Moisture Levels And How We Measure Them
Restoration companies that deal with dampness in buildings know that here are several methods they can use to obtain the moisture content levels. Knowing the levels of moisture that is present is helpful when deciding what course of action should be taken when applying damp proof services. The moisture content should be assessed before removing mould from walls and applying damp proof membrane treatments. However, let’s first understand the different expressions of measurement that damp proof contractors are likely to use.
Moisture Content
This is normally expressed as a percentage (%) and this percentage scale is used for wood when a capacitance damp meter is used. Moisture content can also be expressed as a percentage if the material has been tested by a damp proof services specialist using a gravimetric weighing procedure rather than, or in addition to, a capacitance damp meter.
Wood Moisture Equivalent
This is expressed as a Percentage of Wood Moisture Equivalent (%WME). Wood is Hydrophilic which means it is porous, can be soaked and its very structure can affected by water. This is evident when you see wood rot and its inherent strength is severely diminished. Wood will usually absorb moisture relatively easily and this can be measured. Therefore if a damp specialist inserts a wooden dowel into a given building material, the percentage of moisture absorbed by the wood is measured and recorded as Wood Moisture Equivalent (%WME).
Relative Humidity
The dampness in buildings should be compared to the surrounding area and compared against the ambient relative humidity. For example the humidity surrounding a building in a warm, heavily wooded and wet area will likely be higher than in a dryer open space. This relative humidity is expressed as a percentage (%RH). This is used to determine the conditions of the surrounding air against samples taken in dense materials within the damp walls in a building such as brick or concrete. These reading are important as they are measured against the background ambient humidity and that comparison is important.
Degrees Celcius
The most common method of measuring air temperature is the Celcius Scale. Celcius is easy to calibrate as it is done so against the most common substance found on Earth which is water. Water freezes at zero degrees Celcius and boils at 100 degrees Celcius. Temperature is required to obtain the specific temperature of the air or building material in question, so the humidity can be calculated. Warm air can hold more water than cold air. But whether the air is warm or cold, if it is holding half (50%) as much moisture as it could hold when saturated, then the relative humidity is still expressed as 50%. Therefore the temperature is critical to know, as warm air at 50% saturation will be holding more water than cold air, at 50% saturation.
Kilopascal (kPa)
This is the measurement used in recording and expressing vapour pressure where 1kPa is calibrated as being normal. The higher the vapour pressure and the kPa reading given, the wetter the air or building material will be. Because cold air is heavier than warm air you will find that on a cold foggy morning the vapour pressure reading would be relatively high. Vapour pressure is another useful measurement to know when assessing dampness in buildings.
Grams per Kilogram (g/kg)
Grams per Kilogram relates to the specific moisture content of the building material or air within the building. The more moisture that is recoded then the more grams of moisture would be found and this is expressed as a weight. It is helpful to know what the weight of water is in a known weight of building material.
Building restoration companies and damp proofing contractors will be very experienced with all these measurements and terms. It is part and parcel of the damp proof services they provide every day.
Based in Central Scotland, Paradigm Reinstatements is one of the leading specialist building restoration companies in the UK regularly appointed by several of the UK’s leading insurance companies to deal with dampness in buildings, flood damage, damp proof services, fire damage and building reinstatement services in general.
