Key Differences Between Older and Newer Buildings
Older and newer buildings have been built very differently.
Older buildings have been designed and built to be water permeable. Being built from breathable materials, they allow for a large percentage of the moisture to freely evaporate.
Newer buildings on the other hand are being built watertight using modern materials (including many plastics) designed to keep moisture entirely out.
As a result, old buildings should be treated and repaired differently from newer buildings. They should be renovated with similar, traditional materials with as little destruction to the building fabric as possible. Modern materials designed for older buildings, without without an extensive knowledge of materials and/or building physics, should be avoided as much as possible. These materials, in older buildings hinder evaporation and the accumulating moisture and salts can severely damage the wall fabric long-term.
Mixing old and new technologies can have detrimental effect on old buildings, often leading to the decay of the old building fabric.
Removing or reverting the new, non-breathable materials does not necessarily solve all dampness problems, but restoring breathability often results in a significant improvement.
Who Do You Take Advice From?
If you own or are about to renovate an old building, please do your homework and take advice from professionals who are knowledgeable about old buildings and building materials - not just your average builder.
When dealing with longstanding dampness problems, it's best to ask the opinion of a specialist who understands old buildings, materials and has the "holistic" view on dampness (how moisture move inside the build, what is affecting and influencing what etc.). A competent dampness investigation will save you money in the long run most of the time, by helping you understand in-depth problems you are about to tackle so you can make an informed decision. This is faster and less costly than the "trial and error" approach.