Fresh vs Saline Water Wetting

Technical research has shown that there are significant differences between fresh water (no salts) and saline water (with salts) wetting. Let's look into the differences between fresh vs saline water wetting.

Fresh Water Wetting (e.g. Rainwater Ingress)

Wetting with fresh water – e.g. rain water ingress – creates a clean, unpolluted water flow with no (or in practice, very low) salt content. Rainwater hits the wall fabric, penetrates it to some extent, then once the rain is over the moisture starts evaporating out of the wall fabric with relative ease as the bonding of moisture to capillary surfaces is not very strong.

Because there are no salts involved during freshwater wetting, there are no crystallizing salts left behind and the masonry will not crumble. Without salts being present, the masonry can undergo hundreds or thousands of wetting and drying cycles without any fabric damages.

Thus, the wetting of the masonry with clean fresh water is harmless, except if the water flow becomes so abundant that it starts washing out salt crystals from the underlying mortar or bricks – then the salt accumulation resulting in damages to the brickwork.

Saline Water Wetting (e.g. Sea spray, Rising damp)

Wetting with saline water – e.g. sea spray, rising damp, chimney leaks etc. – is a completely different matter; with salts in the picture, everything changes.

Salts are solid minerals, which when diluted by water they change their state from solid to liquid. Liquid salts are carried by the water flow up into the brickwork. The ongoing evaporation draws much of the salts to the outer 10-15 mm wall area where they re-crystallize, increasing in volume by 5-10 times (500% – 1,000%). The crystallization pressure can exceed 800 atmospheres, breaking down the plaster, the wall fabric and even concrete – the strongest concrete able to withstand about 550 atmospheres.

Two similar bricks - one salty the other one non-salty - have been subject to hundreds of wetting-drying cycles during  a few months in a controlled lab environment. Within a few weeks the salty bricks started spalling and crumbling, leading to significant fabric damage after only 3 months, as shown in the photo gallery below.

In addition to mechanical damages, the salty and non-salty bricks also have very different properties, both chemical and electrical.

While humidity, during subsequent wetting and drying cycles, can move in-and-out freely of a non-salty masonry (blue band, large movement), humidity variations in a salty wall fabric are significantly less (green band), indicating that a salty wall fabric traps humidity.