What is Roof Flashing?

Roof flashing is a vital component of any roofing system. It refers to thin pieces of impervious material, typically sheet metal such as steel or aluminium, strategically installed at certain points on a roof to create a weather-resistant envelope. These points often include areas where the roof meets a vertical structure, such as chimneys, skylights, vents, and door and window frames, which are naturally susceptible to water ingress.

The importance of roof flashing cannot be overstated. It plays a pivotal role in maintaining the integrity of a building by preventing water from entering the structure. Without proper flashing, these areas become entry points for moisture, leading to serious problems such as rot, mould, and structural damage.

Roof flashing serves as a barrier against water leakage. It is designed to divert water away from potential infiltration points, thereby ensuring the roof remains waterproof. It also provides weather resistance to wall cladding and prevents gutters from over-filling, which can cause damage and encourage the growth of toxic moulds.

Asphalt shingles are a common roofing material that often requires the use of flashing. The flashing is typically installed around the edges and joints of the shingles to prevent water from seeping underneath. For asphalt shingle roofs, the commonly used flashing types are made of galvanized steel or aluminum.

Metal roofs, due to their design and material, are susceptible to expansion and contraction. Therefore, flashing is essential to accommodate these movements and prevent water ingress. The flashing for metal roofs is often made from galvanised steel or aluminium to resist corrosion.

Tile roofs, particularly those with complex designs or multiple intersections, require flashing to ensure all gaps and joints are adequately sealed against water penetration. For tile roofs, the commonly used types of roof flashing are typically made of lead, copper, or galvanized steel. The choice among these materials depends on factors like the specific design of the roof, the local climate, and budget.

Rubber roofs, also known as EPDM roofs, often utilise rubberised flashing. This type of flashing is flexible and can easily conform to the roof’s contours, providing an effective seal against water.

The interaction between roofing materials and roof flashing is crucial in maintaining a waterproof roofing system. The flashing must be compatible with the roofing material to ensure a seamless and effective seal. For instance, metal flashing is commonly used with asphalt shingles, while rubberised flashing is often paired with rubber roofs.

Lopez-Arce, P., Altamirano-Medina, H., Berry, J. et al. Building moisture diagnosis: Processing, assessing and representation of environmental data for root cause analysis of mould growth. Build. Simul. 13, 999–1008 (2020) https://doi.org/10.1007/s12273-020-0680-8, “The occurrence of surface condensation and mould can lead to concerns of poor indoor air quality and adverse health implications of occupants”. Pleasingly, the prevention of water leakage is one of the primary functions of roof flashing. By diverting water away from potential infiltration points, flashing plays a vital role in maintaining the structural integrity of a building and preventing issues such as damp, mould, and rot.

Roof flashing contributes significantly to the waterproofing and moisture protection of a building. It forms a barrier that prevents water from entering the structure, thereby protecting the interior from moisture-related damage.

Roof drainage systems, such as gutters and downspouts, work hand in hand with roof flashing. The flashing directs water towards the gutters, which then channel the water away from the building. This combined action ensures the effective removal of water from the roof, reducing the risk of water ingress and associated damage.

In roofing construction and repair, flashing is used to seal and protect the various joints and intersections ona roof. It is often customised to suit the specific requirements of the roof, ensuring a tight seal and effective waterproofing. During roof flashing repairs, existing flashing may need to be replaced or new flashing installed to address any areas of concern.

The installation of roof flashing involves several techniques and methods. It can be installed like shingles, with one piece overlapping another, or sealed to function as one continuous surface. The flashing is typically fastened using nails or screws, and sealant may be applied to ensure a watertight seal.

Roof flashing installation, repair, and maintenance should always be carried out by qualified professionals. They have the knowledge and expertise to ensure the flashing is correctly installed and maintained, thereby maximising its effectiveness and lifespan. Regular inspections and maintenance are crucial to identify and address any issues promptly.

