Understanding heritage buildings has a lot to do with understanding the materials they are made from and how they work as a whole. Grasping this can help you to protect and repair your church, chapel or meeting house, without adversely affecting the heritage, either now or in the future.
There are fairly standard timber framed or stone built structures, found across the country, and there are those made from a more local and therefore specialist materials, such as the flint churches of the south coast. Either way, it is vital that you only maintain or repair with like for like materials, in order to protect and enhance your church heritage.
Stone, brick, timber and earth
Traditional main building materials like stone, old brick, timber and earth are all absorbent, and relatively ‘soft’. They allow the building to both breathe and building to move slightly. They should always be replaced like with like, even if this means sourcing specially made materials.
Traditional buildings are peppered with features which both protect and enhance the whole. These include stone gargoyles to throw water away from the walls, and lead flashing to protect gutters and valleys and stone.
Lime, lime and more lime
In order to breathe and move, traditional main building materials must be paired with the right mortar, plaster and other sympathetic joints and coverings. This usually means using traditional lime mortars and plasters, which also breathe and allow movement.
Society for the Protection of Ancient Buildings: Lime
The scourge of the modern
Why would it be such a problem to use modern materials on a heritage building?
Modern materials, such as hard bricks, cement-based mortars and renders, modern paints and external sealants are specifically designed to keep moisture out of the building by creating an impervious physical barrier. They are also designed to be solid, rigid, inflexible.
Whilst it may be tempting to use easily available and cheaper modern materials, you should not. They can seriously affect the breathability of a building, meaning that moisture cannot escape and causes huge damage inside.
If you look at an old building which has been re-pointed with a hard, waterproof cement mortar you will see that the stonework has decayed much more than that around the re-pointed area. That is because moisture cannot escape through the hard cement and is now evaporating through the stone rather than through a lime mortar as it should, leading to leaching, excessive decay and spalling (when the front face of the stone flakes off).
Modern hard materials also affect the flexibility of the structure, potentially leading to cracks and breaks between sections.
Traditional materials research
Historic England, together with other organisations, undertakes research to understand risks to the built environment and the technical means to conserve it.
Historic England: Building Materials for Historic Buildings