The Basics of Metals Used in Roofing Today

Most metal roofing products offer the following benefits:
long life, lightweight, low life-cycle cost, rust resistant, fire resistance, design flexibility, recyclability and energy efficiency.

Choosing to install a metal roof is a wise investment for your home. The numerous benefits of metal roofing will protect your home, your belongings and most important, your family for many years to come. Each metal roofing material has varying levels of the above mentioned benefits, so make sure to discuss your specific requirements with your contractor as they will be able help you decide which metal roof material will best suite your needs. Below is a brief summary of five fairly common types of metal used in roofing today.

Steel

Steel is defined as a metal alloy of iron with a small amount of carbon. Different amounts of carbon produce different grades of steel with differing mechanical properties. There are two common kinds of steel used in roofing today. These are galvanized steel and Galvalume steel. Both of these kinds of steel have an anti-corrosive layer added to the steel to protect the base steel from oxidization. Typical thickness is a range from 30 ga to 22 ga For your average residential metal roof, the choice is commonly 30 ga.

The amount of recycled content in North American steel building products is approx. 63% (BOF and EAF steel making processes combined).

The most common types of finishes are pre-painted PVDF (polyvinylidene fluoride), bare Galvalume and/or granular coated.

Some of the unique benefits of this type of metal roofing are that it is the most commonly installed metal roofing product in North America, has endless choices for design, color and finish and is a more economical choice compared to other metal roofing. Steel roofing has a low galvanic reaction and therefore is the least problematic with conflicts between roofing material and flashing or fasteners. Steel is considerably stronger than Aluminium. Steel is the most recycled material on the planet, in large part due to its magnetic ability – which makes separating steel from other construction materials very efficient. Many of the other roofing metals are non-ferrous metals, which are not magnetic.

Stainless Steel

Stainless steel (also called Inox) is defined as a steel alloy with a minimum of 11% chromium content. Typical thickness is 0.4 or 0.5mm.

The amount of recycled content in today's stainless steel can be up to 60%.

Stainless steel comes in many types of finishes including anything from pre-painted stainless to a subdued matte grey finish, to a chemically produced metallic blue, green or red.

Some benefits of this type of metal roofing are that it will not rust, has an extremely high melting point/fire resistance, extremely long life and when used in an unpainted state has zero effect on rainwater run off.

Aluminium

Aluminum is defined as a silvery ductile metallic element found in bauxite. Bauxite is sedimentary rock containing various minerals, often found in a clay form.

Typical roofing thickness is between 0.032" – 0.040".

The amount of recycled content in Aluminium is 80-85%.

The types of finishes available for Aluminium are very similar to the pre-painted options available for steel, including a granular coated finish.

Some benefits of this type of metal roofing are that it performs better that average in a harsh coastal environment, it does not retain heat and Aluminium will not rust.

Zinc and Zinc Alloys

Zinc is defined as a metallic chemical element found in reasonable abundance around the world. It is extracted from mountain limestone and magnesium limestone in conjunction with galena and is often found combined with sulphur. The ore is roasted, mixed with charcoal, and heated in peculiar retorts. The zinc is converted into vapour, condensed, and fused.

Typical thickness of zinc roofing material is approximately 0.7 – 0.8 mm thick.

The recycled content in today's zinc products is at about 30%.

There is no need for any paint or coatings for zinc alloys. When exposed to the elements they naturally and continually build a protective layer (patina) over time and will self repair any incidental imperfections or scratches. Some unique benefits of this type of metal roofing is a well documented history of use in Paris, France (more than 85% of all roofs in Paris utilize zinc, some dating back to 1800's. Zinc roofing is quite malleable and therefore works well for custom roofing projects and it requires much less energy to refine than other metals.

Copper

Copper is a ductile and mouldable reddish-brown corrosion-resistant metallic element. Pure copper is rather soft and a freshly-exposed surface looks pinkish or peachy in colour.

For roofing purposes, the typical thickness of copper ranges from 12 oz. to 20 oz. per/sq.ft.

The recycled content for copper roofing is quite high at approx. 75%.

No finish is required as copper will naturally patina over time.

Some benefits of this metal roofing are that it won't rust, it doesn't require paint, beautiful unique patina finish and will last for a lifetime. The recycled value of scrap copper is typically 90% or more of the value of new copper.

Cost Analysis

A cost analysis of the varying types of metal is difficult to summarize as there are so many options within each type of metal. For the most simple cost comparison, steel and aluminium are similar in cost. Copper, stainless steel and zinc are considerably higher in material cost. When considering the cost of a metal roof, the term 'life-cycle cost' comes into play. This is how much the roof costs over the life of the roof, including installation and maintenance. When you compare the life-cycle cost of a metal roof to almost any other roofing material you soon realize that metal roofing has a low life-cycle cost and will save you time and money compared to most other roofing materials. A properly installed, quality metal roof system should look great and last you a lifetime.