Roofshield Air and Vapour Permeable Breathable Membrane – 1m x 50m

Roofshield Air and Vapour Permeable Breathable Membrane is a high-performance pitched roofing underlay manufactured by Don & Low and designed to provide exceptional air and vapour permeability while protecting the roof structure against rain, wind and snow.

First launched in 1996, Roofshield has been used within the roofing industry for more than 25 years. Its distinctive three-layer construction with a patented Meltblown core allows both moisture vapour and air to pass through the membrane, helping manage moisture and significantly reduce the risk of interstitial condensation within pitched roof constructions.

Unlike conventional airtight breathable membranes, Roofshield combines extremely low vapour resistance with controlled air permeability. In appropriate non-ventilated cold pitched roof constructions, its BBA-certified performance can eliminate the requirement for conventional roof-space ventilation and, where covered by the certified construction, a separate vapour control layer.

Roofshield is BBA certified for use in non-ventilated cold and warm pitched roofs, including fully supported and unsupported applications.

Each green 1m x 50m roll provides 50m² of nominal coverage and weighs 185gsm.

What is Roofshield Breathable Membrane Used For?

Roofshield is designed primarily as an air and vapour permeable roofing underlay for pitched roof constructions.

Typical applications include:

• Cold pitched roofs
• Warm pitched roofs
• Non-ventilated cold roofs
• Non-ventilated warm roofs
• Fully supported roofing applications
• Unsupported roofing applications
• New-build pitched roofs
• Extensions
• Loft conversions
• Roof refurbishments
• Renovation projects
• Timber pitched roof structures

Its unusual combination of air permeability, very low vapour resistance and water resistance makes Roofshield particularly useful in roof constructions where effective moisture management is required.

Air and Vapour Permeable Roofing Underlay

Roofshield differs from many conventional breathable roofing membranes because it is both air permeable and highly vapour permeable.

Its patented Meltblown core allows moisture vapour to diffuse through the membrane while also facilitating controlled air movement.

This combination helps moisture escape from the roof structure and can provide effective condensation management without relying solely on traditional roof-space ventilation.

Exceptionally Low Vapour Resistance

Roofshield has a stated vapour resistance of just 0.065 MNs/g and an Sd-value of 0.013m.

These figures demonstrate the membrane’s very high level of vapour permeability.

The extremely low resistance allows moisture vapour to migrate through Roofshield readily, helping prevent moisture from becoming trapped within the roof construction.

This is particularly beneficial during periods of elevated internal humidity and while new buildings are drying out.

Patented Meltblown Core

At the centre of Roofshield’s performance is its patented Meltblown core.

The three-layer membrane construction is engineered to provide the combination of physical properties required from a high-performance pitched roofing underlay, including:

• Air permeability
• Very high vapour permeability
• Water resistance
• Strength
• Flexibility
• Weather protection

This construction has remained central to Roofshield since its introduction in 1996.

Helps Reduce Interstitial Condensation

Interstitial condensation occurs when moisture vapour enters a building element and condenses on colder surfaces within the construction.

Roofshield helps manage this risk by allowing both air and moisture vapour to pass through the roofing underlay.

Moisture can therefore diffuse outward rather than becoming trapped within the roof space or roof build-up.

This can help protect:

• Roof insulation
• Timber rafters
• Roof decking
• Battens
• Structural components
• Other moisture-sensitive materials

The complete roof should still be designed and installed according to the applicable requirements for the particular construction.

Air Permeability of 34.4m³/m²·h at 50Pa

Roofshield has a certified air permeability of 34.4m³/m²·h at 50Pa.

This controlled air permeability allows air movement through the membrane itself, distinguishing Roofshield from conventional airtight low-resistance roofing underlays.

The combination of air movement and vapour diffusion helps Roofshield deal effectively with moisture within appropriate pitched roof constructions.

Uniform Airflow Through the Roof

Roofshield’s air-permeable construction helps create more uniform air movement across the roof area.

Rather than relying entirely on discrete ventilation openings at particular locations, the membrane itself allows controlled air movement across its surface.

According to the manufacturer’s certified system design, this can provide effective moisture management within non-ventilated pitched roof constructions without the elaborate ventilation hardware associated with conventional roof-space ventilation strategies.

