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THE COLEMANATOR DAMP DIAGNOSTICS
Moisture and Salt Analysis
As described in the BRE guidance document 245 “Rising damp in walls “Diagnosis and treatment” electrical moisture meters have a valuable role to play as preliminary surveying instruments and will identify areas where further investigation is required. To obtain more conclusive proof regarding the condition of a wall and source of any dampness, the most satisfactory approach is to take samples of masonry and plaster for analysis. This involves extracting via drilling, samples of the masonry material at some depth within the wall. These samples can then be processed to accurately determine the level of moisture and contamination present.
Gravimetric Analysis
The smarter way to measure moisture in building materials
The Gravimetric Analysis procedure is widely regarded as the most accurate diagnostic technique to establish the moisture content of masonry materials and is the only analytical process that is capable of 'quantitive' moisture analysis distinguishing between ‘Free Moisture’ caused by rising, penetrating damp or leaks etc, and ‘Hygroscopic Moisture’ caused by mineral contamination. Together with 'Chemical Salt Analysis' our gravimetric results will provide a more accurate and clearer understanding regarding the origin and quantity of moisture present and the effects of contamination.
'Free Moisture'
'Free Moisture' is exactly that, free water which is not bound to the material and simply occupies space in the capillary pores. This moisture is normally taken into the material via the process of capillarity or diffusion. The term 'free moisture' basically describes the mobility of the water which is free to move in and out of the material. Most dry uncontaminated building materials will usually have very low levels of free moisture.
The free moisture content of a material can however increase due to defects such as rising damp, penetrating damp, lateral damp, condensation and of course escape of water events such as leaks / floods.
'Hygroscopic Moisture'
Most building materials are 'hygroscopic', meaning have the ability to absorb and release moisture in relation to the ambient environment thus, natural hygroscopic moisture levels in building materials do and will fluctuate. The hygroscopic capacity of building materials will also change if a material becomes contaminated with salt. Salts are also hygroscopic, therefore when material becomes contaminated with salts this can increase the overall hygroscopic capacity of the material. Sources of salt contamination include, ground water 'rising damp' chlorides and nitrate salts and ammonia nitrates from chimney soot.
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Contamination of walls and plaster with salts can be problematic. The hygroscopic effects of contaminated material may result in erroneous 'high readings' when materials are tested with electronic moisture meters. This is simply the result of increased electrical conductivity caused by the presence of salt. Salt contaminated materials may also appear damp, even if the source of moisture has subsided. This is simply due to the hygroscopic effect, with the salt laden material becoming noticeably damper during humid/wet periods and less damp during drier periods.
Salt contamination is a form of dampness and may cause plaster and decorations to spoil. Salt contamination is also the most common cause of damp misdiagnosis.
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Chemical Salt Analysis
Walls and plaster ‘not’ affected by dampness will generally have low levels of mineral contamination however, walls and plaster affected dampness such as ‘rising damp’ will often become contaminated 'salt contamination’. This occurs as many sources of dampness in building do not originate from clean water sources. The source of moisture may often result in dissolved mineral salts contaminating the material. Determining the presence, distribution and quantity of salt contaminates can be a significant aid in understanding the origin, severity and extent of the overall damp problem
The Sampling Process
Step 1 - Decide where to take your samples?
RANDOM SAMPLING PROCEDURE
Firstly, Identify the problem area. An electronic moisture meter is usually a good tool to help determine an area of concern but remember, it won't tell you specifically if a masonry material is damp or just simply contaminated. If you are taking samples randomly simply as an aid to diagnosis then remove a sample of masonry or plaster from that location using the procedure described below.
Random samples are normally requested to determine if a particular location is wet, dry or contaminated. Random sampling although useful, does not have the ability to provide with clarity the likely origin / source of moisture . Just simply that the one location tested is either dry, wet or contaminated.
PROFILING PROCEDURE
'Profiling' is the term used when the pattern and/or distribution of moisture and contamination through a structure is mapped and measured. Particular problems often result in definitive trends and the most accurate diagnosis always involves analysis of the trend and a profile of the moisture and contamination distribution.
Profiling is more time consuming to undertake when compared to 'random sampling' however, it is far more accurate when trying to determine the origin of the moisture problem, the level of moisture in the material and the level of contamination.
Before you begin, firstly, decide where you would like to take the profile? Measure the profile across the walls surface using an electronic moisture meter and recorded the profile height.
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Decide on how frequent you would like your samples to be taken over the profile? Normally 100 - 200mm vertical increments is sufficient (depending on the profile height). The higher the profile, the greater the spacing that can be afforded. The more frequent the samples, usually the clearer the trend and data.
See image below, a 700mm damp tidemark and profile with samples taken at 100mm vertical increments upto 1 meter above floor level.
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If you would like to learn more about moisture mapping you may find this article of interest;
Ideally all samples should be taken from the same material i.e. mortar or masonry, although mortar samples are the most consistent. In most cases this will often mean chasing away the plaster to exposed mortar beds as shown in the image above. Where this is not possible it is acceptable to drill the samples 'blind' i.e. directly through the render/plaster to take what ever is beneath, eg, brick or mortar.
Samples should be taken by means of a slow speed drill; use a sharp masonry bit sized between 10-14 mm in diameter. For the best results the sample should be collected consistently from the same depth in the wall. We recommend drilling to a minimum depth of 50% the walls thickness and a heaped teaspoon of sample material (about 5 grams is required as a minimum). Collect the spoil in a small dish or funnel as show in the adjacent image.
Once extracted. Carefully transfer the sample into either a small airtight container such as 35mm film canister or polythene bags; 'Ziploc' bags of 10 -15 cm are ideal. If using polythene bags, 'double bag' each sample and make sure the sample is fully air tight and will not spill open.
Finally, label the sample and record the sample location, height and material. Make sure the label is fixed firmly - do not write directly on the container/polythene bag since this can rub off.
