Hygroscopic Salts

Dealing with Hygroscopic Salts: Expert Guide to Fixing Damp Walls



What Are Hygroscopic Salts?

Hygroscopic salts are compounds that absorb moisture from the surrounding environment. These soluble salts are often visible as tide marks on plaster, brickwork and exterior walls. These marks are caused as nitrates and chloride become concentrated where water evaporates out of your wall.

So, by their very nature, hygroscopic salts can only be present when there is some form of excess moisture. Older buildings may be prone to damp, but salt stains are certainly not exclusive to them. In certain circumstances, salt marks can appear on walls in any type of building that may have damp patches.

What Can Cause Salt Marks On A Damp Wall

Rising Damp

Rising damp occurs when groundwater or inadequate drainage from waterlogged gardens ascends through walls, especially in structures without proper damp proofing.

This can lead to the formation of hygroscopic salt deposits on interior walls.

Penetrating Damp

Penetrating damp occurs when rainwater or external groundwater permeates through inadequately protected surfaces, introducing salts into the building materials.

This can cause damp patches and salt deposits on walls.


Leaky guttering, cracks in brickwork or mortar combined with a lack of damp proofing can cause rainwater and salts to soak through the porous materials. This can again cause a damp wall and salt marks.

Additionally, new build houses take up to 12 months to ‘dry out’ after completion and often have salt marks on the exterior walls for a minimum of a year. This is commonly known and not to be concerned about

Faulty Plumbing

Problems with plumbing that leaks or causes flooding can lead to damp which can occur on any surface. If not allowed to dry out effectively, this can lead to hygroscopic salt creating stains on walls, floors and ceilings.


An environment that is too humid can cause condensation and damp walls leading to paint and plaster damage and hygroscopic salt stains.

Identifying Hygroscopic Salts in Walls

Visible Signs and Testing

Visible signs of hygroscopic salts include white marks or stains on walls, damp patches, and efflorescence.

Most professional damp surveyors will be able to identify hygroscopic salts by sight and with a little further information on the history of the building and location. Testing with damp meters and plaster sampling can help determine the presence of hygroscopic salts by the presence of nitrates and chlorides.

Effects of Hygroscopic Salts on Building Materials

Damage and Deterioration

It is important to understand that the mere presence of hygroscopic salt on your wall indicates that there is already a pre-existing issue present. It is important to get the correct advice on potential issues such as rising damp, penetrating damp or any other persisting case of damp and excess moisture. Even without the salt deposits, these problems can cause structural damage and should be dealt with immediately.

Hygroscopic salts can compromise the structural integrity of building materials. They absorb even more of the moisture than damp alone and rise through the masonry, plaster and other porous surfaces leading to various forms of damage over time. This includes degrading mortar and plaster, corroding metal elements, and causing surface crumbling and spalling.

Properties of Hygroscopic Materials

Hygroscopic materials are substances that attract moisture and then trap it within. A great example is the silica gel packets placed in pockets of new clothing and handbags. They are specifically designed to prevent moisture contamination from damaging clothing and materials.

Other examples are honey, glycerin, ethanol, methanol, concentrated sulphuric acid, and concentrated sodium hydroxide.

How Hygroscopic Salts Impact Air Quality

Increased humidity, condensation and excess moisture can have an impact on the quality of the air in your home and therefore, prevention is key. Dampness can cause health problems such as respiratory issues and irritate allergies, particularly for those with underlying conditions that are triggered by humidity, such as asthma. You can read more about the health risks of damp and mould here.

However, it has been know that hygroscopic salts, when used correctly, can actually lessen humidity levels when used as a dehumidifier.

Damp Proofing and Removal of Salts

Eliminating Moisture Sources

Fixing plumbing leaks, improving drainage, treating rising damp and addressing condensation issues can help eliminate moisture sources that contribute to hygroscopic salts.

Installing or improving damp proofing can prevent the upward movement of moisture through walls.

Treating Salt Deposits

Brushing or vacuuming visible salt deposits can provide a temporary solution, but does not address the underlying issue. Professional interventions, such as applying salt-inhibiting coatings or replacing damaged building materials, may be necessary for a comprehensive solution.

Prevention and Maintenance

Improving Building Materials and Construction

Choosing building materials carefully and ensuring proper construction practices and damp proofing can help prevent hygroscopic salt issues.

Regular inspections and maintenance can help identify and address damp problems before they wreak havoc on a property.

Regular Inspections and Maintenance

Regular inspections can help identify signs of dampness and hygroscopic salts, allowing for prompt treatment and prevention of further damage.

The Property Care Association recommends regular inspections and maintenance to prevent damp problems.


By understanding the causes and effects of hygroscopic salts, and taking preventative measures, property owners can ensure the longevity and health of their buildings. Dealing with hygroscopic salts requires a comprehensive approach that addresses the root cause of the issue, rather than just the symptoms.

Contact Damp Surveyors Ltd today for a professional to detect signs of damp, such as rising damp, penetrating damp, and many other types of damp. The damp survey is performed by trained, experienced, approved and qualified damp surveyors to spot the early signs of a damp problem on any building.

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Picture of Sam Fitzgerald – CSRT Damp Surveyor

Sam Fitzgerald – CSRT Damp Surveyor

Author – CSRT Damp Surveyor
Sam is a highly qualified and seasoned damp surveyor with over ten years of specialised experience. With a strong academic foundation in building surveying and numerous professional certifications, Sam has established himself as an authority in the field of damp diagnosis and remediation.

At Damp Surveyors Ltd, Sam applies his extensive knowledge to help homeowners across the UK address and solve their damp issues effectively. His approach combines cutting-edge techniques with a commitment to honest, client-focused service, ensuring that every survey and recommendation is tailored to the specific needs of the property.

As a thought leader, Sam’s insights into damp prevention and treatment have been featured in industry publications, underscoring his role as a trusted expert dedicated to maintaining the integrity and comfort of your home.

Testing device for measuring dampness in a house


At Damp Surveyors Ltd, we stand out as your premier choice for damp survey services in the UK. Our commitment to excellence and customer satisfaction sets us apart. Here’s why you should choose us:

  • Exclusive 3 Free Quotes: We offer a one-of-a-kind optional service where you not only get our top-notch damp survey but also receive 3 free quotes from vetted local companies, giving you peace of mind by saving you thousands on getting the most competitive quotes, and also time researching and contacting other reputable companies.
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Choose Damp Surveyors Ltd as your reliable partner for all-inclusive survey needs. Our top concerns are the health and safety of your property, and we are committed to providing outcomes you can trust.

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