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Flash Forward: Choosing The Right Flashing For Roofing Coastal Properties

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Choosing the right building materials when roofing a property is essential, providing long lasting protection against leaks, damp and mould in the attic spaces of your buildings. However, choosing suitable flashing materials can be more difficult when you are constructing coastal buildings, as the flashing will have to contend with high winds and seaborne storms without degrading under the relentless assault of salt spray.

Fortunately, many conventional flashing materials are up to the task of defending coastal properties against leaks, so you will have some degree of choice when planning and designing your next project. However, some commonly used flashing materials fall short when used in these coastal locations, so familiarising yourself with how different flashing materials deal with coastal conditions is all-important.

Galvanised steel

One of the most types of metal flashing, galvanised steel flashing is inexpensive and relatively easy to install. However, when used to waterproof the roofs of coastal properties, serious issues can emerge. The thin layer of zinc oxide that coats galvanised steel flashing and protects it from rust is very vulnerable to salt spray and high levels of airborne salt, and will degrade more quickly than it would if used further inland. Once this coating has been compromised, the bare steel beneath rusts quickly and can cause damaging, persistent leaks.


This metal, on the other hand, is naturally rustproof, and far more suitable for coastal buildings. Though more expensive than galvanised steel, it is also lighter and can be installed very quickly, and will stand up to storms and heavy rains well as long as it is protected by a robust roof covering. However, you should take special care when installing aluminium flashing, as thin sheets of aluminium flashing can be quite vulnerable to tearing if installed poorly.


The last word in rust-resistant metal flashings, copper flashing is attractive as well as durable, and is particularly well suited for designs that involves large amounts of exposed flashing (such as roofs with multiple skylights). Unfortunately, it is generally consider prohibitively expensive for all but the most well-funded luxury property projects.


PVC is a strong and durable thermoplastic that is particularly popular as a flashing material. In most cases, it excels when used to flash coastal roofing, as PVC flashing sheets have high tensile strength to defend against high winds and are not at all bothered by salt spray. PVC flashing is also very affordable, and can be installed quickly and easily by skilled roofers.

There are a couple of drawbacks associated with using PVC flashing, however. Firstly, it cannot be used with asphalt roofing, as the heat of the asphalt will cause melting and catastrophic damage. Secondly, the material itself is hardly the most attractive of flashing materials, and should be well hidden beneath tiles, eaves and other accents if aesthetics are important to your project.

EPDM rubber

A tough, waterproof variety of synthetic rubber, EPDM sees extensive use as a flashing material, and like PVC it is just as home close to the sea as it is further inland. EPDM is particularly resistant to high winds and storms due to its tremendous tensile strength, and accidental tears occurring during installation are unlikely. Although more expensive than PVC, it is usually cheaper than metal flashing options.

The only real downside to EPDM is its flammability. Although the material will not ignite unless temperatures become extreme, they can contribute to a serious house fire and thoroughly gut the upper floors of a property if allowed to ignite. You should therefore factor this flammability into the fire safety plans for your properties.