Module 4: Moisture Control & Damp Proofing 

 4.1 Causes of Damp in Buildings

Primary Sources of Moisture Ingress

• Construction Moisture: Water trapped in new builds (concrete, plaster)

• Ground Water: Capillary action through foundations (rising damp)

• Rain Penetration: Defective roofs, walls, or windows

• Plumbing Leaks: Burst pipes or faulty installations

• Condensation: High humidity + poor ventilation

• Human Activity: Cooking, bathing, drying clothes indoors

Contributing Factors

• Poor building maintenance

• Inadequate damp-proof courses

• Incorrect material selection

• Thermal bridging issues

• Climate conditions (high rainfall areas)

4.2 Types of Damp (Rising, Penetrating, Condensation)

A) Rising Damp

• Mechanism: Groundwater moves upward through porous materials

• Identification:

• Tide marks up to 1.2m high

• Salt deposits on walls

• Deteriorating skirting boards

• Affected Materials: Brick, stone, mortar

B) Penetrating Damp

• Causes:

• Roof leaks

• Cracked render

• Faulty gutters/downpipes

• Bridged cavities

• Characteristics:

• Localized damp patches

• Mold growth

• Damage follows water path

C) Condensation

• Process: Warm moist air condenses on cold surfaces

• Problem Areas:

• Cold bridges

• Poorly insulated areas

• Behind furniture on external walls

• Indicators:

• Black spot mold

• Window condensation

• Musty odors

Comparative Analysis

4.3 Damp-Proof Membranes (DPM) & Chemical DPCs

A) Damp-Proof Membranes (DPM)

• Materials:

• 1200-gauge polyethylene (standard)

• Bituminous sheets

• Liquid-applied coatings

• Installation Standards:

• Minimum 150mm overlaps

• Must lap with DPC in walls

• Sealed at penetrations

• Applications:

• Below ground floors

• Basement tanking

• Refurbishment projects

B) Chemical Damp-Proof Courses (DPC)

• Injection Methods:

• Cream injection (most common)

• Silane/siloxane-based

• Pressure injection for thick walls

• Installation Process:

• Drill at 120mm intervals

• Inject at low pressure

• Seal holes after treatment

• Effectiveness Factors:

• Wall thickness/porosity

• Injection depth

• Environmental conditions

DPC Selection Guide

4.4 Ventilation Strategies to Control Moisture

A) Passive Ventilation Systems

• Natural Ventilation:

• Trickle vents in windows

• Air bricks (minimum 1500mm² per m² floor)

• Chimney stack ventilation

• Stack Effect Utilization:

• Low-level inlets

• High-level outlets

• Minimum 1.5m vertical separation

B) Mechanical Ventilation

• Extract Fans:

• Intermittent (bathrooms/kitchens)

• Continuous (MEV systems)

• Whole-House Solutions:

• MVHR (Heat Recovery) - 85% efficiency

• PIV (Positive Input) systems

• Performance Standards:

• Minimum 8 l/s in wet rooms

• 4 air changes per day minimum

C) Hybrid Approaches

• Demand-Controlled Ventilation:

• Humidity sensors

• CO₂-activated systems

• Combined Solutions:

• Passive stack + boost fans

• MEV with humidity tracking

Integrated Moisture Management Plan

1. Diagnosis: Identify damp type (electronic meters, visual inspection)

2. Remediation: Address root cause (repairs, DPC installation)

3. Protection: Apply appropriate barriers (DPM, tanking)

4. Control: Implement ventilation strategy

5. Monitoring: Regular checks for recurrence

Common Mistakes in Damp Treatment

• Treating symptoms rather than causes

• Over-reliance on chemical DPCs without addressing drainage

• Blocking essential ventilation

• Using non-breathable materials on historic buildings

• Ignoring interstitial condensation risks

This module provides a systematic approach to diagnosing and treating damp problems while emphasizing the critical relationship between moisture control, building physics, and ventilation strategies. Proper application of these principles ensures healthy, durable buildings that meet modern performance standards.