public, they may nonetheless be essential to the character and special interest of that building and are therefore protected. 11.1.2 Protection extends to all features of quality and interest in the interior of a protected structure, not only to those features which are original. In making an assessment of the interior of a protected structure, a planning authority should obtain all necessary expert and specialist advice. This assessment should ideally be carried out on a roomby-room basis. Consideration should be given, in each room or space, to elements such as the floor, ceiling and walls and any interesting features or fittings present. An overall assessment of the interior and the interrelationship of different spaces should also be made. 11.1.3 Items to consider in the assessment of an interior include: a) Does the structure retain its original plan-form? b) If not, are there any alterations or additions of interest? c) Have the proportions of the rooms or spaces been altered? Have they been damaged by alteration, improved or merely changed? d) Are there any interesting, planned relationships between rooms or spaces, such as enfilades, processional routes, industrial processes and the like? Have these been altered or interrupted by changes or created out of previously existing spaces? e) Is there a hierarchy to the various spaces? How do the principal spaces relate to the subsidiary ones; for example, dining rooms to kitchens or banking halls to offices? f ) Is the relationship of the spaces or the layout of rooms of interest because of the insight it gives into the workings of a bygone time; for example, the relationship of cells to a courtroom or a milling room to a store? The interior of a protected structure is of primary importance to its character. Ideally, the special interest of the interior should be assessed when initially protecting the structure, but failing that, it should be evaluated when proposals are put forward to redevelop the structure. The importance of an interior is not confined to decorative features: the plan form or the structural system itself may be innovative, as in this early multi-storey, steel-framed store house
- CHAPTER 11 INTERIORS Architectural Heritage Protection Guidelines for Planning Authorities 172 Whereas an important fixture of this interior was retained in the gallery of this former church; the original plastering, floor and other fixtures have all been lost. Even if an accurate reproduction of the missing features and decoration were to be undertaken, the result would largely be a new interior The arrangement and inter-relationship of rooms and circulation spaces in an interior – here a top-lit long gallery in a large house – are key to how the building was designed to work and to be experienced. Proposals to change the plan form and alter or introduce new circulation routes should therefore be closely scrutinised g) Are there elements of interest in the interior such as early iron and concrete floors, timber stud partitions, lath-and-plaster ceilings, exposed roof trusses? h) Is there any joinery of quality such as internal doors, window shutters, skirting boards, dado rails, architraves, wall panelling? i) Are there finishes of interest to flooring, walls or ceilings? j) Are there any surviving original or good quality decorative schemes? These might include limewash, paint, wallpaper, wall-paintings, painted ceilings, tiling, gilding, and other finishes. k) Are there any fixtures or features which are original to the building or of architectural or historical interest; for example fireplaces, counters or benching? l) Is there surviving machinery connected with a building’s present or former use, such as milling machinery, early lifts or dumb waiters? 11.1.4 Where features are considered to be worthy of protection, they should ideally be retained in situ. Even where elements or features are decayed or damaged, they should be repaired rather than replaced. Repairs and alterations should be carried out in a manner appropriate to the individual element or structure and preferably in a manner that is readily reversible. 11.2 Elements of the Interior Plan-form IDENTIFYING SPECIAL FEATURES FOR PROTECTION 11.2.1 The plan-form of a building is one of its most important characteristics. Where the original planform remains, or is readily discernible, it should be identified and respected. Later alterations of definite architectural merit should also be identified for protection. CONSIDERATION OF PROPOSALS AFFECTING PLAN-FORM 11.2.2 Where alterations are essential for the continued viability of a building with an interior of value, attempts should be made to keep works to a minimum and preferably confined to areas of secondary importance. For example, where existing internal doorways are to become redundant, as a result of alterations to a structure, the doors should be retained in position and simply locked shut, rather than stripped out and the opening blocked up.
