Salt – Good on Food but Not On Walls

Roof restoration
February 12, 2018 Wall protection

Too much salt on food is not good for you – and the same applies to walls.  Ever spilt some red wine onto your table cloth and grabbed for the salt cellar to stop the stain setting in?  The salt sucks up the wine because it is a hygroscopic element – a substance that absorbs moisture.

The main cause of salt on walls is damp. Stains on walls, or salt damp as it often called, becomes evident as spot bubbling paint, powdery plaster or fretting mortar and in some cases particularly in older homes decomposition of the wall materials entirely. It is also referred to as efflorescence which actually means blooming. Those unsightly deposits are in fact salts blooming on the surface of your walls.

Indications of Salt Damp or Efflorescence

The white deposits are formed by a reaction between water and the natural salts that are present in most construction materials. These salts are dissolved by water and then make their way out of the material as the water evaporates. Water will find a way out of anything, and in homes it can manifest itself along with the salts in white crusty deposits on the surface of plaster, bricks, floors, etc.

Causes of Salt Damp

The prime culprit in salt deposits is rising damp. If the soil is high in salts in your area, then the rising damp will exacerbate the problem. If your walls were originally sealed, the damp will bloom up the wall until it is able to evaporate.  Remember water will always find an outlet.

The damp proof course (DPC) that was in the wall could be operating ineffectively and not stopping the capillary action of the ground water from getting into the home.

Salt damp damage

The appearance of a tide mark of damp will occur.

Damp will lead to deterioration, seen in the flaking and bubbling of plaster, rotting of wood, peeling of paint, rusting of steel, etc.

Mould could grow and mustiness will develop leading to unhealthy, and smelly, conditions, rather like a compost heap though not as beneficial.

Termites love damp, so beware of these destructive creatures if you have a damp problem.

When moisture evaporates below the surface, crystallisation of the salts occurs and this microscopically affects the building materials by a type of erosion. As the cycle repeats further breakdown occurs until layers start to peel off.

You have identified salts being extracted onto the surface of your walls – what do you do then?

Identify the source of the damp

Inside the home, the actual efflorescence process is not really damaging the wall, but you are not able to decorate if it exists – it will cause damage to the paint or wallpaper that you may want to apply. Outside the home, salting on the surface will not look attractive. It’s a grubby, unfinished look. Not good for resale or for keeping your home looking spick and span!

So, the extent and causes of this salt build up need to be examined. We know that generally the main culprit is rising damp.

A simple salt damp formula to follow:

Salt build up = existence of damp = high likeliness of rising damp as being the culprit 

However, there are other causes or sources of damp and these need also be examined prior to spending a fortune on trying to fix the problem.  These could be many.

Some examples other forms of damp could be:

Defective flashing on the roof

Uncapped chimney

Leaking roof

Plumbing leaks

Defective guttering

Defective drainage

Too high ground levels around the house

Condensation within the house

Poor drainage in a garden bed that is too close to the house.

Common sense will tell you if you can do it yourself or if you need an expert to:

  1. a) Find the cause/s
  2. b) And then identify the treatment

How to Solve the Salt Problem in your Home

Normally, efflorescent salt is apparent in fairly newly built homes if the proper protection procedures for protecting the brickwork were not followed during constructed. This allows water to ooze out the porous bricks and leaving behind a salt residue. An easy solution is to allow the affected area to fully dry off and then simply brush the salt off the wall with a wire brush, for the exterior walls, and use a sponge on the interior walls.

Sometimes re-plastering may be required.

Try and reduce or redirect all moisture at its source without causing a major restructuring of the home.

Look into utilising membranes that will create a physical barrier to the damp.

Consider damp proofing materials to re-damp proof.

Use chemical damp proofing, such as water repellent.

Back to DIY basics

Good maintenance and housekeeping habits will solve the salt problem before it starts.

So be vigilant and check the sources of possible damp and fix them. Allow evaporation from the walls by reducing unnecessary coatings and membranes and remember you don’t want your guests to say: “Nice people, shame about the smell.”

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