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Rising damp: The scourge of old homes - featured image
By Leanne Spring

Rising damp: The scourge of old homes

You’ve found the ideal new home – a beautiful established terrace and then comes the shock.

The building and pest inspection reveal rising damp.

Rising damp is when moisture from under the house gets into the internal walls.

Person Showing The Wall Covered With Lichen

So what should you do?

You’ll often be able to tell a home has rising damp when you enter, because there’s a tell-tale sign of a musty odour.

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Note: Fact is, a high proportion of older buildings are affected by rising damp to some degree or another.

Unfortunately, some newer buildings also suffer from rising damp as they were not constructed properly.

Although rising damp can affect any brick house, older homes with poor underfloor ventilation in Sydney and Melbourne are most at risk.

Rising dampness occurs when moisture from the soil surrounding the home finds a way into the structure of your home creating damp conditions that allows mould to thrive.

The moisture can also draw up salt from the ground, which crystallises in the bricks and causes plaster to flake and paint to blister.

Known as efflorescence, in severe cases, it can even erode the masonry and cause significant damage if left unchecked.

Now there's nothing new about this - rising damp is an issue that has troubled homeowners since Roman times.

What causes rising damp?

Most houses are built with a damp-proof course between the foundations and the walls to prevent moisture absorption, but in older houses, these are often damaged and in some cases were never installed in the first place.

This allows groundwater to rise up through the bricks and mortar of a building by a process known as "capillary action."

It’s a bit like the way that oil rises up through the wick of a lamp.

How high the water rises depends on several factors including the efficiency of any original damp-proof course, the volume of the water supply, evaporative conditions over the wall surface and humidity.

What does it do to the building?

Rising damp can cause a number of aesthetic, structural, and even health-related problems.

  1. Aesthetically, rising damp can cause a musty smell as well as peeling, cracking, and bubbling of paint or plasterwork and create water-tide marks that show where the water has risen to along walls.

    It can also leave a white salt deposit (efflorescence ) which also looks unsightly on walls, floors or ceilings.
  2. Structurally, damp can get into timber structures and skirting boards causing them to rot.
    Also when the water rises it can deposit salt in building structures which causes corrosion and deterioration of integrity through a phenomenon known as salt attack.
    The problem is that superficial treatments such as repainting, coating, or cleaning the surface won't make it go away.
    Of course, evidence of rising damp may scare off potential buyers or tenants thereby devaluing your property.
  3. Health - Mildew, mould, and other microorganisms that thrive in wet and damp environments can be harmful to the occupants' health.
    The damp itself can aggravate conditions such as asthma and allergies.

If rising damp is left untreated, it can expose the owners of the property to legal action.

Certain federal and local building regulations require regular checkups and inspections to make sure that buildings are safe and secure locations to work and live in.

Non-compliance may result in a hefty fine and other legal issues.

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What’s the treatment?

Unwanted moisture in a house can spell a lot of problems.

While a little damp spot here and there is fine, if it stays longer and gets bigger, then it might be a cause for concern.

Treatment of rising damp is known as "damp-proofing" or "damp coursing" and typically involves stripping any plaster that’s damp off the wall, then drilling a line of holes along the wall at base level and injecting a silicone solution into the wall which penetrates to create a permanent barrier in the wall.

Then the walls are replastered using a salt retardant render.

How much does it cost to repair?

It is difficult to get a "ballpark" quote for damp proofing, as it is notoriously tricky to diagnose the source or scale of damp-related problems.

Every job is different and has to be assessed by a damp proofing professional, but a rule of thumb is to budget about $300 per metre

This means a terrace house with significant rising damp issues could cost up to $10,000 to repair, but the cost could be triple this in a severe case.

About Leanne Spring Leanne is a highly experienced Buyers Agent in the Brisbane Real Estate market. Leanne became a passionate lover of property in 2001. Since then, both professionally and personally, she has been involved in all aspects of property including purchasing, negotiating, renovating, and selling.
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