A Complete Guide to Moisture Meters

The most abundant substance on Earth, and in the human body is water. Though life cannot exist without water, the excessive water content in things like building materials is detrimental and poses safety risks. To measure moisture content in a range of materials, a moisture meter is used. It is one of the essential tools used by carpenters, construction workers and contractors, soil and agricultural scientists, and DIYers of all sorts.

How Moisture Meters Work

A moisture meter takes readings of overall water content and displays findings as a percentage. This can be shown either as a simple number or in the case of high-end meters, with an accompanying indicator scale that changes colour according to measured results. Different materials will have varying optimal ranges of moisture levels. It is the technician’s task to evaluate and interpret the readings. Moisture meters in working order are calibrated, meaning the measured results are compared against a set of expected parameters or moisture scales.

Types of Moisture Meters

There are three major types of moisture meters in terms of how they measure water content:

• Pin-Type Moisture Meters – These use two electrodes or pins that are inserted into the materials being tested. An electrical current passes between the pins and measures electrical resistance. Since water is a conductor, readings with less resistance mean more moisture, and readings with more resistance mean there is less moisture present in the tested material.

Pin-type meters are older designs initially used to measure water content in different types of wood. Today there are models that can also meter moisture content in a variety of materials, including concrete, mortar, cement, plasterboard and others. Although they provide accurate results, they are referred to as ‘invasive’, since to measure moisture they need to pierce into the material surface.

• Pinless Moisture Meters – These are the norm today, and are non-invasive meters that calculate moisture levels by the use of radio waves. The meter sends a set of radio waves at preset wavelengths into the tested surface and scans for any distortions in returning waves. By comparing the two results, the meter then calculates and displays moisture levels.

Both types of meters provide precise measurements, though both have their pros and cons. Pin meters are generally slower; however, they assess how moisture is distributed throughout the material, both at the surface and core. This makes them the better meter for measurements on uneven or irregular surfaces. On the other hand, pinless meters are quicker, can scan larger areas, and don’t run the risk of breaking pins. Their weakness is that they are better suited to flat, solid surfaces.

• Hybrid all-in-one meters use both electromagnetism and electrical resistance to take moisture measurements. They combine both methods of pin and pinless moisture meters. This type of meter allows technicians to quickly scan for any present moisture, and then precisely pinpoint the exact areas and take accurate readings. High-end hybrid models use infrared imaging to locate and visually display any presence of water, then take measurements with either pins or radio waves.

Types of Meters According to Use

• Though most meters sold today can measure moisture levels in a number of different materials and substrates, some provide more accurate readings in one specific type of material. Some of the most widespread types include:

• Wood Moisture Meters measure the moisture content in wood and timber. Normal levels in wood range between 5 to 20 per cent moisture. A wood meter calculates whether the wood is dry, moderately dry, or wet. Some models may also display a colour LED reading in green as dry, yellow as moderate and red as wet, along with the moisture percentage. This allows carpenters, woodworkers or flooring installers to determine whether the material is ready to be worked or needs further treatment. In existing structures, they detect any presence of wood decay, mould or even insect infestations. Most wood meters are the pinless type to avoid unwanted damage.

• Concrete Moisture Meters measure moisture levels in concrete floors, slabs, beams and walls, and are either pin or pinless. Pin-type meters can use longer connecting contact pins or probes that reach deeper into the concrete. These are inserted in drilled holes to determine whether the material has completely dried. Additionally, pinless meters designed specifically for concrete can penetrate up to 50 mm. Most models sold today can also measure water content in wood, vinyl, plasterboard or any materials placed over concrete bases.

• Soil and Plant Moisture Meters are used in agriculture with longer probes set at determined depths in different types of soil. In large farms, if the probes sense lower than desired water levels, the meters automatically activate irrigation and sprinkler systems. When the required moisture is reached for the specific type of crop, the system shuts down.

Features, Pricing and Buying Moisture Meters

Hybrid infrared meters are the most expensive moisture meters, while also boasting the newest tech. Pinless meters are moderately priced and easily accessible, while pin-type meters are generally the most affordable. Besides moisture, most meters measure ambient temperature and humidity levels can be used across a wide range of materials, and are built of durable, high-quality housings. Almost all have smart features, like Bluetooth or Wi-Fi connectivity, in-built memory, and anti-reflective and legible colour displays. All units sold in Australia are pre-calibrated with reference parameters for the material tested. Moisture meters are available from larger hardware stores, while professional-grade meters are sold in stores stocking branded testing equipment.