No Roof-Space Ventilation in Certified Cold Roof Applications

One of the principal advantages of Roofshield is its ability to be used in appropriate non-ventilated cold pitched roof constructions.

Roofshield is BBA certified for these applications, allowing moisture to diffuse through the roofing underlay rather than relying on conventional roof-space ventilation.

Where the complete construction falls within the scope of the relevant certification and installation requirements, this can eliminate components such as:

• Eaves ventilation
• Ridge ventilation
• High-level ventilation
• Other conventional roof-space ventilation hardware

This can simplify roof construction and potentially reduce both installation time and material costs.

No Separate VCL Required in Certified Cold Roof Constructions

Roofshield also offers an unusual advantage within appropriate non-ventilated cold pitched roof constructions.

The BBA certification for the relevant Roofshield construction states that a separate vapour control layer (VCL) is not required.

This can simplify the overall roof build-up and reduce the number of separate membrane layers required.

This provision relates specifically to roof constructions falling within the scope of the Roofshield certification. A VCL should not be omitted from other constructions simply because Roofshield is being used. The complete roof specification and applicable certification should always be followed.

Secondary Weather Protection

Roofshield provides a reliable secondary barrier beneath the primary roof covering.

It helps protect the roof structure against:

• Wind-driven rain
• Snow
• Wind
• Dust
• Moisture penetrating beneath tiles or slates

Roof tiles, slates or other discontinuous roofing materials remain the primary weatherproof covering, while Roofshield provides additional protection beneath.

W1 Resistance to Water Penetration

Roofshield achieves a W1 classification for resistance to water penetration under EN 13859-1.

The manufacturer states that the membrane can withstand a water column exceeding one metre without leakage.

This high level of water resistance allows Roofshield to provide effective secondary weather protection beneath the finished roof covering while remaining highly permeable to air and water vapour.

Up to 3 Months Temporary Exposure

Roofshield can provide temporary weather protection for up to three months when exposed, according to the manufacturer’s stated performance.

This can provide useful protection to the building envelope during construction while the permanent roof covering is being completed.

The product should still be installed, exposed and subsequently covered in accordance with the manufacturer’s requirements.

Suitable for Non-Ventilated Cold Pitched Roofs

Roofshield is particularly well known for its use in non-ventilated cold pitched roof systems.

The air and vapour permeability of the membrane allows moisture to escape through the underlay, providing an alternative approach to conventional roof-space ventilation.

Roofshield was the first membrane certified for use in cold non-ventilated pitched roofs and has held certification for this application since 1996.

Suitable for Non-Ventilated Warm Pitched Roofs

Roofshield is also BBA certified for appropriate non-ventilated warm pitched roof constructions.

This provides flexibility when specifying the membrane across different pitched roof insulation strategies.

The complete roof build-up should be designed according to the specific thermal and moisture-control requirements of the project.

Fully Supported Roofing Applications

Roofshield can be used within appropriate fully supported pitched roof constructions.

This can include applications where the membrane is installed over suitable roof decking or other continuous supporting surfaces.

The specific installation method should follow the manufacturer’s requirements and relevant certification.

Unsupported Roofing Applications

Roofshield is also certified for appropriate unsupported pitched roofing applications.

This allows the membrane to be installed across a broad range of traditional and modern roof constructions.

NHBC Accepted

Roofshield is accepted for appropriate NHBC applications.

With its certified air permeability of 34.4m³/m²·h at 50Pa, Roofshield can eliminate the requirement for additional high-level ventilation on relevant NHBC-approved roof constructions.

This allows the same Roofshield specification to be used across a broad range of appropriate housing projects while simplifying roof ventilation detailing.

BBA Certified Since 1996

Roofshield has been BBA certified for appropriate non-ventilated warm and cold pitched roof applications since 1996.

The certification provides independent assessment of Roofshield for its intended roofing applications and confirms the suitability of the membrane within the specified constructions.

Its long certification history has helped establish Roofshield as a widely recognised air and vapour permeable roofing underlay.

BS 5534 Compliance

Roofshield is independently tested and specified as BS 5534 compliant for appropriate pitched roofing applications across the UK.