- Architectural Heritage Protection Guidelines for Planning Authorities 173 CHAPTER 11 INTERIORS 11.2.3 Wherever possible, the alterations should not change the interrelationships or the proportions of prominent spaces such as entrances, staircases or principal rooms. In a protected structure that retains its original spatial layout, proposals to subdivide the building into several smaller units or to open up a pair or series of rooms to create a larger space should be permitted only in exceptional circumstances after very careful scrutiny by the planning authority. 11.2.4 Where an earlier, unsatisfactory subdivision or opening up of rooms or spaces has taken place, in a manner which has distorted the original design, the opportunity could be taken to reinstate the earlier plan-form. Such inappropriate alterations could include the subdivision of principal rooms to form smaller rooms, lobbies or corridors, the addition of partitions which divide or obscure windows or obstruct designed circulation patterns. 11.2.5 Reinstatement work, such as the removal of later partitions or lobbies, should generally be undertaken where it can be readily achieved and does not involve the loss or damage of later alterations of quality. Floors 11.2.6 All floor structures of interest, which could include structural members such as timber, iron or steel beams, trusses, joists and brackets and floor finishes or surfaces of interest, should be identified and respected, whether or not they are original. Finishes could include marble or stone paving, timber boarding or blocks, scagliola, tiles, cobbling, brick, rammed earth, lime ash, plaster, terrazzo, or early concrete. 11.2.7 Efforts should be made to retain these floor types and any others of interest. Associated architectural details such as cast-iron floor grilles should generally be conserved even where they have become redundant. CONSIDERATION OF PROPOSALS AFFECTING FLOORS 11.2.8 Where historic flooring exists, due care should be taken when works are undertaken for the installation or repair of services or the installation of thermal or acoustic insulation or for fire-safety enhancement works. Many types of floor finish are easily damaged and difficult to re-lay and should not be disturbed without good reason. Where a floor of particular interest or merit exists, an alternative service route should be found in order to avoid the disturbance of the floor. For example, this may be the case where a previously undisturbed The practice of the recent past of subdividing large rooms by forming boxed cubicles within the space has only one advantage: it makes their removal less complicated and damaging than if the partitions extended up to the ceiling. However, the reversibility of this type of work may not always justify the insertion of new partitions into high-quality architectural interiors Taking up and relaying stone flags to accommodate underfloor heating and other services is delicate work which has the potential to cause irreparable damage if incorrectly or clumsily done. The use of skilled personnel is necessary to avoid cracking or damage to the arrises of the flags Not just the visible finishes of a floor but also its structural elements may be of special interest. The painting of floors to imitate tiling is an unusual feature of some eighteenthcentury houses; here the painted diamonds are shaped with pleasing eccentricity to fit into the available space
- CHAPTER 11 INTERIORS Architectural Heritage Protection Guidelines for Planning Authorities 174 floor is made of doweled floorboards, which would be irreparably damaged by lifting. Flooring such as terrazzo, scagliola and other composition materials are also extremely easy to damage and difficult to repair. 11.2.9 The cutting of old timber joists for new services should be avoided or kept to a minimum. It should be a requirement that any historical features, such as acoustic insulation or fire-proofing incorporated within the floor structure, should be preserved wherever possible. Where the need for improved fire protection demands the removal of such pugging, a full recording of the floor details should be undertaken before works commence. 11.2.10 Original floors and floor levels should be retained where they survive. In structures where the floor to ceiling heights are considered too low for modern habitation, consideration could be given to excavating the ground floor level or to raising the collars or ties of the roof in order to avoid raising wall heads. However, for an interior of significant quality or rarity, such proposals may not be acceptable. Floor strengthening 11.2.11 Any works to strengthen the floors of an existing building can be very invasive. Major disturbance can be caused to floor surfaces, skirting, panelling, architraves, hearthstones, ceilings and cornices. All options should be considered to avoid irreversible damage or needless disturbance of important features. 11.2.12 There are no standard methods of strengthening the floors of old buildings. Where floor strengthening is proposed, the applicant should be able to show that there will be a minimum disturbance of good quality finishes and a minimum loss of historic fabric such as floor timbers. Other options should also be explored, such as restricting the location of heavy loads to basement areas or to areas of little architectural interest where the floors can be strengthened without damage to important features. Low-key methods of stiffening floors are often possible and practicable using traditional methods and materials such as scarfing on new timber, the use of flitch beams and other solutions. 11.2.13 Any substantial strengthening work should be carried out under the guidance of an appropriately qualified structural engineer with knowledge and experience of historic buildings. Methods and specification for the works should be approved by the planning authority before any works commence. These sixteenth-century corbels continued to be used after an early alteration that raised the ceiling height. This change is of interest, adding to our knowledge of the evolution of the structure, but a similar proposal made today would require very careful scrutiny Proposals to strengthen historic floor structures should take account of the potential impacts on the fabric of the building and any existing finishes that would be disturbed to accommodate it. In this case, the main beam supporting the floor above is a scarfed beam. The scarfing may be original to enable the beam span a wide space, but could also signify an old repair, in which case the reasons behind the earlier repair work should be investigated to rule out the possible overloading of the floor structure Walls and partitions may be of interest due to archaic methods of construction, unusual materials or high quality of finish. Whether original or a well-crafted later intervention, as is this panelled bedroom corridor, internal walls and partitions can contribute to the special interest of the structure
