Damp Meter Readings – Best Measures

Damp Meter Readings play an important part in finding water leaks and understanding the extent of the damage they have caused. Professional Moisture meters, as they tend to be known in the trade, are highly accurate, sensitive and carefully calibrated instruments.

Damp meter readings are and essential information for a leak detection engineer. There are many different types of damp meter and different readings too. Each are used for different purposes, so professional leak detection specialists are likely carry several and monitor many metrics.

Some with a single purpose to take a specific damp meter readings from, but more often they are capable of being used for different readings and on different materials. Mostly these are non-invasive damp meters / moisture meters. Even those that are not non-invasive, tend to only cause minor impact on materials, most commonly from taking pin readings into materials.

Are Damp Meters Accurate?

As we said earlier, professional damp meter readings are highly accurate. This is very important because they provide essential information to help locate water leaks and to see how much moisture is present. It is important to remember that moisture exists almost everywhere, so critically, we are looking for elevated moisture, especially in comparison to control readings from unaffected areas.

Different materials have different levels of moisture present naturally so what is ‘normal’ for wood could be very different to plasterboard. In fact, different types of wood will have different moisture levels.

This brings us on to…

What is an Acceptable Damp Meter Reading?

The straightforward answer to this is it depends! As we said above, variances in damp meter readings occur for many reasons which is why a qualified leak detection engineer will understand this, it it is an essential skill in finding water leaks. Therefore, when asked ‘what is a bad damp meter reading?’ the answer is the same. Various things come into play on this. We explain this more in our article looking at damp causes and similarly our guide to cold spots.

Things that can affect Damp Meter Readings

• The material being measured – for example, wood, concrete, plaster
• The presence of water / moisture – as you might expect and important for leak detection!
• The time of year – season, weather conditions, outdoor temperature etc
• Internal conditions – heating, temperature, presence of steam from cooking or showers
• Levels of ventilation – from windows, extractor fans in bathrooms and kitchens etc
• The presence of air con or dehumidification – clearly this is like the previous point
• Condition of property – for example, cracks, roof water leaks, level of maintenance
• Construction and age of property – what materials are used, is there a cavity, DMP etc
• The location of the property – for example is it near the sea, a river or lake etc?
• The contents of a property – things like plants, heaters, fans or even people and pets!
• Other items in a property – for example, swimming pools, hot tubs or saunas
• An incident at a property – from water leaks, accidents (bath overflowing!) or flooding
• The presence of rising damp – obvious but it can affect readings when looking for a leak

We could go on but hopefully that helps you understand how these things can affect damp meter readings. If you think about it, if you took two identical pieces of the same material (lets say some wood) and put one outdoors, another in the bathroom, another in the garage and another in the living room – it is very likely that they would have different damp meter readings not necessarily caused by a leak!

Of course all these things can affect each other too in combination which explains why leak detection, damp surveys (including penetrating damp) and water damage restoration is a specialist skill. Buying a cheap (possibly inaccurate) moisture meter, using it in the wrong way, on the wrong materials etc can give misleading information.

What do the readings on a damp meter mean?

There are many different types of reading for many different materials (and various different types of damp) but here are the main types of damp meter readings…

• Moisture Content (MC) – quantity of water, expressed as a percentage of mass, in a material. There are different ways of measuring this for different materials, for example concrete moisture content
• Relative Humidity (RH) – the amount of water moisture / vapour in the air, expressed as a percentage, relative to what the air is capable of holding at a given temperature. This is different to…
• Absolute Humidity (GPK) – the amount of water moisture / vapour in the air, often expressed as the grams of moisture per kilo in the air (GPK = Grams Per Kilo), roughly per meter cubed.
• Wood Moisture Equivalent (WME) – the percent of moisture / water in wood as if it were in equilibrium with with the material you are testing. Effectively this is a measurement within a material as if it was a piece of wood. Perhaps the most complex to understand!
• These readings are taken with pin or pinless moisture meters depending on the area being examined and the material too.
• We have a separate guide as to how different moisture meters are used in different materials such as wood, plaster / plasterboard and concrete in a property.

There are other readings that can be taken, such as vapour pressure, but these are main ones. On the subject of temperature, see our article asking do fans work to cool you in summer.