Lead and copper have been used to weatherproof buildings for centuries, and when it comes to roof flashing they still stand as the gold standard for flashing materials. However, with the economy in the toilet and the prices of heavy metals increasing consistently, scrap metal theft has become a worldwide problem, with bold metal thieves literally tearing the sheets of valuable metal flashing from the roofs of buildings.
Needless to say, if you're a victim of flashing theft, you probably won't want to replace the missing flashing with another sheet of valuable metal, and will be casting around for alternatives.
However, if you need to repair or replace your roof flashing because of ordinary wear and tear, you should also be considering alternatives to lead or copper—modern flashing materials can be just as effective as the traditional choices, as well as less expensive and, crucially, less desirable to thieves.
Strong and highly resistant to corrosion and rust, stainless steel is a fine choice for roof flashing, and while by no means cheap, it is significantly less expensive than either copper or lead. Stainless steel flashing is also unusual in that it is relatively malleable, making it easy to work with. Terne-coated stainless steel is a more expensive option, consisting of stainless steel coated with a lead-tin alloy to further reduce the incidence of corrosion, and also mimic the appearance of genuine lead.
However, stainless steel comes with a couple of drawbacks. While stainless steel is highly corrosion resistant, it is not immune, and areas that do not experience adequate rain flow can become corroded over time. This can be avoided with the use of the aforementioned terne coating, and also with polymer weather treatments. It can also be extremely noisy during heavy rains or hail, and should be fitted with a cushioning underlay.
What is sold as zinc roof flashing is actually almost always an alloy, consisting mainly of zinc but also containing strong, non-reactive metals such as titanium and copper. This combination provides superior weather and corrosion resistance at a price comparable to stainless steel. Zinc flashing is available in a variety of pre-applied finishes and patinas to reduce its reflectiveness, reducing its already low value to metal thieves.
The main problem with zinc is that it cannot be installed on a roof with aluminium or steel fittings. Even a simple, exposed steel screw will, when put in prolonged contact with zinc sheeting, cause a rapid and destructive chemical reaction in the zinc that drastically reduces structural integrity and can cause serious leaks.
Ethylene Propylene Diene Monomer (EPDM)
EPDM is a strong, waterproof rubber membrane, applied as roof flashing in large, continuous sheets. EPDM marries low prices with great durability and weatherproof qualities, and does not crack in extended periods of heat or sunshine like other rubber alternatives. EPDM has no value as scrap for obvious reasons, and is laid in a much less visible fashion than metal flashing; a well laid EPDM liner should be totally obscured by tiles or concrete.
Unfortunately, no variety of rubber or plastic flashing has the long-term durability of lead, copper or other metals, and EPDM flashing will eventually begin to degrade and puncture; this process will be hastened on a steeply-sloped roof. A building with EPDM flashing can also be sweltering in summer, as the rubber traps more heat and humidity than alternatives. EPDM is also non-recyclable, making it a poor choice for ecologically-minded homes.
Learn more about these options by contacting resources like Hi Tech Roofing.