What is Wall Wrap (Sarking) and What Does It Do?

Wall wrap, also known as sarking, is a crucial component of the building envelope that often goes unnoticed but plays a vital role in protecting your home from moisture, improving energy efficiency, and enhancing overall building performance. Understanding what wall wrap is and how it works is essential for anyone involved in construction or home improvement.

This comprehensive guide will explain wall wrap (sarking), its functions, types, installation methods, and why it's essential for modern building construction.

What is Wall Wrap (Sarking)?

Definition and Purpose

Wall wrap (also called sarking, building wrap, or weather barrier) is a membrane material installed on the exterior side of wall framing, between the structural frame and the exterior cladding. It serves as a protective barrier that:

• Blocks moisture: Prevents water from entering the wall cavity
• Allows vapor diffusion: Allows water vapor to escape from the wall
• Improves energy efficiency: Reduces air infiltration and heat loss
• Protects insulation: Keeps insulation dry and effective

Historical Context

Traditional sarking:

• Original purpose: Originally used as a secondary weather barrier
• Materials: Traditionally made from felt, paper, or other materials
• Function: Basic moisture protection and wind resistance
• Evolution: Has evolved significantly with modern materials

Modern wall wrap:

• Advanced materials: Made from synthetic materials with advanced properties
• Multiple functions: Serves multiple functions beyond basic protection
• Performance standards: Must meet specific performance standards
• Building codes: Required by most modern building codes

Functions of Wall Wrap

Moisture Protection

Water resistance:

• Liquid water: Prevents liquid water from entering the wall cavity
• Wind-driven rain: Protects against wind-driven rain
• Capillary action: Prevents water from wicking through materials
• Condensation: Helps manage condensation within the wall

Vapor management:

• Vapor diffusion: Allows water vapor to diffuse through the material
• Moisture balance: Helps maintain proper moisture balance in the wall
• Drying potential: Allows walls to dry out when wet
• Humidity control: Helps control humidity levels in the building

Air Barrier Function

Air infiltration control:

• Air sealing: Reduces air infiltration through the wall
• Energy efficiency: Improves energy efficiency by reducing air leakage
• Comfort: Improves indoor comfort by reducing drafts
• HVAC efficiency: Improves HVAC system efficiency

Pressure equalization:

• Wind pressure: Helps equalize wind pressure across the wall
• Moisture management: Reduces moisture problems caused by pressure differences
• Structural protection: Protects structural elements from pressure damage
• Cladding protection: Protects cladding from pressure-related damage

Thermal Performance

Insulation protection:

• Moisture protection: Keeps insulation dry and effective
• Air movement: Reduces air movement through insulation
• Thermal bridging: Helps reduce thermal bridging
• Energy efficiency: Improves overall energy efficiency

Temperature management:

• Heat flow: Helps control heat flow through the wall
• Seasonal performance: Provides consistent performance year-round
• Comfort: Improves indoor comfort and temperature control
• Energy costs: Reduces energy costs for heating and cooling

Types of Wall Wrap

Traditional Materials

Felt paper:

• Material: Asphalt-impregnated felt paper
• Properties: Basic moisture resistance, limited durability
• Use: Still used in some applications
• Limitations: Limited performance and durability

Building paper:

• Material: Kraft paper with various treatments
• Properties: Better moisture resistance than felt
• Use: Common in residential construction
• Limitations: Limited durability and performance

Tar paper:

• Material: Asphalt-impregnated paper
• Properties: Good moisture resistance, limited durability
• Use: Traditional construction method
• Limitations: Limited performance and environmental concerns

Modern Synthetic Materials

Polyethylene (PE):

• Material: High-density polyethylene
• Properties: Excellent moisture resistance, good durability
• Use: Common in residential construction
• Benefits: Cost-effective, good performance

Polypropylene (PP):

• Material: Polypropylene with various treatments
• Properties: Good moisture resistance, excellent durability
• Use: Common in commercial construction
• Benefits: Good performance, reasonable cost

Polyolefin:

• Material: Various polyolefin materials
• Properties: Excellent moisture resistance, good durability
• Use: High-performance applications
• Benefits: Excellent performance, long-lasting

Specialty Materials

Breathable membranes:

• Material: Microporous materials
• Properties: Excellent vapor diffusion, good moisture resistance
• Use: High-performance applications
• Benefits: Excellent moisture management

Reflective materials:

• Material: Materials with reflective surfaces
• Properties: Good thermal performance, moisture resistance
• Use: Energy-efficient applications
• Benefits: Improved thermal performance

Self-adhesive materials:

• Material: Materials with adhesive backing
• Properties: Easy installation, good sealing
• Use: Difficult installation areas
• Benefits: Easy installation, good performance

Installation Methods

Preparation

Surface preparation:

• Clean surface: Ensure framing is clean and dry
• Inspect framing: Check for damage or defects
• Measure and cut: Measure and cut wall wrap to size
• Plan installation: Plan installation sequence and overlaps

