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Salt in the damp moisture will actually cause a microscopic attack on the masonary materials. As moisture evaporates, the salts will crystallise. This process causes pressure in the masonary that surrounds each salt crystal. Over time , and as the process repeats itself, masonary will break down in layers. Some specific salts will even cause a chemical reaction that will also destroy the internal structure of masonary materials.

Salt Damp - The Issues

An electrical moisture meter when used will respond to small amounts of moisture and certain salts. In building materials theses salts are hygroscopic , which means that they absorb moisture from the surrounding atmosphere. If the atmoshere is of high humidity then the greater the amount of moisture is absorbed. The greater the concentration of salts as well will result in a greater absorption of moisture. If a wall is contaminated with salts and a lack of free moisture there, the wall will appear to be dry visibly. But if tested with a moisture meter you will get a high moistent content reading. If contamination is high and has got in to any decorative finishes, at times a wall can look very damp solely because of moisture absorption from the air. This is what salt damp is.

How it looks though is dependant upon the surrounding humidity and whether or not the salts get in to the finish of a wall. With standard wallpaper this easily occurs as salt damp is permeable. With vinyl wallpapers, dampness is rarely visible as the surface is relatively impermeable. Vinyl wallpapers will tend to bubble as the adhesive behind it softens and the paper backing expands.

A quick way to check if you have salt damp is to peel a small area of wallpaper back and allow it to dry in the room. If the adhesive is still sticky after about 30 minutes then its highly possible there is a salt damp issue going on in your walls as the adhesive is kept soft by salt contamination.

The main issue with salt damp is that it is not always visible. Visibility is down to the humidity levels. If there is not moisture to absorb from the air (low humidity) then surfaces will appear dry and to have no issue.

Salt Damp

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Salt damp is the term used to describe the damage done to buildings by the destructive action of salts and moisture.

Damage to buildings can be as minor as bubbling paint, fretting mortar and plaster to actual serious decomposition of complete walls.

Salt damp in walls is mostly caused by rising damp. Rising damp will occur when the damp proof course is ineffective and allows moisture to rise from the ground and soak upwards in to walls by capillary action.

If the ground moisture is high in salts then a high salt content will rise in to the walls and pose a serious damage threat. If the building walls have been sealed then the salt damp will simply climb higher and higher to a level where it can evaporate.

Salt damage is caused in 2 principal manners. The presense of the damp will cause materials to deteriorate. Materials like plaster will soften and crumble, paint will begin to peel off walls and any metals such as nails will begin to rust.

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Prevention Better Than Cure

It is better to prevent a problem occuring, than having to deal with a problem. So to prevent the possibilites of salt damp one should;

Improve site drainage and landscaping as well as they can in order to deflect rainwater and any underground water away from your building. You really want to protect your walls against any water attack.

Get rid of deficiencies in the design of the home that allow rainwater to hit your walls.

If possible try to improve any under floor ventilation. Good ventilation here will reduce levels of moisture reaching your walls.

Always keep a building well maintained. If the roof leaks, fix it! If the guttering leaks or overflows, fix the issue! You dont want to allow any unnecessary moisture to get in to the walls.

Get nature on your side. Coatings and membranes on your walls can prevent moisture evaporation. Remove these coatings and allow nature to reduce the moisture levels in your walls.

Silicone Injection Treatment

This is cost effective and less intrusive than other treatments which require the removal of bricks and inserting damp courses.

With this treatment holes are drilled in the wall and damp proofing liquid is pumped in. This liquid then proceeds to absorbed in to the brick or stone by capillary action. These bricks or stones that absorb the liquid, become a part of the damp course.

The best time to treat salt damp is in Spring or Summer as the whole process takes about 6 months because once the silicone barrier has been created, the walls need about 6 months to dry properly and shed the salt.