Rising Damp & how it can fail your waterproofing barrier

Southside Waterproofing
Aug 12, 2025
3 min read

Rising damp in Australia refers to the upward movement of moisture from the ground into the lower sections of walls and floors through porous building materials like brick, stone, or mortar by capillary action. Most often found in older buildings, particularly a heritage building problem, that either lacks a functional damp-proof course (DPC) - a horizontal waterproof barrier in the wall - or have had the DPC bridged or damaged. It can also affect newer properties however, if their damp-proofing is compromised.

How it happens:

Moisture in the ground is "sucked" upwards through walls - much like a sponge soaks up water - due to the small channels in porous materials.

Signs include:

Damp or musty odours
Blistered paint
Deteriorated plaster
Salt staining (white, fluffy powder)
Crumbling mortar/brickwork,
and sometimes structural weakening.

What does rising damp have to do with waterproofing?

Left untreated, rising damp compromises waterproof barriers - particularly the DPC - by allowing moisture to bypass or deteriorate this barrier through various mechanisms. If the DPC is missing, improperly installed, physically damaged, or has been bridged by renovations or debris, water from the ground can rise through capillary action and penetrate above the intended waterproof layer.

Very important to mention, membraning over rising damp will not fix the problem and over time, all attempts at waterproofing will fail and product warranties could also be voided. Treating the rising damp first and foremost is of utmost importance for all involved.

Once moisture breaches or bypasses the DPC, it can:

Degrade the physical barrier: persistent moisture can corrode or break down older DPC materials (such as slate or bitumen, especially if salt-laden groundwater causes crystallization and expansion, leading to cracking or separation.
Create new pathways: Mortar joints, cracks, or points where the DPC is punctured or discontinuous allow water to move past the barrier, rendering it ineffective.
Facilitate salt migration: rising damp often brings dissolved salts into the wall, which can build up, crystallise, and physically disrupt the structure of the barrier or surrounding masonry, accelerating deterioration.

A compromised waterproof barrier means that moisture can continue to rise into building materials, setting off a cycle of ongoing damage and often requiring replacement or chemical reinforcement of the DPC.

Health risks of rising damp:

Rising damp creates excess humidity and promotes the growth of mould, fungi and dust mites, whish are linked to:

Respiratory problems such as asthma flare-ups, coughing, wheezing, bronchitis, chest infections and in sever cases, conditions like chronic obstructive pulmonary disease (COPD) or aspergillosis (a fungal lung infections).
Allergies: Sneezing, runny or blocked nose, itchy eyes or skin, and aggravation of eczema caused by exposure to mould spores and house dust mites.
Immune effects: Living in damp conditions can weaken the immune system and make you more vulnerable to illness.
Vulnerable populations: The risks are significantly higher for people with pre-existing lung diseases, children, elderly individuals, and those with weakened immune systems.
Excess moisture can also worsen symptoms in those already suffering from rheumatic or musculoskeletal pain.

Addressing damp promptly is important, as ongoing exposure increases severity of health issues.

Southside Waterproofing Supplies is proud to announce partnering with Tech-Dry Building Products and will now stock a range of DPC treatments. Tech-Dry silicone damp-course systems have been installed in over 30,000 Australian properties including private, commercial and important heritage buildings.

Fix rising damp yourself with Tech-Dry's range of innovative products that provide a permanent damp-proof course. Injected into either mortar bed or bricks, Tech-Dry's No More Rising Damp products are backed by a 20 year product guarantee and are formulated specifically for Australian conditions. No More Rising Damp products are used by builders, professional damp-proofing companies and DIY home-owners alike.