BS 5534 covers slating and tiling for pitched roofs and associated fixing requirements.

The complete roofing system should still be designed according to project-specific factors such as roof pitch, exposure, roof covering, batten arrangement and fixing requirements.

Made in the UK by Don & Low

Roofshield was developed by Don & Low and launched in 1996.

The membrane continues to be manufactured by Don & Low in the UK, providing a long-established roofing underlay specification with more than 25 years of continuous use and testing.

Durable 185gsm Construction

Roofshield has a stated weight of 185gsm, providing a substantial membrane construction for roofing applications.

The combination of its three-layer structure and patented Meltblown core provides the physical properties required for:

• Roofing installation
• Weather resistance
• Moisture management
• Air permeability
• Vapour permeability
• Long-term use within the roof construction

50m² Nominal Coverage

Each Roofshield roll measures:

1m wide x 50m long

providing:

50m² nominal coverage per roll

Actual installed coverage will be lower once the required membrane laps are taken into account.

When calculating quantities, allowance should be made for:

• Horizontal overlaps
• Vertical overlaps
• Hips
• Valleys
• Openings and penetrations
• Cutting
• Detailing
• Site wastage

Green Roofing Membrane

Roofshield is supplied in its distinctive green finish, making it easily identifiable on site and distinguishing it from other roofing membranes within the Don & Low range.

Key Features and Benefits

• Air and vapour permeable membrane: Allows both controlled air movement and moisture vapour diffusion
• Extremely low vapour resistance: Just 0.065 MNs/g
• Low Sd-value: 0.013m
• Certified air permeability: 34.4m³/m²·h at 50Pa
• Patented Meltblown core: Specialist three-layer membrane construction
• Helps reduce condensation risk: Allows moisture to escape from the roof structure
• Uniform airflow: Air permeability helps distribute air movement across the roof
• W1 water resistance: Excellent resistance to water penetration
• Secondary weather barrier: Helps protect against rain, wind and snow
• Up to three months temporary exposure: Manufacturer-stated temporary weather protection
• Non-ventilated cold roofs: BBA certified for appropriate cold roof constructions
• Non-ventilated warm roofs: BBA certified for appropriate warm roof constructions
• No conventional roof-space ventilation: Not required in appropriate certified cold roof constructions
• No separate VCL: Not required in applicable BBA-certified non-ventilated cold pitched roof constructions
• Fully supported applications: Suitable for appropriate supported roof systems
• Unsupported applications: Suitable for appropriate unsupported roof systems
• BBA certified: Independently assessed for relevant roofing applications
• NHBC accepted: Suitable for appropriate NHBC-approved applications
• BS 5534 compliant: Independently tested for pitched roofing applications
• EN 13859-1: W1 water resistance classification
• 185gsm construction: Substantial and durable roofing membrane
• 50m² roll: 1m x 50m nominal coverage
• Made in the UK: Manufactured by Don & Low
• Established since 1996: More than 25 years of continuous use and development

Roofshield Air and Vapour Permeable Breathable Membrane Specification

Why Choose Roofshield Air and Vapour Permeable Breathable Membrane?

Roofshield Air and Vapour Permeable Breathable Membrane provides a distinctive approach to pitched roof moisture management by combining extremely high vapour permeability with controlled air permeability.

With a vapour resistance of only 0.065 MNs/g, an Sd-value of 0.013m and certified air permeability of 34.4m³/m²·h at 50Pa, Roofshield allows moisture and air movement through the underlay while maintaining W1 resistance to water penetration.

Its patented three-layer Meltblown construction helps reduce the risk of interstitial condensation and enables Roofshield to be used within BBA-certified non-ventilated warm and cold pitched roof systems, including fully supported and unsupported applications.

In appropriate certified non-ventilated cold roof constructions, Roofshield can remove the requirement for conventional roof-space ventilation and a separate vapour control layer, simplifying installation and potentially reducing labour and material requirements.

Made in the UK by Don & Low and continuously used since its launch in 1996, Roofshield is a proven choice for projects requiring a high-performance breathable roofing membrane, air-permeable roof underlay or vapour-permeable membrane for non-ventilated pitched roofs.

Each 1m x 50m roll provides 50m² of nominal coverage and has a robust 185gsm construction.