Repairing and altering traditional buildings
Repairing and altering traditional buildings
The sensitivity of historic buildings
Historic buildings vary greatly in how much they can accommodate change without losing their special interest. Some are sensitive to the slightest alteration, especially externally, or where they have important interiors, fixtures, fittings or other detailing. Others may already have changed significantly during their lifetime and can accommodate change relatively comfortably. These considerations will influence the amount of further change that can be accommodated in response to climate change impacts or energy efficiency measures.
An early dialogue between the owners/occupiers, designers, building control surveyors, development control officers and conservation officers is usually to everyone’s advantage. Before considering any alteration, it is important to assess the elements that make up ‘significance’: the special character and interest of the building.
Significance depends on:
- External features including decorative façades, roof details, windows and doors.
- Plan and internal layout is one of its most important characteristics. Interior plans should be respected.
- Internal features of interest such as decorated plaster surfaces, panelling, floors, window shutters, doors and doorcases.
- Details such as mouldings, stucco-work, wall and ceiling decorations can be just as valuable in simple vernacular and functional buildings as in grander architecture, and can be a building’s most important feature.
Once the significance has been assessed, a ‘conservation statement’ or ‘conservation plan’ can be written. This sets out why the building is significant and how that significance will be retained in any future use, alteration, development or management. For many simple buildings this may be little more than a list of features. A conservation plan is therefore not a plan of works, but it is important for shaping current and future plans of work.
An understanding of what constitutes the special interest of a historic building requires experience. If there is any doubt, consultation with a local authority conservation officer is recommended.
Importance of maintenance and repair
Regular inspection and maintenance is vital and the first step in improving energy efficiency and maintaining the building’s ability to withstand extreme weather. A damp wall caused by a blocked gutter will be colder and loose more heat. Slipped tiles allow cold draughts. Ivy on walls reduces solar gain as well as exacerbating damp by preventing evaporation from the wall surface. The action of its roots can also lead to a loss of pointing. Flaking paintwork on windows allows water to get in, which in turn causes warping and draughtiness.
Before repair, it is important to identify and deal with the cause of the problem. Treating symptoms (a damp wall) without addressing the cause (a leaking downpipe) is pointless. If new materials or detailing are introduced, these should match the original as closely as possible, unless it is flaws in the original construction that have caused problems.
Checklist for adapting traditional buildings:
Understand the significance building
Some buildings, or parts of buildings, are of such quality, importance or completeness that they should only be altered at all in the most exceptional circumstances.
Check whether statutory controls apply
Find out whether the building is listed or in a conservation area. Also check with the local planning authority to see if other planning conditions are in place (eg if the building is in an ‘area of outstanding natural beauty’ , or if it is covered by an Article 4 direction, which restricts certain permitted development rights). The local planning authority will be able to explain the implications of such conditions. Check what consents are required and obtain them before starting any work.
Understand how the building is working
It is important to understand the current energy performance of a building, before taking any measures to improve its efficiency. For example, if a building is cold because of air infiltration, adding extra insulation to the loft will be pointless. If a building is already airtight, adding extra draught-proofing can lead to problems of condensation and the need to open windows for ventilation. If a building is known to be draughty, the sources of the draughts should be identified – draught-proofing windows and doors may be wasteful if cold air is actually coming through the floor or walls.
Understand the building fabric
The mortars, plasters, renders and paints of many traditional buildings are soft, flexible or permeable. They allow the fabric to respond to air, moisture and structural movement in ways that is fundamentally different to the hard, rigid, impervious materials and membranes widely used in modern construction.
Alterations should be compatible with the fabric that is being altered. This will allow the existing fabric to perform as intended, and to prevent problems at the interface between types of fabric. Modern methods and materials that would be appropriate on a new building may be ineffective and cause sequential damage in a traditional building. For example, incompatibilities in flexural strength, permeability and porosity of cement or gypsum-based mixes for plasters, renders and pointing can lead to damaging salt migration .
Minimise disturbance to existing fabric
The stock of historic buildings is finite and every loss or major alteration to fabric is significant. For that reason you should always try to minimise intervention into the historic fabric of the building. Piecemeal replacement of components diminishes the value of the remainder.
Even replacement of original materials on a like-for-like basis will cause the loss of historic evidence in the original fabric. For example even the most careful replacement of partially decayed beams with new beams will affect a building’s appearance and result in the loss of much of its history.
Wherever possible choose alterations that are reversible
Alterations should whenever possible be designed so that they can be reversed without damaging the existing fabric. This is especially important where the changes are to building services that involve rapidly evolving technologies and have correspondingly short lifetimes.
Use good quality materials and workmanship
If you use good quality materials and workmanship you will minimise the need for future interventions. Only make changes that are known to be effective, and use materials that have proven performance.
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