Lateral Damp: Causes and Solutions for This Hidden Home Moisture Problem

Lateral Damp: Causes and Solutions for This Hidden Home Moisture Problem

While rising damp is a well-known issue in older properties, lateral damp is a lesser known but equally concerning source of excess moisture. Lateral damp refers to the horizontal transfer of moisture through walls, often going undetected for long periods. Left unchecked, it can lead to peeling paint, mold growth, rotting wood and other structural damage.

In this article, we’ll explore the common causes of lateral damp and what you can do to identify and rectify it – especially important when buying an older property in damp climates like Sydney.

What Causes Lateral Damp?

There are several potential causes of lateral damp in houses:

  • Leaking pipes: Faulty plumbing like cracks in drainage pipes inside walls allows water to seep horizontally into the surrounding materials. This often goes unnoticed until paint peels or leaks form.
  • Damaged roofing: Roof leaks above the horizontal damp course allow water to track laterally through brickwork rather than downwards. Flashing around chimneys is a common weak point.
  • Porous materials: Some old bricks and natural stone materials are more absorbent, allowing lateral moisture transfer even without an obvious moisture source.
  • Bridging the damp proof course: Garden beds, pathways or driveways that sit too high against the external walls can create moisture bridges that bypass the DPC.
  • Gutters and downpipes: Overflowing gutters or cracked downpipes release water that soaked into walls rather than down the pipes.

Identifying Lateral Damp

Lateral damp can be tricky to identify visually, but there are a few key signs to look for when inspecting a property:

  • Horizontal tide marks or staining on walls – especially under window sills internally.
  • Bubbling or flaking paint along the lower half of external walls.
  • Crumbling plaster around the edges of ceilings or cornices.
  • musty damp smells, particularly around fireplaces and chimneys.
  • Cracks or bulging in sections of brickwork that correspond to areas of saturation.
  • Efflorescence (white salty deposits) forming in patches rather than consistently.
  • Rotting skirting boards at the bottom of internal walls.

If you’re concerned about potential damp issues when buying a property, consider getting a professional pre-purchase building inspection. Inspectors have moisture meters that can detect excess moisture below the surface. This is the best way to identify lateral damp that may not have obvious visible signs.

Rectifying Lateral Damp

The specific treatment will depend on the underlying cause, but general solutions include:

  • Repair leaking pipes, gutters and roof damage to eliminate moisture sources. Applying waterproof sealants around chimneys, vents and roof flashing can help.
  • Improve drainage and runoff around the perimeter of the building and slope the ground away from foundations.
  • Lower external ground levels against walls to re-establish the damp proof course protection.
  • Apply an injected DPC cream into mortar beds 2-3 courses above ground to create a new chemical barrier (with council approvals).
  • Install a physical DPC – channels cut into mortar and filled with waterproof material – for more severe rising damp.
  • Apply polymer or bitumen tanking slurry coatings to form an impermeable layer on damp internal walls.
  • Remove lower sections of saturated plaster and brick and install new, more water-resistant materials. French drains underneath can also redirect moisture.
  • Ventilate affected areas to allow moisture to evaporate and prevent mold growth. Dehumidifiers can assist.

Prevention is ideal, and maintaining the exterior of the building – sealing cracks, cleaning gutters, appropriate landscaping etc. can help avoid lateral damp issues arising. But with early intervention and the right remedial work, existing lateral damp can be fully cured.

An experienced Sydney BuildingInspector Provides Expert Diagnosis

Lateral damp is best identified and diagnosed by a professional property inspector. At Inner West Property Inspections, our fully qualified inspectors use state-of-the-art moisture meters to detect even hidden damp issues. We can pinpoint the source and recommend tailored solutions.

Buying a property with unnoticed moisture problems could mean expensive rectification work down the track. Our comprehensive pre-purchase inspections provide complete peace of mind, so you know the true condition of the property before purchase. Contact Inner West Property Inspections today to book your Sydney pre-purchase inspection.

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