PPS 6: Planning, Archaeology and The Built Heritage
Annex E: Building Elements
E4 The following paragraphs will look at each building element in turn and examine the general criteria that will be applied in assessing proposals for works to listed buildings. It is impossible to describe every situation and problem that can arise and the guidance does not purport to be a manual of good conservation practice and should not be used as such. Those seeking more detailed information about any aspect of conservation work referred to briefly in this annex should contact the Department’s Environment and Heritage Service at 5 - 33 Hill Street, Belfast where further advice will be available.
E5 The roof is nearly always a dominant feature of a building and the retention of its original structure, shape, pitch, cladding and ornament is important. Natural slate and lead are the most common materials to be found on the roofs of listed buildings in Northern Ireland. Other roofing materials include thatch, tiles and copper. These traditional roof coverings should be retained wherever possible and their replacement with modern substitute materials will not normally be acceptable. The relationship of the roof to the supporting walls at verges, eaves and parapets are also important features and part of the historic character of most listed buildings. Such details should not be altered during renovations. Where original timber or metal framing remains in a roof this too can contribute greatly to the historic interest of the building as a whole.
E6 The provision of roof ventilation will normally require listed building consent as it is likely to alter the appearance of the building. Where such work is proposed it should be undertaken without disfigurement to the roof, so thought will be required before deciding on a suitable method. There is a wide range of manufactured items to choose from. If it is the intention to use a standard item then it will be helpful if a section of trade literature is submitted with the listed building consent application in order that the precise item type, material, colour etc. can be established. An alternative is to copy the design of traditional ventilators.
Dormers and Rooflights
E7 Original dormer windows should be retained and carefully repaired. If beyond repair they should be reconstructed with all details reproduced. Enlargement of existing dormers on principal elevations should normally be avoided. Any decision as to whether new dormers or roof lights can be added to a roof must be approached carefully. Historic roof structures must not be damaged by their insertion. This can be difficult to achieve as original ties and braces can get in the way and where alterations would result in large scale loss of original fabric they will not be acceptable. New dormers should not upset a symmetrical design of an historic building, while in terraces their introduction may be inappropriate in townscape terms. New rooflights may provide an alternative in such cases, although they should be in flush fittings and not located on prominent roof slopes.
E8 These are essential elements for most listed buildings and are important to their silhouette and three dimensional character. In some instances they will be part of the formal architectural composition. In terraces and groups the exact form and detailing can be critical to the overall architectural concept. In many cases chimneys also perform a vital structural function and they should generally be kept whether or not they continue to have a functional use. When it is necessary to build a new chimney it must be considered as a positive part of the listed building. A stainless steel tube bracketed to the wall can only detract from the character and quality of the parent building. Chimney pots, especially in groups and terraces, are often an important architectural element in their own right and a traditional roofscape may be damaged if they are removed.
E9 Rainwater goods should not interfere with any mouldings or decorative features. The profile of guttering and the positioning of downpipes are often part of the formal architecture of a listed building and are to be respected in any scheme of work. Where the contribution of the guttering is less formal it will still be important to keep to original profiles and to use traditional materials.
External Wall Finishes
E10 Most listed buildings are stone, brick or rendered, a few are faced in faience or terracotta or are half timbered. Of these finishes, render is the one most prone to inappropriate changes. The character of an historic building can be considerably altered by choosing a render that has not been based on a proper study of historic mixes. To render over stone and brick finishes will not normally be acceptable because of the resulting change to the building’s character. Equally it will be wrong to strip render to expose stonework if it is clear that the building was historically rendered. When considering a new render particular attention should be given to the choice of sand and aggregate in the mix, as this choice will affect both colouring and texture. Modern rendering techniques such as dry dashing are rarely appropriate.
Inscriptions and Other Features
E11 Inscriptions, date stones, coats of arms etc. are all an important part of the history of a building and such features should be retained in situ wherever possible. Signs and advertisements will require listed building consent. Where considered acceptable in principle they should be carefully designed and positioned with appropriate fixings that will not damage the building.
E12 As a rule, windows in historic buildings should be repaired, or if beyond repair should be replaced “like for like”. In considering listed building consent applications for additional windows it is important that their design, scale and proportion should be sympathetic to the character of the building. The fact that owners so often wish to alter windows demonstrates that windows attract the attention of practically anyone who objectively looks at a building. They are the eyes of the building and they catch the eye. The finish, the material from which they are made, the method of opening, the subdivisions of the glass, the characteristics of the glass, the interplay of panes, the profiles of each component, the relation of sills, architraves, encasements, shutters etc. all play their part in the overall character of the window. The window plays a vital role in the overall appearance and character of the building internally as well as externally.
