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Zinc roof fails in 18 months!

My new roof has now got palm size holes and white powder where the zinc was. What has happened? There are patches over most of the roof and the zinc has literally disintegrated into white dust and the sheeting around it has become very thin. Please let me know if you have any ideas? This is not galvanised metal, it is purely zinc.

Matt Lewis
home owner - England
May 23, 2008

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Hi, Matt. Sorry, I am not personally familiar with zinc roofs, although I understand that they have long been used in Europe and the life expectation can be 40 to 100 years. Is there any other metal touching the zinc? Is there anything unusual about the exposure (limited exposure to fresh air, for example) that is preventing the natural growth of the zinc patina and causing this white rust to form instead? Is this a standard roofing material from a supplier who makes it for roofing or did you get the supply from somewhere else? Is there runoff from concrete landing on this roof section, or another source of acidic or alkaline water? Do you have any previous experience with zinc roofs?

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
May 22, 2008

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Pretty rare to find a pure zinc roof in the UK. Much more common are zinc flashings, ridge caps etc for galvanized sheet steel roofing material, but this is rarely used on housing, more for commercial buildings.

Zinc is highly reactive and one of the oxidation products is white powder. Sounds like your roof has turned to zinc carbonate. But why?
Sounds most unusual. Must involve some acidic substance or something. As Ted says, Galvanized steel will last from 40-100 years. But zinc should last as long.

Geoff Crowley
Crithwood Ltd.
Westfield, Scotland, UK

May 27, 2008

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Dear Friends,
Titanium Zinc is a material which is affected from water or acids. If you have not enough slope, then there is a problem under titanium-zinc layer to hold the water drops which causes the zinc salts. Also the pH degrees of the material under this material also causes to this white zinc salt. please be careful to use yellow pine tree (which is neutral pH) or use epoxy coated titanium zinc which protect from water or the material which has acidic or basic effect like EPDM on roof layers.

Muharrem Gursoy
- Istanbul, TURKEY
September 3, 2010