Existing fabric of the listed building
It is vital that the unique characters of historic homes are not put at risk by
unsympathetic alterations, unnecessary intervention, or changing environmental conditions: each owner is, after
all, only a temporary guardian of this heritage. When considering refurbishment, it is the owner’s responsibility
to ensure that any work does not cause unlawful or unnecessary damage to the building (fabric and indoor building
Older properties, and especially historic buildings, need to ‘breathe’ through the entire envelope (i.e. the
external walls, floor and roof), allowing moisture to escape and so preventing damp. A thorough understanding of
each building’s unique environmental characteristics will avoid detrimental effects to the building’s breathability
caused by misguided material changes.
As a first step, specialist guidance should be sought from the local building conservation officer and, ideally,
at least one of the organisations listed on page 2 of this guide. While detailed general rules are not appropriate
for individual historic properties, preparation work should include the following:
1 A good understanding of the building’s historic significance (refer to the Listed Building Description or
Conservation Area Designation if applicable): this will help to create a sympathetic approach to the existing
building materials and structure.
2 An assessment of the building’s heating and ventilation needs.
3 A presumption of minimal intervention.
4 If possible, any new work should be designed to be reversible by future generations.
Modern homes use physical barriers to stop moisture from penetrating the building envelope, whereas older homes
tend to be made of porous materials and are permeable. Be aware that there is an important difference between
porosity and permeability:
Porosity is the ratio of the volume of pore space to the total volume of a solid material. Pores may or may not
Permeability is the rate at which a liquid or vapour passes through a solid material. Pores must be
Modern materials such as concrete or plastic are often inappropriate for use in older homes, harming aesthetics