Gravimetric Analysis

Gravimetric Testing For Dampness in Buildings in Yorkshire, York, Harrogate and Scarborough

Laboratory analysis services

Gravimetric testing for dampness is the process of establishing the true water content of a material sample differentiating between the two different sources of moisture which make up a materials total moisture content. A materials total moisture content is the sum of its capillary moisture often referred to as free moisture introduced from issues such as; rising damp, penetrating damp and water leaks. The other part is its hygroscopic moisture content which is the materials ability to absorb moisture from the air often increased through contamination.

The Gravimetric process is widely accepted as the most accurate process for establishing the true moisture content of a material sample and determining its moisture composition as described in BRE 245 ‘Rising damp in walls: Diagnosis and Treatment’.

Unfortunately, this process is disruptive, meaning samples of the structure need to be removed for analysis and profiling and because the procedure involves the use of specialist equipment the process must be undertaken off site in a scientifically controlled laboratory.

The samples are weighed and then exposed to a series of different environmental conditions before being weighed again at each stage. This allows a weight measurement of water uptake or loss at each stage to be converted to a percentage of water differentiating between free and hygroscopic.

Gravimetric testing is the only procedure with the ability to differentiate between free and hygroscopic moisture providing us with a deeper understanding into the moisture and salt distribution through a structure.

With the ability to identify exactly how much water is attributed to free moisture and hygroscopic, including where exactly the moisture is distributed through the structure, we can accurately advise if a problem is persistent or historic and what remedial action is any, is required.

Gravimetric testing for damp is ideal for use in the following circumstances;

  • To differentiate between rising damp, penetrating damp and condensation
  • To determine the profile of moisture
  • To determine the quantity of salt contamination
  • To determine the distribution of salt contamination
  • Historic buildings
  • Where there are high levels of contamination
  • Where a dispute arises

Our professional and credible damp surveys are only undertaken by experienced and fully qualified surveyors who hold the National Qualification for remedial surveying C.S.R.T. awarded by the BWPDA / PCA, our industry body. This proves that our surveyors have been independently examined and tested, proving their extensive knowledge and expertise.

All of our surveys are carried out in accordance with The British Standards Code of Practice.

To learn more about our damp proofing systems, practices or what's involved in a damp survey read up on our blog posts:

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Want to know more about testing for Damp?

Sometimes it is necessary to understand more about a building and how moisture moves through a structure other than the information simple none destructive tests provide. Surveys for damp are often conducted using none destructive techniques and instruments such as; visual observations aided with electronic moisture meters. This is fine and totally acceptable especially in a pre-purchase scenario. Most experienced surveyors will be able to use these none invasive techniques to establish a good understanding about what is happening within a building.

moisture meterNone invasive electronic moisture meters however, do have their limitations. Most of these sensitive instruments are calibrated to be used on timber meaning when they are used on masonry and plaster, readings taken are not quantitive and accurate, they can only provide an equivalent of wood value. In addition, as electronic moisture meters mainly measure resistance they can also be affected by other building materials, minerals and salts. In some scenarios their results may be affected by a conductive material providing a higher than acceptable reading, which to the inexperienced could result in miss-diagnosis.

To learn more about electronic moisture meters read our blog here:

calcium carbide meterThere are other onsite investigations which can provide a deeper understanding and more accurate moisture content analysis of a building such as the speedy test performed with a calcium carbide meter. Undertaking this investigation is however disruptive which involves removing samples from the structure for analysis. As an onsite method of investigation, this method is quick, easy and is one of the most accurate, although again this test procedure also has its limitations.

The problem with a calcium carbide test is the process will only measure the total moisture content of a sample and is unable to differentiate between potential hygroscopic moisture loading and free moisture. This would present a particular problem when examining older properties particularly those with a history of damp where contamination is evident. Again, if the results of calcium carbide test are interpreted incorrectly, could result in the unnecessary expense of repair where not necessary.

To learn more about calcium carbide meters read these articles on our blog:

The most accurate way to differentiate specifically between the hygroscopic moisture and free moisture is gravimetric testing, a process referred to in the BRE document 245 ‘Rising damp in walls: Diagnosis and Treatment’.

gravimetric measureGravimetric analysis however is not a site-based method of testing. This process requires specific laboratory equipment and involves taking masonry samples throughout the subject structure. The samples are weighed and then exposed to a series of different environmental conditions before being weighed again at each stage. This allows a weight measurement of water uptake or loss at each stage which can be converted to a percentage of water.

gravimetric testingGravimetric testing is a precise and complex procedure which isn't instant, the whole process takes a couple of days to establish however, the results will provide the differential between hygroscopic and free water content within each sample.

If you would like to know more about damp investigations, please feel free to read through our blog or contact us.

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