Do we have more damp problems today than before?
| Such a question is naturally very difficult to answer. We can be fairly certain that people in the past were aware of the importance of damp to both the durability of buildings and the comfort of their inhabitants. |
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Knowledge of why a design was good in terms of damp was possibly less well developed, so that practice was based to a greater extent on experience. We can see examples today of well built designs that have performed well over centuries. But there were probably also buildings that were less well built, and these no longer exist because they had to be demolished.
In the nineteenth century, it is believed that poorer people were allowed to live in newly built houses until they had dried out sufficiently for their 'proper' inhabitants to move in. Such an attitude to damp problems would hardly be tolerated today.
Good thermal insulation is not always beneficial as regards damp. For example, leakage of heat to the ground through older suspended foundations/timber floors can sometimes help to keep damp in check.
Anyone who is making changes to a floor design in order to increase comfort must think very carefully before work is begun. They must also check for unforeseen problems that may arise after the measures have been taken. Turning off the heating during the warm summer months may be devastating for a floor design that has a vapourtight floor-covering.
Experience during the twentieth century and especially since the Second World War make it clear that many problems arise when changes to building practice are made. Some changes can be small and others large.
Examples are given below of changes that affected floor designs in the past and probably contributed to problems with floors: |
- New hygienic flooring materials – easily cleaned but extremely vapourtight – were introduced in the 1950s and 1960s.
Solvent-free, water-soluble adhesives gave better working conditions but had limited resistance to alkalis.
Industrialised building reduced opportunities for drying out.
Incompatible materials resulted in the breakdown of some materials.
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| Limits on maximum moisture content in concrete beam structures |
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When a concrete beam structure is cast, it dries quite quickly on the surface. If it is covered with a vapourtight covering, the moisture in the structure redistributes itself from the damper inner layers to the drier outer layers. It is therefore important to take measurements at some depth into the structure when checking that it has dried out sufficiently before applying the covering.
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| The measurement depth should be: |
- 20% where there is double-sided drying
- 40% where there is single-sided drying
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