There are numerous types of roof flashing, each designed to suit specific applications and roof styles. These include:

1. Chimney Flashing: Used around chimneys to prevent water ingress. It is often made from copper due to its durability and resistance to corrosion.
2. Vent Pipe Flashing: Designed to waterproof pipes and other roof protrusions. It is typically made from galvanised steel or aluminium.
3. Valley Flashing: Installed in the valleys of a roof where two slopes meet. It is often made from sheet metal to withstand the high volume of water flow.
4. Step Flashing: Comprises overlapping pieces that create a waterproof barrier on sloped roofs. It is typically made from galvanised steel or aluminium.
5. Wall Flashing: Found near windows and points of structural support to prevent water entry. It is often made from copper or steel.
6. Cap Flashing: A concealed flashing used above doors and windows. It is typically made from aluminium or steel.
7. Sill Flashing: Placed under doors or windows to prevent water ingress. It is often made from aluminium or steel.
8. Through-wall Flashing: Spans the thickness of a wall and directs water to drainage holes. It is typically made from copper or galvanised steel.
9. Kickout Flashing: Used at the bottom of a wall or roof intersection to deflect water away. It is often made from galvanised steel or aluminium.
10. Roof Penetration Flashing: Waterproofs pipes, supports, and other roof protrusions. It is typically made from galvanised steel or aluminium.
11. Channel Flashing: Shaped like a “U” to catch water where the edge of a roof meets a wall. It is often made from galvanised steel or aluminium.
12. Apron Flashing: Diverts water from a vertical surface into a gutter or covers the joint between a vertical surface and a sloping roof. It is often made from galvanised steel or aluminium.
13. Roll-top Ridge Flashing: Covers the ridge where two roof surfaces meet. It is typically made from galvanised steel or aluminium.
14. Box Guttering Flashing: A square or rectangular gutter used within the boundaries of the roof. It is often made from galvanised steel or aluminium.
15. Fascia Flashing: Connected to fascias, adding a decorative finish to a roof’s edge. It is often made from copper or steel.

Roof flashing covers a wide range of components and areas on a roof. It is typically installed around any feature that interrupts the roof’s surface, such as chimneys, vents, and skylights, as well as at intersections and terminations of surfaces and roofing systems. It is also used around windows and doors, and in areas where the roof meets a wall.

Roofing materials, construction, and roof flashing are governed by various regulations to ensure safety and quality. In Australia, these guidelines are contained in the Installation Code for Metal Roof and Wall Cladding (HB39-1997). This code provides comprehensive instructions on the design, fastening and correct cutting of flashing, among other things. SA HB 39 Metal roof and wall cladding installation, is considered to be a companion document to AS 1562.1 Design and installation of Sheet Roof and Wall Cladding.

Compliance with roofing codes and permits is crucial in any construction or renovation project. These codes ensure that the roofing materials, including flashing, are installed correctly and safely. They also ensure that the materials used are compatible and suitable for the specific environmental conditions of the location.

Roof flashing can have a significant impact on a building’s energy efficiency and insulation. By preventing water ingress and air leaks, flashing helps maintain the building’s internal temperature, reducing the need for heating and cooling and thereby increasing energy efficiency.

Energy-efficient roofing systems often incorporate high-quality roof flashing. This is because effective flashing contributes to the overall insulation of the building, preventing heat loss in winter and heat gain in summer. Therefore, when choosing insulation materials, it’s important to consider their compatibility with the flashing to ensure maximum energy efficiency.

Proper insulation with roof flashing can be achieved through several techniques. These include ensuring a tight seal at all joints and intersections, using compatible materials for the flashing and the rest of the roof, and regular maintenance to ensure the flashing remains in good condition. By following these techniques, roof flashing can contribute significantly to a building’s overall insulation and energy efficiency.

Several factors influence the lifespan of roof flashing. These include the material used, the quality of installation, the local climate, and the level of maintenance. For instance, metal flashing, such as copper or stainless steel, tends to have a longer lifespan than rubber or acrylic flashing. Similarly, flashing that is correctly installed and regularly maintained is likely to last longer.

The durability of roof flashing varies depending on the type. Metal flashing, particularly those made from copper or stainless steel, is highly durable and resistant to weathering. On the other hand, rubber or acrylic flashing, while flexible and easy to install, may not be as durable in the long term, particularly in harsh climates.

Regular maintenance is crucial to extend the lifespan of roof flashing. This includes regular inspections to identify any signs of damage or wear, such as rust, cracks, or loosening. If damage is detected, the flashing should be repaired or replaced immediately to prevent water ingress.

Roof flashing is a critical component of any roofing system, providing essential protection against water ingress and contributing to the building’s energy efficiency, aesthetic appeal, and sustainability. By understanding the different types of flashing and their various roles, you can make informed decisions when constructing or renovating your building. Furthermore, the use of durable materials such as steel, aluminium, and copper for roof flashing not only ensures longevity but also withstands harsh weather conditions, including strong winds and corrosion. Galvanised flashing, in particular, offers an extra layer of protection against rust, making it an excellent choice for long-term durability. With the right materials and proper installation, roof flashing can safeguard your home while enhancing its aesthetic appeal and energy efficiency.