An historic interior has two distinct components: the structural framework of the room – walls, ceiling, floor, windows for example – and the associated content and decoration. The latter may be made up from surface treatments such as paint, wallpaper, tiles, textiles carpets and linoleum, as well as original fixtures like fireplaces, stained and painted glass, lighting, services and sanitary ware. Each element reflects fashionable trends of the period as well as giving an indication of the function of rooms and the status and personal taste of the occupants. Every aspect was usually carefully chosen to provide a backdrop to family life and to display personal possessions to best effect.

Some decorative finishes can be admired as works of art, and others may be valued as products of great craftsmanship or invention. Bear in mind though, that it is the role of all these different elements within the history and context of your interior which makes them an important part of our cultural archive. This guidance note deals specifically with painted, stencilled and wallpapered surfaces, but broadly the same principles are relevant to a wide range of finishes, fixtures and fittings.

• A conservator specialising in treating historic interiors will give you advice and recommend treatment. Professionals in this discipline often have a background in paper or paintings conservation, and have developed additional skills relating to historic structures, site work and building project management.

First considerations

If your house contains original decorative finishes, it may well be listed, so be aware that certain works will require planning consent. Contact English Heritage (Historic Scotland, CADW) or your local Conservation Officer. These bodies require that work done to the interior of a listed house should follow “best practice” - minimum intervention and as little disruption to the original surfaces as possible. Prolonging the life of original materials, finishes and fittings in an informed and sympathetic way is the aim, rather than replacement or restoration.

Refurbishing and making alterations to interiors

You may have come across a decorative scheme while refurbishing your property.

Alterations and home improvements can be an opportunity to understand the history of your building and make exciting discoveries. Any surviving evidence of a former interior scheme could be significant and is worth investigating. Take time to do some research; you might want to re-think your decoration or alteration plans as a result.

In the past, paint and paper were not always stripped before redecoration, but even where they have been, there is often enough residual evidence to identify and re-create the original scheme. Larger sections may survive hidden behind stud walls, in attics or cupboards and may provide an unprecedented record of decoration and the basis for an authentic re-creation.

• A specialist conservator in this field can give you information and advice on re-creating the original scheme or on how best to preserve the remains of an old scheme beneath a new one.

Why schemes deteriorate

Wallpaper is hygroscopic, it “wicks” up moisture and can become fragile and liable to be damaged in moist conditions. While damp it will also have absorbed atmospheric pollutants over the years - smoke from fires, cigars, candles and gasoliers and, more recently, fumes from industry and the internal combustion engine. The paper itself may contribute to its own decay - glues, wood pulp-containing papers and certain pigments may also contain acidic contaminants. Alkaline conditions can cause problems too - usually from damp plaster walls.

Paint is similarly vulnerable, and is damaged by light, heat and humidity. Within an historic interior these factors are made worse by the human element: exposure to daily traffic of people and animals, furniture being moved, pictures hung or a bath left to overflow. Central heating, condensation, open fires and structural defects leading to dampness such as blocked gutters, loose roofing tiles and inadequate ventilation all pose threats to fragile interior surfaces. Paint and wallpaper are also vulnerable to unsympathetic repair, restoration or replacement.

What can you do to prevent and alleviate degradation?

• Maintain good environmental conditions. For example, you can control daylight and its UV component by using blinds and UV filters on the windows. Reduce the use of open fires and other causes of dramatic fluctuations in temperature and humidity wherever possible.
• Maintain a regular housekeeping regime involving monitoring and inspection.
  Inspect and maintain the building shell as well as the interior: clearing gutters, checking roof tiles and preventing leaks.
• Try to limit human and animal contact with the surfaces, but do not use Perspex or coatings as protection, as these will only exacerbate any problems by trapping moist or stagnant air. Other physical barriers, or changing traffic routes through the room or house, may be more effective.
• Keep furniture away from the decorated surface, and do not screw, fix or nail anything to walls. Avoid damage from the installation of electrical or security services.
• Supervise decorators and other contractors on site; fragile surfaces are most at risk during building and decorating works.

Consulting a conservator

Work to the complex and multi-layered nature of original decorative schemes will usually benefit from the advice of a conservator from the outset of the project. They will be able to offer the following survey and treatment services:

Condition Survey

• Recording: Papers and paint schemes will be carefully photographed, documented and any additional historical evidence noted and retained.
• Assessment of condition. This may involve the conservator monitoring the room's environment to help identify reasons for deterioration and to indicate any improvements that may be necessary.
• Recommendations for treatment: Several options will be listed, dictated by location and future use of the room as well as environmental conditions and the nature and condition of the materials used
• Future care. A conservator may also provide a manual for the continued care and protection of the wallpaper or paint and you might find it helpful to arrange an annual inspection visit.

Treatment

A conservator can help by carrying out the following:

• In situ treatment. If the wallpaper or painted scheme and the surface of the wall substrate itself are sound, simple remedial treatments can be carried out in situ: surface cleaning, consolidation of any flaking pigment and simple repairs to small areas of damage. All conservation treatments will be reversible, will work effectively and will leave no potentially harmful residues.
• Removal and conservation of wallpapers. You may need to remove the wallpaper if there are structural problems, if a textile support has degraded or is loose, or if electrical work is to be carried out. Removal may also be the preferred option if the paper itself is deteriorating due to high levels of acidity.
• Preserving the decoration as fragments. If the scheme only survives in fragmentary form, or is in very poor condition, you may not want to display any of it. If the original paper or finish is removed and stored, make sure that it does not become disassociated completely from its historical context. In this case, a conservator can help by investigating, recording and preserving the original in situ. They can arrange the commissioning of an accurate reproduction on the basis of the evidence, or protect the original before hanging new paper by preparing and carrying out a special acid-free lining.
• Revealing and sympathetically incorporating fragments into the new scheme. This approach also works after conservation, where fire or flood has caused significant loss.
• Reconstruction. Your conservator can help you commission a reproduction once the design, the materials and the methods of manufacture or decoration have been identified. The most effective reconstruction is one which has the same quality and surface texture of the original.

Use the Conservation Register to Find a conservator.

© Icon, the Institute of Conservation 2011.

This article offers general guidance and is not intended to be a substitute for the professional advice of an accredited conservator. The views expressed are those of the author or authors, and do not necessarily represent the views of the Institute of Conservation.

The Institute of Conservation would like to acknowledge use of the MGC publication 'Ours for Keeps' in the preparation of this text. The Institute of Conservation and its partners accept no liability for any loss or damage which may arise if this guidance is followed.

The Institute of Conservation would like to acknowledge the support of The Royal Commission for the Exhibition of 1851 in the production of this guidance information. Further information on The Royal Commission for the Exhibition of 1851 and its work is available at www.royalcommission1851.org.uk.