- Architectural Heritage Protection Guidelines for Planning Authorities 175 CHAPTER 11 INTERIORS Internal walls and partitions IDENTIFYING SPECIAL FEATURES FOR PROTECTION 11.2.14 The walls and partitions in historic buildings may often be of interest in themselves and include examples of rare or interesting construction methods. 11.2.15 Earlier fireplaces, openings or decoration may be hidden behind later work. In protected structures where there are likely to be concealed features, the internal walls should be carefully investigated in advance of any alterations being carried out. However, where an earlier feature is known to be concealed by a later decorative scheme of interest, the later decoration should generally not be disturbed in order to reveal or investigate the earlier feature. CONSIDERATION OF PROPOSALS 11.2.16 In addition to the loss of historic fabric, the removal of internal structural walls or chimney breasts also has the potential to jeopardise the structural stability of a building and any proposals should be given careful consideration. 11.2.17 Where new partitions are proposed, they should be installed in such a way that they can be removed at a later stage with little or no damage to the historic fabric. New partitions should not cut through decorative plasterwork, finishes or joinery but be scribed around them with extreme care and accuracy. The installation of new partition walls should generally be avoided in high-quality interiors. 11.2.18 The formation of new openings in existing walls or partitions should be minimised, or avoided altogether, in an interior of quality, as this inevitably leads to the destruction of existing fabric. Such damage can rarely be satisfactorily reversed. Some injudicious alterations may include the removal of plaster from brick-nog partitions, while the cutting of new openings in braced partitions may result in structural failure. 11.2.19 The addition of internal insulation or dry-lining to a protected structure should only be permitted where this would not adversely affect important internal features of interest such as cornices, wall panelling, skirtings, windowcases and doorcases or decorative finishes. Ceilings IDENTIFYING SPECIAL FEATURES FOR PROTECTION 11.2.20 Ceilings that have plaster decoration are important features in an interior. Even plain plaster that is old is also of interest, particularly if it was applied onto Later finishes or features may cover earlier elements of interest such as this sixteenth-century doorway, partly covered by reused original panelling and an eighteenth-century doorcase; it may be necessary simply to record the earlier feature while retaining the high-quality later work in place undisturbed New partitions, where considered acceptable, should avoid disturbing historic fabric. They should be scribed around cornices, dado rails and skirtings to allow removal without damage. However, it is not generally recommended that important spaces within a protected structure be subdivided even if the subdivisions are reversible Evidence may survive on a plastered vaulted ceiling or arch of the wicker centring used in forming the vault, seen in the hollows left by the wickerwork which was embedded in the plaster and left there when the centring was removed. In some rare examples, pieces of wickerwork also survive
- CHAPTER 11 INTERIORS Architectural Heritage Protection Guidelines for Planning Authorities 176 Lath and plaster ceilings or walls without embellishments may appear unimportant, but the craftsmanship in their fabrication and the resulting gently undulating surface can be part of the character of a historic interior. Functional fixtures such as meat hooks, ventilation grilles or exposed beams contribute to the character (although plastered beams should generally not be exposed) Repairs to plastered ceilings should be appropriately specified to rectify any structural faults while avoiding unnecessary removal or reproduction of parts of the ceiling. Existing cracks and stains, while indicative of damage, should be monitored for ongoing problems before any invasive action is undertaken. Decorative ceiling plaster should be carefully repaired by an experienced conservation stuccadore, who may advise reinforcing the ceiling from above This illustration, taken in the space above a previously-lowered ceiling, shows the drawback of carrying out such works; apart from the damage to the architectural character of the interior, the lowered ceiling has concealed problems caused by lack of maintenance to the fabric above it timber laths. Decorative plasterwork may include highly decorated enrichments or relatively simple cornices. Ceilings may also be painted or incorporate painted panels. 11.2.21 Exposed roof or ceiling structures are of architectural interest and important to the character of an interior. These might include timber joists or trusses or iron beams. There may be associated details of interest to a ceiling such as iron or timber ventilation and heating grilles, lighting fixtures or chandelier winches. CONSIDERATION OF PROPOSALS AFFECTING CEILINGS 11.2.22 It should be noted that where there is a proposal to alter or dismantle a historic decorative or plain plaster ceiling, the alternatives should first be considered. Irregularities in a ceiling surface do not necessarily indicate problems which require the ceiling to be demolished. An undulating ceiling surface may need to be appreciated as part of an old building. Proposals to replace or alter the supports of a historic ceiling should be carefully scrutinised. 11.2.23 Proposals to install new suspended ceilings should be carefully considered and care should be taken that they do not conceal original plasterwork or other features of quality and that their installation does not affect the proportions or character of an important room or the appearance of a building from the street. Whilst they may be considered acceptable in minor rooms, or in spaces without special interest, they should generally not be permitted where they conflict with the window head level and where this would affect the external appearance of a building. Where new suspended ceilings are permitted to be installed, the installation should be readily reversible without damage to the historic fabric of the building. 11.3 Finishes Plasterwork IDENTIFYING SPECIAL FEATURES FOR PROTECTION 11.3.1 Historic plasterwork should be identified and protected wherever possible. Not only decorative wall and ceiling plaster, but also plain, flat plasterwork are important parts of the internal fabric of a protected structure.
