Fundamental 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.
Mixing old and new technologies has a detrimental effect on old buildings, usually leading to the rapid decay of the old building fabric.
Most Important Factors Of Decay
The most important factors responsible to the decay of old buildings are the following.
Moisture is the #1 enemy of old buildings. The fabric of old walls often contains significant amounts of moisture. Most of this originates from the outer environment These can originate from multiple sources such as:
- The air: in form of (driving) rain, sea-spray, fog etc.
- The ground: as rising damp, penetrating damp (in cellars), water splashback.
Water dilutes existing salts in the environment and transports them into the building fabric. When moisture evaporates the salts crystallize, making them expand in volume 5-10 times, leading to the cracking and crumbling of the masonry.
Most common sources of salts are:
- Rising damp: salts absorbed from the ground
- Chimney soot: contains very high amounts of salts, responsible for the poor state of many chimney areas
- Leaks/water ingress: trickling water moves salts around, often depositing them to the surface
- The air: in form of sea spray, salty winds, or pollution from cars or nearby factories – these salts are washed by rain into the wall fabric.
3. Renovating with Non-Breathable Materials
The natural degradation of the old building fabric due to moisture and salts is further aggravated by the use of modern non-breathable materials (e.g. cement plasters, foams, plastic paints etc.) primarily designed for newer buildings. These materials, in older buildings hinder evaporation and the accumulating moisture and salts severely damage the wall fabric long-term.
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 (builders, architects, surveyors etc..) 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 most of the time will save you money in the long run, by helping you understand the nature of problems you are dealing with so you can make an informed decision - instead of the more costly and often frustrating "trial and error" approach.
On the following pages we are going to cover some of the practical fundamentals on various types of problems.
Hope you find this information useful.