Material handling:

• Storage: Store materials properly to prevent damage
• Handling: Handle materials carefully to prevent damage
• Cutting: Cut materials carefully to ensure proper fit
• Installation: Install materials according to manufacturer's instructions

Installation Process

Basic installation:

• Start at bottom: Begin installation at the bottom of the wall
• Overlap seams: Overlap seams according to manufacturer's instructions
• Secure edges: Secure edges with appropriate fasteners
• Work upward: Work upward, overlapping each course

Seam treatment:

• Overlap requirements: Follow manufacturer's overlap requirements
• Seam sealing: Seal seams with appropriate tape or adhesive
• Quality control: Ensure proper seam treatment
• Inspection: Inspect seams for proper installation

Penetration treatment:

• Window openings: Properly seal around window openings
• Door openings: Properly seal around door openings
• Utility penetrations: Properly seal around utility penetrations
• Quality control: Ensure proper penetration treatment

Quality Control

Installation inspection:

• Visual inspection: Visually inspect installation
• Seam inspection: Inspect seams for proper treatment
• Penetration inspection: Inspect penetrations for proper sealing
• Overall inspection: Inspect overall installation quality

Performance testing:

• Air leakage testing: Test for air leakage
• Moisture testing: Test for moisture problems
• Thermal testing: Test thermal performance
• Overall performance: Test overall performance

Building Code Requirements

Code Compliance

Building code requirements:

• Moisture protection: Must provide adequate moisture protection
• Air sealing: Must provide adequate air sealing
• Fire resistance: Must meet fire resistance requirements
• Durability: Must meet durability requirements

Performance standards:

• Water resistance: Must meet water resistance standards
• Vapor diffusion: Must meet vapor diffusion standards
• Air permeability: Must meet air permeability standards
• Durability: Must meet durability standards

Installation Requirements

Installation standards:

• Proper installation: Must be installed according to manufacturer's instructions
• Quality control: Must meet quality control requirements
• Inspection: Must pass inspection requirements
• Documentation: Must be properly documented

Professional requirements:

• Licensed installers: Must be installed by licensed professionals
• Quality assurance: Must meet quality assurance requirements
• Warranty: Must meet warranty requirements
• Compliance: Must meet compliance requirements

Common Problems and Solutions

Installation Problems

Common installation issues:

• Improper overlap: Seams not properly overlapped
• Poor sealing: Seams not properly sealed
• Inadequate fastening: Materials not properly fastened
• Poor penetration treatment: Penetrations not properly treated

Solutions:

• Proper training: Ensure installers are properly trained
• Quality control: Implement quality control procedures
• Regular inspection: Regular inspection during installation
• Professional installation: Use qualified professionals

Performance Problems

Common performance issues:

• Moisture problems: Moisture entering the wall cavity
• Air leakage: Excessive air leakage through the wall
• Thermal problems: Poor thermal performance
• Durability issues: Premature failure of materials

Solutions:

• Proper design: Ensure proper design and specification
• Quality materials: Use quality materials
• Proper installation: Ensure proper installation
• Regular maintenance: Regular maintenance and inspection

Maintenance and Inspection

Regular Inspection

Inspection frequency:

• Annual inspection: Annual inspection of wall wrap
• After events: Inspection after severe weather
• During renovations: Inspection during renovations
• Professional inspection: Professional inspection when needed

Inspection items:

• Material condition: Condition of wall wrap materials
• Seam condition: Condition of seams and seals
• Penetration condition: Condition of penetrations
• Overall performance: Overall performance of the system

Maintenance Requirements

Maintenance tasks:

• Seam maintenance: Maintaining seams and seals
• Penetration maintenance: Maintaining penetrations
• Material maintenance: Maintaining wall wrap materials
• Overall maintenance: Overall system maintenance

Maintenance procedures:

• Regular cleaning: Regular cleaning of wall wrap
• Seam repair: Repairing damaged seams
• Penetration repair: Repairing damaged penetrations
• Material replacement: Replacing damaged materials

The Bottom Line

Wall wrap (sarking) is a critical component of the building envelope that provides essential protection against moisture, improves energy efficiency, and enhances overall building performance. Understanding its functions and proper installation is essential for ensuring long-term building performance.

Remember: Wall wrap is an investment in the long-term performance of your building. Proper selection, installation, and maintenance will ensure your building performs well and remains protected from moisture and other environmental factors.

The key to successful wall wrap installation is:

• Choose the right material for your specific application
• Follow manufacturer's instructions for proper installation
• Ensure proper sealing of seams and penetrations
• Use qualified professionals for installation and maintenance
• Regular inspection and maintenance to ensure ongoing performance

Start with a clear understanding of your building's requirements, then work with qualified professionals to select and install the wall wrap system that's right for your specific needs.

Ready to continue building your home? Learn about A Guide to Insulation: Batts, Foam, and Reflective and discover Where to Insulate in Your Home for Maximum Efficiency to complete your building envelope knowledge.