To start off, when people talk about a tin roof, it rarely means that they are actually talking about a roof that is made entirely from tin. Like a steel roof, a tin roof is usually made up of multiple types of soft metals and coated with an extra layer of protective material to ensure the roof will last for an extended period of time. In many cases, tin roofs are made of steel and coated with a material known as terne or terneplate* which is a combination of metals that includes tin, lead and zinc. To determine if this type of roof is right for your home, check out the pros and cons of tin roofs below.

Pros

• Affordable: One of the major draws that a tin roof has is the affordability of the material. Unlike copper or aluminium, or even galvanized steel, a tin roof coated with terne is among the most affordable types of metal roofs on the market. Although it is less expensive, this type of coated metal roof can actually last for a longer period of time than an aluminium or a galvanized steel roof, as long as it is properly installed and maintained. With a regularly maintained coat of paint, an iron roof coated in terne can last up to 90 years*, making it one of the most cost effective types of metal roof available anywhere.
• Weather/Heat Resistant: While it is true that all metal roofs are extremely well suited to resisting the elements, and most can keep your house from getting too warm while it is under the hot sun, some materials are better suited than others. A traditional coated tin roof can actually provide a homeowner with weather and heat resistance that is comparable to the most expensive materials that are currently on the market. In fact, a terne/ternplate coated roof can actually do a better job of reducing the midday peak temperature of a house in the summer than a regular steel roof, due to the improvements made in the coating itself. The increase in the zinc content in terne coated roofs has greatly contributed to this, and has also made this material more a more environmentally sustainable option.* Make sure to hire proper roofing contractors.

Cons

• Modification Difficulties: Metal roofs like this one are often installed as large sheets placed directly on a rooftop, usually over existing shingles. This can sometimes become an issue when it comes time to repair or replace a sheet, should it ever become damaged. Even if the repair cost is covered under a homeowner’s warranty (which it likely would be in the case of a tin roof like this), it is sometimes difficult to find the exact same materials that were used on the roof decades earlier. This is especially true with composite tin roofs like this, since the metallic mixture of the roof’s coating is subject to change based on the availability of materials.
• Regular Maintenance: For a tin roof to get the maximum lifespan, it is important to make sure the roof is well looked after over its entire lifespan. While some metal roofs require little to no maintenance, such as a copper roof, a tin roof will need to be painted regularly to ensure it doesn’t succumb to weather and heat damage prematurely. Before you decide on this type of roof, be sure to take the additional cost of regular maintenance into account.

*Info Source: http://www.motherearthnews.com/green-homes/metal-roofing-pros-and-cons-zmaz84mazgoe.aspx?PageId=1
http://inspectapedia.com/roof/Terne_Metal_Roofing.php
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