Welcome to our blog.
I was surprised to find that there is still no blog about the issue of Rising Damp.
In general, from experience we can say that if a house is older than 30 years, the Damp Proof
Course (DPC) installed during construction usually no longer works. Of course, a lot depends
on the location, water saturation of local soils, materials and thickness of walls, foundation
type, etc.
Below we will look at an example of a classic situation with rising damp. Both houses were
built more than 30 years ago, which means that DPC installed by builders collapsed from time
and ceased to perform its function – preventing damp penetration from soil up the walls.
In both houses, the walls are double brick, cement-sand rendered.
Rising Damp: This happens when moisture from the ground rises through the walls due to
capillary action. This water contains salts that also pass through the wall.
Render and paint can deteriorate, and wallpaper can usually be cleaned. A visible spot in the
form of a tide often appears on the wall at the point where it has reached the groundwater.
Waterproofing Melbourne | Internal Wall Waterproofing | Damp Proofing | Rising Damp | Waterproofing Rising Damp
| Internal Waterproofing | Lateral Damp | Garage Waterproofing | AWC Group| Penetrating Damp | Crack Injection |
External Waterproofing | External Wall Waterproofing
You can also see how the salt bloomed inside. This is often associated with increased humidity
and leads to the separation of paints and even plaster. Externally, the mortar may crumble,
and white salt spots may appear on the walls.
When the work is done from the inside, as in this case, we try to install the chemical DPC as
low as possible. Usually this is the first mortar course of the brickwork above the floor. To do
this, we need to remove the existing render by a minimum of 200 mm from the floor to open
the brick and be able to see the first course from the floor.
The manufacturer of Damp Proof Course Cream recommends removing all damp-affected
render + 300 mm up. This is discussed with the customer before starting work.
Waterproofing Melbourne | Internal Wall Waterproofing | Damp Proofing | Rising Damp | Waterproofing Rising Damp
| Internal Waterproofing | Lateral Damp | Garage Waterproofing | AWC Group| Penetrating Damp | Crack Injection |
External Waterproofing | External Wall Waterproofing
After the render is removed, it is necessary to drill holes in the mortar courses every 80 mm.
The hole should not be drilled through. Hole depth = wall thickness – 10 mm.
On average, 250 holes must be drilled for 20 meters of walls!
After drilling, dust remains in the hole, which reduces the depth by about 1/3. Our task is to
remove it from there. The hole must be clean to the full depth.
To do this, we use Air Compressor, Air Blow Gun + Vacuum cleaner.
When all the holes are cleared of dust, we proceed to the injection process. To do this, we use
a special low-pressure pump and a Damp Proof Course Cream.
The nose of the Air Gun is inserted to the end of the hole, pressure is applied and the nose is
slowly pulled back, filling the hole to the full depth with cream.
At the end of the injection, time is needed for the cream to be absorbed into the cement-sand
solution and into the brick. It usually takes 12-20 hours.
When the cream is absorbed, you can see a wet horizontal line along the entire treated wall.
This is the chemical DPC, a barrier that will not let moisture through itself up the wall.
Waterproofing Melbourne | Internal Wall Waterproofing | Damp Proofing | Rising Damp | Waterproofing Rising Damp
| Internal Waterproofing | Lateral Damp | Garage Waterproofing | AWC Group| Penetrating Damp | Crack Injection |
External Waterproofing | External Wall Waterproofing
I will not focus on how the cream works and why moisture cannot pass through it – this is
based on the chemical composition of the product and there is a detailed explanation on the
manufacturer’s website.
Depending on the situation, we either fill the holes with a special solution or leave the wall like
this. This is also negotiated before starting work.
And of course it is important to clean up after yourself. The work is quite dusty, a lot of
garbage in the form of removed render, removed rotten skirting boards.
We traditionally leave the site cleaner than it was before the start of work.