There are many tools that can assist one diagnosing dampness problems - some of them simple, others more sophisticated. Here are the most common ones we use on a daily basis:
Observation - especially if paired with considerable expertise and a thorough understanding of the underlying phenomena - can be a very valuable tool in diagnosing dampness problems. The look, color and texture of a wall can carry important information to those professionals who understand and able to interpret this information.
On the other hand, visual observation has also significant limitations, direct observation being limited to wall surfaces only, which very often behave very different from the depth of the wall fabric. To gather reliable information from under the depth of the fabric, various tools have been developed.
The most common way in diagnosing dampness problems are dampness meters.
Just like cars - not all dampness meters are created equal. There are many types of dampness meters and depending on how sophisticated they are, they can deliver very different results.
One of the most important quality parameter is of dampness meters is their penetration depth: the deeper a meter can detect moisture under the surface, technologically the more advanced and more costly it is. The opposite is also true: cheap damp meters can only measure humidity on the surface, while more advanced / expensive ones can measure further in depth.
There are 3 different dampness meter technologies in use today. Click on the tabs to open the content.
These meters have originally been developed to measure the moisture content of timber but over the years they have extensively been used to measure the moisture content of masonry.
They have two sharp pins (prongs) as they measure conductivity, measuring the resistance of the fabric between them - hence their name: resistance meters. Because damp materials conduct electricity more than dry ones, the meter can differentiate between various levels of humidity.
Due to their low cost (about £15-20) they became very popular. But having no depth penetration, being able to only detect surface humidity makes them unfit for professional diagnosis - yet they have been used for decades, still being used today.
Capacitance meters are a newer technology and they slowly started replacing old resistance meters. They only have one larger electrode, which sends a small current into the wall, and based on the capacitance of the material (its ability to store energy) the meter calculates the wall fabric's moisture content.
Being a more advance technology, capacitance meters are more expensive (about £100-300) but also more reliable as they can penetrate about 20-40 mm in depth, giving a much more reliable moisture measurement than resistance pin meters.
Microwave meters are the latest technology developed during the past 10 years or so. They work on the principle of ground-penetrating radar: the meter shoots a microwave beam into the wall fabric reading its reflection. As damp areas absorb microwave beams more than dry areas, the meter can differentiate between different moisture contents.
Microwave dampness meters, although less known, they are finding their way into the professional standards of more and more European countries. These meters offer some major benefits in comparison to other meter types, being:
The downside is high cost. Depending on configuration, accessories and software options they can cost anywhere between £1,000 - £3,000 so only professionals can justify the cost. Bundled software solutions permit further in-depth analysis of the wall fabric including the creation of moisture distribution charts to visualize the moisture content of the fabric at various depths.
Here are some samples images of the in-depth analysis of microwave moisture meters.
It is important to understand that each dampness meter technology has its limitations. Although they can be great tools that allow professionals to "see" beyond the surface, they should be used in conjunction with other observations and measurements.
The practical experience of the surveyor is also very important; an experienced ones can much quicker correlate the various data obtained from various sources, to come up with an accurate diagnosis.
Drilled-core analysis, also known as gravimetric analysis (gravi-metric = weight-based measurement) is the most accurate filed-based moisture measurement method, which is considered the "golden standard" worldwide.
This is what English Heritage says about gravimetric analysis in their conservation handbook Practical Building Conservation: Mortars, Renders and Plasters, which is used as reference guide by many conservation specialists throughout the country.
Gravimetric analysis of a drilled sample is the most accurate of the analytical methods, and it is therefore used for calibrating other forms of measurements.
English HeritageThe moisture content of the masonry is determined from drilled powder samples taken from the depth of the wall using a small diameter masonry drill, a precision scale and drying oven. Each wall sample is first weighted (wet weight), dried, then weighted again (dry weight). The weight loss is the evaporated moisture content of the masonry explained in percentages.
Gravimetric measurements, although very accurate, require dedicated instrumentation (gravimetric scale) which is not cheap. They can cost anywhere between £1,500 - £5,000. We have invested in several of these scales, all of our surveyors and engineers having their own equipment, being able to do accurate moisture tests and diagnosis on the spot.
Gravimetric analysis is an improved, more accurate version of the older calcium carbide test.
In addition to moisture measurements, salt measurements can give building professionals important information about the origin and type of moisture. Salts are hard, crystalline materials, which can temporarily be dissolved and carried into the masonry by water. Depending on their physical-chemical properties, different salts are deposited in different parts of the wall fabric - higher vs lower, deeper vs near surface. Some salts are known to primarily originate from the ground, while others from other sources, this giving important information about the source of moisture that might have carried them into the wall fabric.
We perform the chemical analysis of the most important salt types, which account for over 98% of all masonry damages. These are:
Borescope or pinhole cameras can be very useful as they can provide valuable information from hard to access spaces. This can include the condition of the wall cavity, the composition and structure of the walls (e.g. in case of rubble infilled walls), the underfloor area for inspecting the condition of the floors and joists, or for tracing leaks and building defects.
Thermal imaging or infrared (IR) cameras have been used by quite some time for masonry diagnosis. Infrared cameras visualize changes in surface temperature and can be used to detect thermal bridges (areas of heat loss), leaks, moisture and water infiltration etc. Damp areas are generally cooler than dry areas and this temperature change can be picked up the thermal imaging camera and provide us additional information.
In addition to the measurements listed here we also perform other tests and measurements to solve specific situations.
Whatever your dampness problem is, we are likely to find its root cause which opens the road to resolution. We also like complex and challenging cases, so far we have solved them all. :-)
If you have a dampness problem and need some help or guidance in diagnosing it, please get in touch, one of our friendly surveyors will get back to you.
Here are some other related pages that you might want to read to broaden your knowledge in this field.
Here are some of our projects where we have dealt with some of the issues discussed on this page:
Here are some photos demonstrating these concepts. Click on any image to open the photo gallery.
Drilled core measurements are considered the most accurate form of dampness measurement. Despite its slightly invasive nature that involves a small amount of drilling, it gives one a very accurate picture about the moisture content of the masonry.
The latest moisture measurement technology – microwave moisture meters – allow for non-invasive deep moisture detection in the masonry. Using specialized software accompanying these meters, one can visualize the moisture content of the masonry.
Here are some real-life measurements from various buildings. Red areas are damp, yellow/green areas are moderately damp, while dark blue areas are dry.
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