For many people, the discovery that there is damp in a property comes from a HomeBuyer Report. Up until 2009 this was known as a HSV (Homebuyers Survey and Valuation). It’s often still referred to as a Homebuyers Survey. It is the most commonly undertaken type of survey which looks at the general condition of a property and is designed to give professional advice so that homebuyers can make an informed decision about whether to proceed with the purchase of a property. A HomeBuyer Report is probably best described as a ‘light touch’ survey. For example, the wiring in a house isn’t checked and surveyors won’t even lift floorings up to investigate potential issues. The survey is aimed to spotlight urgent and substantial issues that need addressing or suggest further investigation, such as damp. And evidence of damp will not be investigated in any great detail – it will just be identified through damp meter readings.
Of course, you can buy a damp meter yourself if you want to investigate whether there is damp in a property. Here’s a guide to the things you need to know about using damp meter readings to find damp in a property.
What types of damp meter are there?
There are three main types of damp meter that are used to identify levels of moisture or damp within a building structure: carbide moisture meters, laboratory testing meters and the most common type (and the one that could be described as a conventional damp meter), an electrical resistance meter.
The trade name most commonly associated with professional surveyors is ‘Protimeter’. Protimeters are the most advanced form of electrical resistance meters. As they are the ‘professional standard’, they are more expensive, but with the higher price tag comes a range of advanced capabilities and special attachments.
Electrical moisture/damp meters
Essentially, the vast majority of electrical moisture or damp meters work in the same way and look quite similar. They tend to be small, handheld devices that are battery powered and feature two prongs at the top of the unit.
Damp meter readings are gained by pressing the two prongs into a substrate. An electrical current is passed through the prong and any moisture that is present is transmitted to the second prong. The meter then measures the resistance to the passage of the current between its two prongs. The higher the current that passes, the lower the level of measured resistance will be.
The results, usually displayed digitally on the screen of the meter, and is given as the percentage of moisture content within the surface being tested. Some damp meters use a gauge system instead – with green turning red if there is a high damp percentage found – and some have a warning sound that gets louder with the level of moisture found.
One thing worth considering is that most damp meters are actually calibrated primarily to determine the level of moisture within timber – although they do provide a reasonable indication of the level of damp within the likes of brick and plaster too.
Protimeter Diagnostic Meters
Because of the fact that most electrical moisture meters are most accurate in giving damp meter readings for timber. The most useful types of damp meters are those that measure both the moisture content in timber. the relative moisture, and are able to determine dew point temperatures and humidity. This type of damp meter is described as being ‘protimeter diagnostic’. These types of damp meters are commonly available and very popular, typically they are small, light and user-friendly.
Drawbacks of damp meters
Damp meters do sometimes get a bit of bad press. To be more exact, the way that some surveyors use them to obtain damp meter readings is often criticised. In a HomeBuyer Survey, it is common for the surveyor to carry out a few, fairly random, damp meter readings at different sections of a wall. If the readings are high, the surveyor will not usually investigate this further, but they will reference the evidence of damp in their report. This means that the potential homebuyer will have no real choice but to pay for a damp survey, slowing down the process of purchase.
Although, in general, damp meters are very useful and give reliable damp meter readings, sometimes results can be distorted and skewed somewhat. This is most common when the prongs of the meter come into contact with other materials. Therefore, salt content in older structures or metal beading can give an unusually high (and ultimately a false) reading. Aluminium-foil backed plasterboard is another substance that can affect the reliability of damp meter readings. This type of issue is demonstrated in this video:
For more information about some of the most popular devices that will give you damp meter readings, Click Here For a list of products and reviews.