- Architectural Heritage Protection Guidelines for Planning Authorities 177 CHAPTER 11 INTERIORS CONSIDERATION OF PROPOSALS AFFECTING PLASTERWORK 11.3.2 Care should be taken when permitting works such as chasing-in of electrical wiring that the minimum possible disturbance is caused to important wall or ceiling plaster. Where the plasterwork is of particular importance or rarity, chasing-in should be avoided. Disturbance should not be permitted to decorative plasterwork such as cutting through or across mouldings or installing downlighters. 11.3.3 Where older, soft lime-based plasters are to be repaired, repairs should be carried out using a plaster that matches the existing material on a likefor-like basis while allowing it to be clear on close inspection which is the original material. Joinery IDENTIFYING SPECIAL FEATURES FOR PROTECTION 11.3.4 Elements of internal joinery often survive in large quantities in historic buildings. They can include doors, doorcases, windows, windowcases, skirtings, dado rails, panelling, staircases and fireplaces. The doorcases and windowcases can consist of architraves, plinth blocks, door leaves, panelled reveals and window shutters. Surviving door and window furniture such as hinges, locks, lockcases, door handles, shutter bars and the like should be preserved even when redundant. CONSIDERATION OF PROPOSALS AFFECTING JOINERY 11.3.5 The planning authority should encourage the careful repair of the historic fabric with an emphasis on the conservation of as much as possible of the old material. Large-scale renewal of sections of joinery for the sake of convenience should be avoided. In repairing joinery, only the minimum amount of timber should be replaced using timber of a matching species and grain type. New pieces, where required, should be carefully jointed in. The profiles of decayed sections of moulded work should be copied exactly and spliced precisely into the existing work. The use of substitute materials such as glass-reinforced plastic to simulate carved joinery should not be permitted in interiors of architectural merit. Decorative plasterwork is of prime importance in historic interiors. Not only is it aesthetically pleasing, it can also be used to indicate dates of construction or alteration. The best eighteenth-century Irish plasterwork has an international reputation, but the more modest examples found countrywide are of importance to the houses, churches, town halls, railway stations and other building types which they embellish Plaster is generally a robust material, but continuous saturation can cause severe damage, both to the plasterwork and its timber supports, and provoke fungal attack in the latter. The fabric of the building will require drying out before an assessment can be made as to the extent to which replacement of plaster is necessary The internal joinery of a protected structure, whether original or good-quality later additions, is often aesthetically pleasing in addition to being well-crafted from high quality timber with good metal fittings. Joinery elements, whether of painted softwood or elaborate polished mahogany, are key indicators of the date and social status of a historic structure and provide a physical record of the alterations made to it throughout its history
- CHAPTER 11 INTERIORS Architectural Heritage Protection Guidelines for Planning Authorities 178 Timber is eminently capable of repair. Splicing, scarfing and other traditional methods of work that retain the maximum amount of sound material are still carried out effectively and unobtrusively by skilled conservation joiners The installation of new locks, catches, hinges, door-closers and other items to high-quality joinery, such as this mahogany door, can be carried out with care but should not necessitate the removal of surviving historic fittings even where these have become redundant. The removal of inappropriate later fittings can cause as much damage as their installation: the consequent repair is a specialist task The intact survival of delicate internal finishes such as historic wallpaper or stencilling is unusual; however, in this illustration, an entire early twentieth-century heraldic scheme has survived in a vaulted entrance lobby and been retained despite a recent change of use The repainting or redecoration of walls, or parts of walls, which never had important decorative schemes will not affect the character of an interior but the opposite will be the case where there are details of interest, such as these historicallyimportant mural panels
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