What Does Rising Damp Really Cost to Fix? (2026 Australian Guide)
Rising damp is flagged in roughly 1 in 4 Australian building inspection reports. But the term covers a wide range of severity - from minor cosmetic staining to serious structural moisture damage.
## What Is Rising Damp?
Rising damp occurs when groundwater is drawn up through masonry walls by capillary action. The moisture carries salts from the ground, which are deposited on wall surfaces as the water evaporates (visible as white crystalline deposits called "efflorescence").
## How Much Does Treatment Cost?
**Chemical injection damp course:** $80–$120 per linear metre. For a typical 3-bedroom house (roughly 60m perimeter), that's $4,800–$7,200.
**Sub-floor ventilation:** $2,500–$6,000 for a mechanical ventilation system. This addresses the underlying moisture problem.
**Replastering affected walls:** $50–$80 per square metre. Salt-affected plaster must be removed and replaced with a salt-resistant render.
**Total realistic cost for a moderate case:** $6,000–$15,000.
## What Happens If You Ignore It?
Untreated rising damp progressively damages:
- **Internal plaster and paint** - peeling, bubbling, staining
- **Timber skirtings and framing** - rot, requiring replacement
- **Structural mortar joints** - erosion and weakening of brickwork
- **Indoor air quality** - mould growth from chronic moisture
A $5,000 problem today becomes a $15,000–$25,000 problem in 5 years.
## Negotiating With the Seller
If your building inspection flags rising damp:
1. Get a specialist damp report ($300–$600) for an accurate scope and quote
2. Use the cost estimate to negotiate the purchase price down
3. Ask the seller if rising damp has been previously treated - retreatment may be needed if an old damp course has failed
## Key Questions to Ask
- "Has this property had any previous damp treatment?"
- "When was the sub-floor last inspected?"
- "Are there any warranties on existing damp-proofing?"
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