What is Rising Damp?
Rising damp occurs when groundwater travels upwards through porous building materials like brick, stone, or mortar. This happens through a process called capillary action – the same way water travels up through a plant stem.
In a properly constructed building, a damp proof course (DPC) prevents this moisture from rising. However, when the DPC fails, is bridged, or is absent altogether, rising damp can become a serious problem.
How to Identify Rising Damp
Visual Signs
Look for these telltale indicators:
- Tide marks – A visible line of staining or salt deposits, typically up to 1 metre from floor level
- Salt deposits – White, fluffy crystite deposits (efflorescence) on walls
- Peeling wallpaper – Paper lifting away from walls, especially at the bottom
- Bubbling or flaking paint – Paint failing due to moisture beneath
- Damaged skirting boards – Warped, rotting, or lifting skirting
- Musty smell – A damp, earthy odour in affected rooms
The Height Test
Rising damp rarely exceeds 1.2 metres (about 4 feet) in height. If damp patches extend higher than this, you may be dealing with penetrating damp or condensation instead.
Moisture Patterns
Rising damp typically:
- Affects ground floor walls only
- Is worse in winter when groundwater levels are higher
- Appears on internal and external walls
- Creates a relatively even dampness across affected areas
What Causes Rising Damp?
Failed DPC
The most common cause. DPCs can fail due to:
- Age and deterioration
- Poor original installation
- Physical damage
Bridged DPC
The DPC can be bypassed when:
- External ground levels are raised above the DPC
- Internal floors are raised
- Render or pebbledash covers the DPC
- Debris accumulates against external walls
No DPC Present
Many older properties (pre-1875) were built without a DPC. These buildings rely on natural evaporation, which can be compromised by:
- Modern impermeable finishes
- Blocked ventilation
- Cement pointing replacing lime mortar
Rising Damp vs Other Damp Types
Rising Damp Checklist:
✓ Affects ground floor walls only ✓ Visible tide marks below 1.2m ✓ Salt deposits present ✓ Worse in winter months ✓ Both internal and external walls affected
Condensation Indicators:
✗ Black mould growth ✗ Water droplets on windows ✗ Worse in bathrooms and kitchens ✗ Improves with ventilation
Penetrating Damp Indicators:
✗ Appears after rainfall ✗ Can occur at any height ✗ Often around windows or chimneys ✗ Usually external walls only
What to Do If You Have Rising Damp
Step 1: Get a Professional Survey
A qualified damp surveyor will:
- Use calibrated moisture metres
- Check for salt contamination
- Inspect existing DPC
- Identify the root cause
- Provide a detailed report and quotation
Step 2: Address the Cause
This may involve:
- Installing a new chemical DPC
- Lowering external ground levels
- Removing render bridging the DPC
- Improving sub-floor ventilation
Step 3: Remedial Works
After treating the cause:
- Remove contaminated plaster
- Apply renovation plaster with salt-inhibiting properties
- Allow adequate drying time
- Redecorate with breathable paints
Step 4: Prevention
Maintain your property by:
- Keeping external ground levels low
- Ensuring adequate ventilation
- Using breathable finishes
- Regular inspection of DPC areas
The Cost of Ignoring Rising Damp
If left untreated, rising damp can cause:
- Structural timber decay (wet rot)
- Plaster and decoration damage
- Damaged floor coverings
- Reduced property value
- Health issues from mould growth
- Higher heating costs
Getting Help
If you’ve noticed any signs of rising damp in your property, early intervention is crucial. Our free damp surveys provide a comprehensive assessment and clear treatment recommendations.
Book your free survey today or call our team for expert advice.