Roof Flashings & Cappings

About Roof Flashings and Cappings 

Proper waterproofing plays a critical role in the protection of the building. Without good rainwater management, roof, walls, and gradually the entire structure will be exposed to quick deterioration. 

Roof flashings and cappings are the last elements of roof installation. They are placed at the end of the shingle and bent to overlap the pieces, forming a waterproof seal around the edge. Rainwater is then directed toward roof drains, and away from any place where it could leak and provoke damage. 

These features are made of thin metal - commonly galvanised steel - designed to direct water away from critical roof areas. Every connection of the roof plane and a vertical surface needs to be surrounded with capping, to ensure that water will run down its sides and be directed away from the surfaces. That includes walls and roof features such as chimneys, skylights, and vents.

Application

Corrugated roof flashing can be used anywhere the water has to run off. That includes roofs, chimneys, skylights, doors, windows, spouting and gutters.

Roof Flashing Types

The choice of available types of flashings and cappings is broad and diverse enough to suit any kind of roofing style. 

• Continuous roof capping: Also known as “apron flashing,’ this type consists of a single long piece of metal. Adequately placed, it conveys water down to the shingles, tiles and slates. Its downside is low flexibility due to the length, so it’s important to look for models with a built-in expansion joint.
• Base flashing: This type is ideal for places requiring two or more pieces of flashing, such as chimneys. Along with added security and easier installation, chimney flashing features the benefit of good flexibility. Its joints will contract and expand naturally as the weather changes, keeping the entire system well-sealed. 
• Step flashing: A rectangular piece, used in layers with shingles at wall-to-roof connections. It’s bent 90 degrees in the centre and installed along the full length of the sidewall, partially exposed. For that reason, copper cappings are a popular, aesthetically pleasing choice.  
• Kickout capping: Customised pieces for bridging the gap between the gutter and step flashing endings directs water away from the wall. 
• Skylight capping: This customised feature is often available from skylight manufacturers or included in the package. It’s also possible to purchase it separately. 
• Counter-flashing: This part completes the system, installed either opposite or above the base capping.
• Valley flashing: Open valleys capping is made of metal and designed specifically for the protection of the area where roof slopes meet.
• Drip edges: Small pieces of thin metal constructed to protect the edges and navigate the water drip further away from the protected areas.
• Ridge flashings: roofing materials used to seal the gap between two roof slopes at the ridge.
• Saddle flashings: roofing materials used to prevent water leakage around roof penetrations such as pipes and chimneys. They are shaped like a saddle and are made of metal or rubber.

Roof Flashing Materials

The traditional material for capping is lead or lead-coated metals. Today, however, the selection is broader and suited to different roof designs. That being said - building codes in some areas might limit the available choice. 

• Aluminium: Lightweight and easy to work, it’s a material of choice for many installation professionals. On the downside, it’s slightly sensitive, particularly to contact with alkaline surfaces. Coated aluminium can be used with concrete and masonry without such risk. Additionally, a layer of coating is strongly recommended in coastal and humid areas as a way to prevent corrosion.
• Steel: Galvanised steel is preferred by many due to its corrosion resistance. It’s also flexible and visually appealing. 
• Metal: Metal flashing is a durable and corrosion-resistant roofing material used to prevent water from penetrating the building envelope and can also add a decorative element to the roofline.
• Copper: Copper flashing is durable, long-lasting, flexible and suitable for bending, which all makes it an excellent material to use around chimneys. Its main downside to some is also considered an advantage to others - copper discolours into a patina.

Sealants

A sealant is a necessary element of roof capping. Although nails are commonly used to secure the metal in place, they can be hammered only to one surface, either to the vertical wall or roof plane. Otherwise, if used on both sides, the material would be exposed to intense pressure and probably deformed. Nailed only to the one surface and sealed, the capping can stay secured while the other materials and elements expand and contract during the seasonal changes. 

• Roofing cement: Applied with a towel, it creates a waterproof seal. 
• Modified bitumen roofing tape: This modern, watertight material is used to aid roof flashing. 

Maintenance

It’s best to perform a thorough annual inspection. Damaged or rusted elements need immediate replacement. 

Keeping these elements in their best condition can spare the property owner of other costly roof repairs, preventing future issues before they happen. 

Things to Consider Before Buying Roof Capping and Flashing

The roof is functional as much as it’s adequately built and well-protected. Installing roof capping at every potentially weak spot, such as a wall, chimney, or in open roof valleys, will determine the quality and life span of the roof and, subsequently, the actual value of the investment.  

Old capping doesn’t always require replacing when the new roof is installed. If the metal is in good condition, free of damage, rust, and corrosion - it’s good to go. 

Similarly, new flashing can be installed on an old roof to strengthen its protective properties. The surrounding shingles, however, need to be removed for the installation and then placed back, provided that they are in good condition.