The average cellar tank system will cost many thousands of pounds sterling. Keeping groundwater out is the main goal, but how often do we think about naturally occurring internal atmospheric moisture? We ignore this at our peril; Basement tanks and other forms of basement waterproofing can interact with moisture and cause condensation problems… My last article on basement tanks and condensation looked at what condensation is. Condensation occurs wherever humidity and temperature combine to create a “dew point.” So we need to look at those specific factors in a tank basement or waterproofed basement that cause temperature and humidity to come together in this way.

Temperature

Waterproof coatings or membranes are usually not very thermally efficient so they can get cold. And they are usually applied to the inside surface of exterior walls during a basement conversion or basement waterproofing project, making them even cooler. If we put insulation in front of the waterproof membrane, this insulation makes the cold even greater (the insulation keeps the heat in the room and therefore away from the membrane).

heating patterns

If the cellar or cellar is unevenly heated, this can lead to periods when the temperature is too low to prevent condensation.

Humidity

Moisture vapor in the air will move in all directions, so not only does moisture vapor enter a basement or basement from the ground outside, but it also moves from the internal air space of the basement or basement into the outside. An effective impermeable barrier (tank system), designed to be effective against groundwater ingress, will also prevent internal moisture vapor from escaping. Underground rooms are generally more difficult to ventilate due to the lack of windows and doors. Life in general generates moisture vapour, including breathing and perspiring, cooking, drying clothes, boiling kettles using a shower or bath without adequate air extraction all contribute to internal moisture vapour. This in itself is not necessarily a problem. It only becomes a problem if any part of the cellar or basement has a temperature at or below the dew point temperature and the most likely location for this (cold) dew point temperature is the waterproof barrier itself. In my own professional experience, I have seen many cases of cellar conversion and foundation waterproofing projects blighted due to condensation.

In my next article, I’ll look at the damage it can cause, not only to the building’s fabric, but also to the health of the occupants.

In the meantime, to learn more about warehouse storage problems and how to avoid them, click Warehouse Tank.