Master Flash® Roof Flashing for Chimney and Flue Pipes

Create a secure, weather-resistant seal where a chimney, stove flue or ventilation pipe passes through the roof with a genuine Master Flash® roof flashing.

Designed with a flexible rubber boot and mouldable base, Master Flash® adapts closely around the pipe and follows the shape of the roof covering. This helps prevent rainwater from entering around the penetration while producing a clean, professional finish.

Ideal for stove installers, heating engineers, roofers and competent DIY users, it provides a dependable alternative to fabricating a flashing from separate materials on site.

Ideal for External Stove Flues

Master Flash® is particularly useful when installing an external chimney system through:

• Metal roofing
• Profiled and corrugated sheets
• Garage and workshop roofs
• Garden room roofs
• Outbuildings
• Commercial and agricultural roof sheets
• Suitable flat or pitched roof systems

It can be used around compatible:

• Twin-wall insulated chimney systems
• Stove flue pipes
• Ventilation pipes
• Extractor and exhaust ducts
• Plumbing and service penetrations

Flexible, Secure Fit

The stepped rubber cone can be trimmed to suit the required pipe diameter. Once cut, it stretches around the pipe to form a close-fitting seal.

Its flexible base can then be carefully shaped to match the roof profile, making it especially effective on corrugated and profiled metal roofing.

For best results, the base should be installed with the appropriate weatherproof sealant and suitable fixings.

EPDM or High-Temperature Silicone

Master Flash® roof flashings are available in different materials to suit different applications.

EPDM Master Flash®

EPDM provides excellent flexibility and resistance to normal outdoor weathering. It is commonly selected for ventilation pipes and installations where the flashing will remain within its specified operating temperature.

Silicone Master Flash®

Silicone models are designed for applications involving higher surface temperatures. They may be more appropriate around certain chimney and flue systems, subject to the flashing’s stated temperature rating and the chimney manufacturer’s installation requirements.

Always check the expected external pipe temperature before selecting the material. The flashing must not be used where the temperature or required combustible clearance exceeds its approved specification.

Why Choose Master Flash®?

• Creates a weather-resistant seal around roof penetrations
• Flexible cone accommodates a range of pipe diameters
• Mouldable base follows profiled and corrugated roofing
• Suitable for flat and pitched installations, depending on the model
• Resistant to outdoor weathering, UV exposure and ozone
• Faster and neater than fabricating a flashing on site
• Available in multiple sizes for different flue diameters
• EPDM and higher-temperature silicone options available

Choosing the Correct Size

Each Master Flash® model covers a specific range of pipe diameters.

Before ordering:

1. Measure the outside diameter of the pipe, not its internal flue size.
2. Check that the measured diameter sits within the selected flashing’s cutting range.
3. Confirm whether EPDM or silicone is appropriate for the expected temperature.
4. Check that the base dimensions are suitable for the roof profile and available fixing area.

Twin-wall chimney systems have a larger outside diameter than their internal flue measurement. For example, a chimney described as a 5″ system will normally require a flashing selected using the full external diameter of the twin-wall pipe.

Installation Guidance

The cone should be cut carefully at the correct marked diameter, generally slightly smaller than the pipe to create a close seal. The base is then shaped to the roof and secured using suitable sealant and corrosion-resistant fixings.

Do not rely on sealant alone. The flashing should be mechanically fixed in accordance with the roof and flashing manufacturer’s instructions.

A storm collar may also be required above the flashing to divert rainwater away from the pipe opening and improve weather protection.

Important Information

Master Flash® seals the roof penetration but does not replace the chimney manufacturer’s support components, fire-stop plates, ventilation requirements or combustible clearances.

For solid-fuel and wood-burning stove installations, always follow:

• The appliance manufacturer’s instructions
• The chimney system manufacturer’s instructions
• Current Building Regulations
• The flashing’s approved temperature limits
• Required distances from combustible materials

Installation by a suitably competent person is strongly recommended.