Fact: rising damp is not condensation.

Rising damp is a combination of several phenomena, condensation just being one of rising damp's sub-stages. (shown on stage 3)

Water vapours move into the dry capillary and get deposited onto the capillary walls, initially as one single layer of water molecules, then multiple layers, gradually leading to condensation, the formation of a liquid film on the capillary surface. This eventually develops into a capillary flow.

Condensation is just one of rising damp's sub-stages

Two Distinct Phenomena

Rising damp and condensation are two different phenomena, as shown in this German technical book.

Various phenomena: Penetrating damp - Rising damp - Hygroscopic (salts) moisture - Condensation

Rising damp is the migration of water from the ground up, through the wall fabric due to capillary suction, then evaporating into the living environment. The water moves AWAY (evaporates) from the wall as it evaporates into the living environment.

Condensation occurs when humidity from the air gets trapped by cold surfaces and liquefies. The water (vapors) move TOWARDS the wall fabric from the environment.

These are completely opposite flows - different phenomena. Here is the scientific explanation of the differences between the two - by Dr. Roberta Giorio from Center Materials Research (CMR), Vicenza, Italy.

Some Comparative Figures

Let's look at some figures for condensation. An area with high humidity contains about 10-12 grams/m³ water vapors, which is known as absolute humidity.

This, for a 30 m³ room translates to about 300 - 400 grams of water, which is about 10X less water volume then the amount supplied by the forced evaporation regime of rising damp, which can easily evaporate several liters of water per day from a few meter long wall section.

Evaporation as a result of rising damp in an abundant flow, which can amount to several liters per day. Condensation on the other hand is a much less significant flow, resulting in much less water flow (over 10X less) than rising damp.

This logically makes sense as the moisture quantity of the air is significantly less than the moisture quantity of the ground, which can draw from the water table an unlimited quantity of water. So the main source of moisture is the soil (rising damp), not the air (condensation).

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