E13 Old windows were generally made of sturdy materials, they may look shabby and rundown and they may fit badly and admit drafts but nevertheless it is possible, more often than not, to repair and restore the original units. Repair rather than replacement should be the first aim in any scheme for a listed building. Original timber sliding box sash windows and casement windows can be fitted with seals, gaskets and improved ironmongery to provide a performance that will match any modern window type.
E14 Within the broad window types such as sash or casement there is a wide variation of detail according to date, function and region. Standardisation to one pattern should be avoided. The thickness and moulding of glazing bars, the size and arrangement of panes and other details should be appropriate to the date of the building or to the date when the aperture was made.
E15 The insertion of factory made standard windows of all kinds, whether in timber, aluminium, galvanised steel or plastic is almost always damaging to the character and appearance of historic buildings. In particular, for reasons of strength the thickness of frame members tends to be greater in plastic or aluminium windows than in traditional timber ones. Modern casements with top-opening or louvred lights or asymmetrically spaced lights are generally unsuitable as replacements for windows in historic buildings. Such alterations will not therefore be permitted be allowed. Architects’ drawings and specifications should make clear the manner in which new windows are intended to open.
E16 It is usually impossible to install double-glazed units in existing frames without altering the character or appearance of a listed building. Listed building consent is quite likely to be refused for such an alteration because the form and detailing of windows is so often a key architectural element of historic buildings. The more complicated the glazing pattern the more difficult it will be to double glaze and for the installation to meet acceptable conservation standards. Conversely, where there is a simple undivided single sheet of glass in each frame double glazing can usually be fitted without any appreciable change to the appearance and character of the window.
E17 Where there are difficulties, the first step is to discover, by calculation, whether or not double glazing would provide a material benefit in controlling heat loss. Traditional internal timber shutters and good quality curtains will give an equal performance during the hours of darkness. However, heat may be lost through other routes. Commonly this is via the air gaps around badly fitting frames. The installation of draft strips and weather seals is a simple and very effective procedure. Reglazing with thicker single sheet glass or the installation of secondary glazing are other options that will not normally require listed building consent. Plastic strips simulating glazing bars and sandwiched into the cavity of the double glazed unit are not an acceptable conservation option.
E18 In certain circumstances trickle ventilation will be a statutory requirement. There are a variety of ways to modify the designs of traditional windows to make this provision and there are ventilators available that have been specially designed to meet conservation criteria. Where difficulties arise it is as well to remember that the purpose of the ventilator is simply to ventilate the room; it is not a requirement that it be provided through the window. Other locations should therefore be assessed in difficult circumstances.
E19 Original doors, both external and internal, and their encasements are important elements in listed buildings and wherever possible they should be retained. Their replacement or defacement is often entirely unnecessary. The main features that characterise doors are their size, shape, proportions, the method of construction and individual details such as fanlights or knockers. Timber doors may be sheeted or panelled. The panels may be flush, recessed, fielded and may be decorated with mouldings. Finishes are important as are ironmongery and fittings. Replacement doors should copy the original in the materials, the detail of design and the paint finish. Modern off-the-peg doors are not generally acceptable for use in listed buildings, nor are doors with incongruous design features such as integral fanlights. or furniture such as knockers, letter boxes or moulded details should not be removed or mutilated but retained even if the doorway is redundant.
E20 A modern threat to original doors is protection against fire. Consideration should always be given to ways of retaining original doors. These may include fitting a second door to create a lobby, providing additional escape routes, or investigating a fire engineering approach. Sometimes work to original doors cannot be avoided, but there are techniques that provide the required fire ratings with only minor loss of character. It should also be noted that it is now possible to obtain a waiver for listed buildings from the requirement under fire safety legislation to raise door heights to modern standard heights.
E21 Door and window openings establish the character of an elevation and should not generally be altered in their proportion or details. Alterations will only be considered where all reasonable alternatives for continued use have been carefully examined. Sometimes such alteration is unavoidable, but it should be noted in load bearing masonry walls this will almost always create a structural weakness for all time. Where it is proposed to close existing openings it will be important that evidence of that opening is featured in the new work. Sometimes this will entail the retention of the window or door and blocking in behind. This is particularly important in terraces for the sake of the overall design of the terrace. On other occasions it may be acceptable to simply recess the blocking to maintain the outline of the old opening or to conserve a sill or an architrave as evidence of the change. In this way the pattern of change can add to the historic interest of the building.
