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The case of 'Salt damp'

Background:
A semi-detached property was reported to be suffering water ingress problems on ground and first floors around chimney areas. Over a period of 12 years this had continually been diagnosed as water ingress via the chimneys/chimney stacks. As a result over £10,000 had been spent to rectify the problem; this included new flashings and even new chimney stacks. Nevertheless the problem still remained.
 

Investigation:
saltdampAll areas of 'dampness' as observed and recorded by an electrical moisture meter were restricted to the areas of the chimney breasts and chimney flues. 'dampness' Some dampness was visible in the form of wrinkling wallpaper and water stains.

Samples of plasterwork were removed for moisture and soluble salt analyses, and these showed a large proportion of chloride in relation to nitrate in the 'damp' areas on all floors. Full moisture analyses further revealed that there was no free moisture present in the removed samples which showed there was no water ingress (this was also following a period of very heavy rain). However, the moisture analysis showed the materials to be quite hygroscopic as a result of the salt contamination.
 

Conclusion:
There was no water ingress: all dampness and spoiling was solely the result of hygroscopic salt contamination of the plasterwork and decorative finish. These were causing sufficient moisture absorption from the air to cause the dampness observed.

The origin of the salts was from the long-term burning of fossil fuels; this was evidenced by the high chloride to nitrate ratio, and their localised distribution around the flues.

Moral: There had probably never been any water ingress. Had a proper investigation been undertaken originally then the huge expenses and building works could have been prevented.

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