When repairs to historic buildings become necessary, they should be approached using the basic principle of conservation, that as much as possible of the original fabric of the building is retained.When repairs to historic buildings become necessary, they should be approached using the basic principle of conservation, that as much as possible of the original fabric of the building is retained.
Too often a decision is taken to strip away large parts of the original material, and to replace with replicas. An historic building, however, loses its historic integrity when a substantial proportion of its original fabric is replaced, as well as the patina which materials gain with age. The replacements used are often not exact replicas, and thereby also result in the loss of a building's educational value
Unlike endangered plants and animals that can be encouraged to increase their number through relatively short reproduction cycles, each historic building is different and once lost can never be replaced. Repairing original building elements is often cheaper than manufacturing modern replacements. For these reasons we recommend that you employ an architect who is experienced in repairing historic buildings. The fees applicable to the historic building element of any works are eligible for grant assistance under the approved repair scheme. Professional guidance can often mean the difference between a smoothly run, successful scheme and one that results in the loss of much valuable material.
Windows and doorsIt has been said that the windows are the eyes of a building. Certainly they are the element, that if replaced unsympathetically, will do the most to alter the character of a building. Most of the listed buildings in Northern Ireland have wooden sash windows. These will usually be between one hundred and two hundred years old but with professional repair and conservation they may last for another hundred years, making repair a sound economic and environmentally friendly propositions as well as being historically vital.
Common reasons given for replacing windows are that they are draughty or rotten, or that they stick or cannot be opened. All of these problems can be rectified by an experienced joiner, and serious consideration should always be given to conservation rather than replacement.
There may be occasions where a window is beyond repair and where this occurs it should be replaced with a replica using the same material. The joiner should take particular care to match the details of the sash boxes, glazing bars and patterns, and any horns or shutters of the original. Crown glass, an important feature, should be retained when windows are being refurbished. This was only superseded in the middle of the nineteenth century, when float glass was invented allowing the manufacture of larger pieces of glass. Crown glass has a distinctive sparkle and slightly distorts images when looked through. Existing stone windowsills in good condition should not be replaced with slim line concrete sills. Click here for more information about wooden windows.
The same criteria used in dealing with windows also apply to the internal and external doors of your building. Where internal doors are required to be fire resistant they can now be modified, rather than discarded. Traditionally, external joinery was painted, windows white and doors a different colour. If you decide to recreate the original colour scheme paint scrapings can be taken and matched with colours available from specialist manufacturers.
Gutters and DownpipesFaults in rainwater goods will quickly lead to saturation of adjacent areas of wall. In most listed buildings gutters and downpipes will be made from cast iron. This is a very resilient material and often will clean up very well and be reusable. It is essential that, if part or all of the system needs to be replaced, cast metal, preferably cast iron, is used. Most modern lightweight alternatives, as well as being out of place historically, are prone to damage from ladders. It is also important that when replacing gutters care should be taken not to alter the eaves detail, for instance by introducing timber or PVCu fascia where there wasn't one before.
Pointing and RendersApart from incorrect windows, these are the elements of a building that if not repaired correctly can do most to destroy the character of your building. Again the criteria should be only to repoint and replace render where absolutely necessary. Severe damage can be caused to brickwork and stonework by using angle grinders to remove mortar. If this method seems necessary to extract existing mortar it means that in fact it does not need to be replaced.
Most remaining historic buildings constructed before the discovery of Portland cement in the middle of the nineteenth century used mortars bound together with lime and, if rendered, lime render. Those built after this time were still constructed with mortar where the binder was mainly comprised of lime. These mortars are flexible and allow buildings to breathe and move slightly without cracking. When cement based mortars are used in repairs they are less flexible and prevent the natural evaporation of moisture through the mortar joints. This can cause dampness and also force the moisture to pass through the bricks or stonework resulting in unsightly salts being deposited on the face of your building, and fracturing of the wall face.
As you can see, it is crucial that if mortar has to be replaced every effort must be made to match the original mortar in content and appearance. If necessary this can be achieved by chemical analysis. Suitably graded sand and aggregate of a matching colour will be obtainable locally, and lime putty is available from at least two suppliers in Northern Ireland. 'Harling', the local name for traditional roughcast, has a soft rounded appearance not only because of the coats of lime wash applied over the years, but because river gravel was often used as the aggregate.
The method of pointing is also visually very important and when re-pointing, particularly in terraces and groups, every effort should be made to match the appearance of the original. 'Strap' pointing and 'recessed' pointing are to be avoided. Joints should be raked out to three times the depth of the joint, the bed wetted, and mortar rammed home in three layers; otherwise the new mortar will not adhere properly and may fall out after a short time. Re-rendering with a cement based render or redecorating with a waterproof coating in an attempt to stop water penetration can have a harmful effect, as the wall will not be able to breathe.
Roof coveringsThere are three main types of roof covering materials used on listed buildings in Northern Ireland - natural slate, thatch and lead sheet. Original materials and methods of fixing should be respected and fibre cement slates and concrete tiles should not be used in repairs. The public's perception of thatch has largely changed, and now in parts of the UK and Ireland the craft of thatching is enjoying a revival, with both old and new thatched properties selling at a premium. There are, however, only about one hundred thatched buildings left in Northern Ireland, and in an effort to encourage owners to maintain thatch roofing we offer generous grants for repair and maintenance above the level for other works.
Other elementsInternal details and materials of a building are as important as the external. Original plasterwork, joinery, including stairs and window encasements, floors, skirtings and fireplaces all contribute to the value of a building. Often existing materials can be carefully removed, stored and reused. Similar materials are frequently available second-hand, such as bricks and natural slates. It is well worth identifying a source of similar materials before starting works as otherwise delays may be experienced, and your builder may press for the use of inferior or inappropriate modern materials in order to save time.
The SettingThe setting of a listed building is often extremely important and is protected by legislation from detrimental development. Too often gardens, gates and gate posts are sacrificed to provide wider access or additional car parking resulting in the degrading of the building's setting. In many cases the setting of a building was specifically designed to enhance the property. Examples range from the English landscape style of the eighteenth century encompassing entire demesnes, to the more modest avenue of trees leading to a country house or church. The most important examples of historic gardens and designed landscapes have been surveyed and recorded in the Heritage Gardens Inventory 1992.
Historic buildings as well as being important individually were sometimes designed to be appreciated as part of a group, for instance in a square or terrace. This group value can apply even to modest buildings. It can often be enhanced by the owners agreeing to joint painting schemes and other group actions that could mitigate the possibility that the decision of an individual owner will damage this group context. For instance, if one building in a stone faced terrace is cleaned whilst the others are not, it will stand out obtrusively, instead of taking its place in the total composition of the group.
Gates and gateposts are often an integral part of the setting of a building. In rural areas the traditional iron gates and stone pillars are important not only to the individual building, but to the rural environment generally and so are worth maintaining just as much as the buildings themselves.
For more information please see Environment and Heritage Service's series of Technical Notes.