Salt Damp & Chimney Breasts

“Chimney salting”; refers to a condition where white, powdery deposits appear on the surface
of a chimney. This is usually caused by efflorescence, a process where water within the
chimney’s bricks or mortar brings soluble salts to the surface as it evaporates.

When moisture penetrates the chimney structure—either through cracks, porous bricks, or
from inside the house—it dissolves salts present in the materials. As the water moves to the
surface and evaporates, it leaves behind these salt deposits, creating a white, crusty residue.

Why is it a problem?

Moisture Issues: The presence of efflorescence indicates that there is too much
moisture in the chimney. Over time, this moisture can lead to more severe issues like
mould growth, deterioration of the brickwork, or even structural damage.

Aesthetic Concerns: The white staining can make the chimney look unattractive.

Hygroscopic salts the aggressive salts that migrate via chimney breasts have the
ability to absorb moisture from the air. This property makes them “hygroscopic,”
meaning they can attract and hold water molecules from their surroundings.

Condensation: When there is an imbalance in internal atmospheric conditions,
condensation will be attracted to areas containing hygroscopic salts.

How to address it?

Fix the Moisture Source: Identifying and eliminating the source of moisture is
crucial. This could involve repairing cracks, restoring mortar joints (also known as
pointing) improving ventilation, or installing a chimney cap.

Cleaning: The salt deposits can be cleaned off the surface, but if the underlying
moisture issue isn’t resolved, the problem will likely return.

Specialist Replastering: In order to control the passage of these aggressive hygroscopic salts, replastering will be almost always be required.

In summary, chimney salting is a sign of moisture problems in a chimney, and addressing it
involves both treating the symptoms (the salt deposits) and the underlying cause (moisture).

Salt Damp

“Salt damp” refers to a specific type of damage to buildings, particularly masonry structures,
caused by the presence of salts within the walls that are activated by moisture. This problem
is common in older buildings, especially those built with materials that are susceptible to
moisture absorption.

How Salt Damp Occurs:

1. Moisture Penetration: Water enters the walls of a building through various means,
such as rising damp from the ground, rain penetration, or condensation.

2. Dissolution of Salts: The water dissolves salts that are naturally present in the soil or
within the building materials like bricks or mortar. These salts are often sulphates,
chlorides, or nitrates.

3. Movement of Salts: As the water moves through the wall, it carries the dissolved
salts with it. When the water reaches the surface and evaporates, it leaves behind the
salts.

4. Crystallization and Damage: These salts crystallize as the water evaporates, often
just below the surface of the wall. This crystallization can cause the surface to flake,
powder, or even crack, leading to visible damage known as “spalling”.

Common Signs of Salt Damp:

White, Powdery Deposits: Similar to efflorescence, you’ll often see white, powdery
salt deposits on the surface of the walls.

Flaking or Peeling Paint/Plaster: As the salts push towards the surface, they can
cause the paint or plaster to bubble, flake, or peel away.

Crumbled or Weakened Bricks/Mortar: The crystallization of salts within the
bricks or mortar can cause them to break down, leading to structural weaknesses.

Preventing and Treating Salt Damp:

Moisture Control: The key to preventing salt damp is to control the moisture
entering the walls. This could involve improving drainage around the building or
repairing the external fabric of the building.

Removing Salt Deposits: If salt damp is already present, the affected materials may
need to be removed and replaced. In some cases, special treatments can be applied to
neutralize or block the salts.

Using Salt-Resistant Materials: In areas prone to salt damp, using materials that are
less susceptible to salt damage, or applying sealants and barriers, can help protect the
building.

Salt damp is a significant issue because it not only affects the appearance of a building but
can also lead to more severe structural problems if not properly addressed.

Do you have a damp chimney breast or areas of salting in your property?
Avant Garde Damp Solutions have been caring for properties since 2003, and are your
reliable local experts. We’re one of the most established damp proofing companies for
London and the Home Counties, delivering affordable and tailored solutions across the area.
Simply get in touch for some professional advice.