What does a damp meter reading mean?
If you have had a damp survey carried out, chances are the surveyor used a damp meter. But what does a damp meter reading actually tell you? And what does it not tell you? At South East Timber and Damp, we use meter readings on every survey. Here is a plain English explanation of how they work and why they matter.
What is a damp meter?
A damp meter is a handheld device that detects moisture in building materials. We use the Protimeter MMS2, one of the most advanced meters available for building surveys. It can carry out several different types of measurement, including pin moisture readings, non-invasive moisture readings, relative humidity and temperature, equilibrium humidity in concrete floors, and infrared temperature measurement. It also logs data so we can build up a picture of the moisture pattern across a whole building.
Why damp meter readings matter
The main advantage of a damp meter is speed and accuracy. Readings are non-destructive, so we do not need to take plaster samples or cause any damage to your property. We can move quickly through a building, taking readings in multiple locations. As a result, we can identify where moisture is present and how it is distributed.
That distribution is important. Because the pattern of readings helps us understand the likely cause. For example, rising damp tends to show a characteristic band of moisture at low level. Penetrating damp, on the other hand, often follows a path from a specific point such as a leaking window or a defective gutter.
Why readings alone are not enough
Here is something not every contractor will tell you. A damp meter reading cannot tell you the source of the dampness on its own. It tells you moisture is present. It does not tell you why.
This matters because certain materials and conditions can produce misleading readings. Ground salts, for instance, make a substrate more conductive. This means the meter can record a high reading even when the actual moisture content is not as high as it appears. Similarly, foil-backed plasterboard can sometimes produce readings that look like rising damp but are actually caused by condensation.
In the wrong hands, these readings can lead to an incorrect diagnosis and unnecessary work. This is why experience makes such a difference.
What else do we use alongside damp meter readings?
A good survey goes beyond the meter. At South East Timber and Damp, we also carry out a thorough visual inspection, noting staining, tide marks, salt deposits, and damage to decorations. We use our hands and our nose too, because moisture has a distinctive feel and smell that a meter cannot capture.
In addition, we use FLIR infrared cameras to identify cold spots where moisture is likely to be present. We also use endoscopes where needed, which allow us to look beneath floorboards and into cavities without causing disruption. Together, these tools give us a much more complete picture than any single reading could.
Our meters are also regularly calibrated so that every reading we take is as accurate as possible.
What are the main sources of dampness in older properties?
Once we have gathered all of our readings and observations, we look at the evidence as a whole. In most older properties, dampness comes from one of three sources. First, rainwater entering the building through walls, roofs, or windows — this is known as penetrating damp. Second, moisture rising up from the ground through the structure — this is rising damp. Third, moisture in the air that settles on cold surfaces — this is condensation.
Each of these has different causes and different solutions. Getting the diagnosis right is the most important step.
Want to know more?
If you would like to read more about how damp meters work, we recommend the article by Bryan Hindle on The Preservation Expert blog. Bryan is highly knowledgeable and writes clearly about the technical side of moisture measurement.
If you are concerned about damp in your property, or if you have already had a survey and want a second opinion, we are happy to help. We will give you an honest assessment, explain what the readings mean, and tell you what — if anything — needs to be done.
Get in touch to book a damp survey with South East Timber and Damp. Call us on 01732 884535 or email [email protected].