E22 Old shop fronts are already very rare. Wherever shop fronts of merit survive they should be retained and any alterations will require the greatest care and attention. Features of value such as blinds in blind boxes, shutters in shutter boxes against an upright and stall-risers should be retained. Often such features are concealed behind later alterations and premises where works to shop fronts are proposed should be checked for the possible survival of such features. The major threats to old shop fronts are security, fashion, advertising and the corporate image. However, there are almost always ways to meet reasonable working needs without resorting to wholesale change and increasingly, in the commercial world, it is now being recognised that individualism, when it is of good quality, is often better for business than thoughtless standardisation.
Shop Blinds and Security Grilles
E23 Retractable apron blinds covered in canvas are often characteristic features of historic shopfronts and should be retained. Modern plastic canopies are not acceptable. External steel roller shutters are not suitable for historic shopfronts. Acceptable alternatives include laminated glass and internal shutters.
New Shop Fronts
E24 New shop fronts should be designed in sympathy with the rest of the elevation and incorporate any ground floor details of interest. Large inserted plate-glass shop fronts without any visual support for the upper part of the premises can have an unfortunate effect, and shop fronts should not extend into the storey above or alter the proportion of first floor windows. Modern materials such as plastics are to be avoided as facings. The fascia board should not be out of scale with the building as a whole and should usually be finished at the top with console brackets and a cornice or other capping. Not only is this the traditional treatment for shop fronts but the cornice provides an architectural division between the modern shop front and the old upper floors.
E25 Depending on the nature of a proposed commercial or office use, it is very often unnecessary to provide display windows and thus alter an intact ground floor. Existing openings should be retained wherever possible, and if alteration is necessary it should only be to the minimum extent required. Standard corporate shop fronts are seldom appropriate for historic buildings, nor are internally illuminated fascia boxes or signs. The prestige value of listed building premises and their distinctive detailing can be emphasised instead.
E26 Where original ironwork exists it is often an important feature sometimes giving unity to a group or terrace of historic buildings. Local foundries and blacksmiths developed individualism in their work and this local flavour can give a particular character to an area or locality. Broken cast iron can be repaired and damage should not be regarded as an excuse for removal. In some areas there is pressure to convert gardens and yards to parking but if this means loss of ironwork or other important features or if the proposal intrudes into a unified landscape, proposals are likely to be refused.
E27 A new conservatory is a new extension and the same criteria for a successful listed building consent application pertain as for any other extension. The first consideration is the relationship of the proposed new structure to existing architectural features. The second is the intrinsic quality of the new design and the third is the sympathetic choice of materials and finishes. The design can be thoroughly traditional or thoroughly up to date. Whichever is chosen it must have a quality that will equal the qualities of the parent building.
Parapets and Other Features
E28 Parapets (solid or balustraded), pediments, parapeted or coped gables and saddlestones, eaves, cornices and moulded cappings are essential terminal features in the articulation of an elevation of an historic building. If they have to be replaced, it should be in facsimile and in the same materials.
E29 Porches are sometimes the dominant feature of an elevation; their detailing should always be respected. Open columned porches of the classical type should not normally be enclosed (e.g. with glazed sides and doors to the front), but should be left open. In those instances where new porches are considered acceptable, their design should be undemonstrative and should not challenge the integrity of the facade.
Balconies and Verandas
E30 Balconies and verandas are very often formal components in the design of an elevation. They should be maintained and repaired wherever possible; and if they have to be replaced, facsimiles should be erected using matching materials. As with porches they should not normally be enclosed with glazing.
E31 Doors have been discussed separately at E19 above. Equally important to the special interest of many historic buildings are other internal features such as original floorboards, stairways, dadoes, balustrades, panelling, skirting, chimneypieces, chimneybreasts, decorative plasterwork and in some of the more important interiors the paintwork, gilding, gesso etc. Very often important early features may be brought to light during refurbishment works. Fittings too are often of considerable historic and/or architectural importance; for example curtain fittings, early light fittings, sanitary and kitchen fittings, mirrors and built in paintings. While it is more difficult to generalise about interiors than the external elements of an historic building, all internal features and fittings of interest should be respected and left unaltered as far as possible.