How to Use GALVALUME® for Your Metal Roof

Published August 29, 2016 by Whirlwind Team

 galvanized metal roof

One of the best features of a metal roof is its durability. Making a good thing even better is GALVALUME®.

You may have heard of GALVALUME while searching for metal roof materials. It’s a specific galvanized sheet metal product coated with a mixture of aluminum and zinc alloy with a touch of silicon. It was developed by Bethlehem Steel in 1972, and nearly all large steel manufacturers produce it using their patents.

GALVALUME® is only one trademarked name for the material and the process; others include ZINCALUME (Steelcase, LLC) and Galval, Cincalum, or Zintro-Alum (Ternium USA and Ternium Mexico).

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GALVALUME production

GALVALUME is produced through a continuous hot-dip process in which coils of cold-rolled steel are laid out, cleaned, and welded into one long piece. The sheet is placed on a coating line that can run as fast as 600 feet per minute and moves the sheet through the hot dip process.

Once the sheet is coated and finished, it is re-coiled around a reel until used. 

What is so great about GALVALUME roofs?

Included amongst the many benefits of GALVALUME roofs, they are durable, even more so than a bare steel roof.

The coating on a GALVALUME roof panel provides significant outdoor corrosion resistance. In fact, the coating is projected to last about nine times longer than galvanized steel with an equivalent thickness of coating.

Existing GALVALUME low-slope roofs in the eastern United States have been found to be in excellent condition and are predicted to last at least another 50 to 60 years before requiring major maintenance.

GALVALUME is easily roll-formed into a variety of panels or formed and stamped into tiles and shingles. If you want the color to last, purchase panels that have been factory painted. GALVALUME is a light-weight, strong, all-around great roofing material.

Recommended roof types for GALVALUME panels

In residential metal roofing , pre-painted GALVALUME is typically used. It can be placed as a new roof or retrofitted over an old one. Some architects and builders use unpainted GALVALUME for its bright metallic surface, perfect for reflecting away sun and heat.

For non-residential roofing, low-slope, concealed fastener standing seam roofs are best made of unpainted GALVALUME. A low-slope standing seam roof with concealed fasteners is an excellent replacement for non-metallic built-up and ballasted roofs. It can also be used to replace steep-slope screw-down roofs with exposed fasteners.

Steep-slope architectural roofing and mansards can be covered with pre-painted GALVALUME to enhance the building with color, form, and texture. For both non-residential uses, GALVALUME can retrofit both old steel and non-metallic roofs or placed as a new roof.

Reflectivity benefits

GALVALUME has terrific reflectivity, of both heat and sunlight. Ideally, you would use bright white pre-painted panels for maximum reflectivity. It will efficiently reflect away the sunlight, reduce the heat transmitted to the building, and keep it much cooler inside. Your electricity bill should show substantial savings.

Testing shows GALVALUME roofs only transmit about half as much heat into a building as galvanized steel roof panels and only a third of the heat transmission of terracotta roofs. In colder seasons, the heat is reflected back into the building to keep it warmer at a lower cost in the winter. You have energy savings year around.

Beware of pressure treated wood

First of all, it is definitely not recommended to place bare or pre-painted GALVALUME panels in contact with wet wood. Anything that holds moisture against the panels diminishes the durability of the material by prolonging contact with a corrosion-causing substance.

Pressure-treated wood, in particular, is no good for GALVALUME roof materials. The chemicals used to treat the wood enhance fast metal corrosion. These corrosive chemicals leach out of the wood and accelerate the corrosion process.

Never use pressure-treated landscape ties either in direct contact with the roof or in a place where drainage off the pressure-treated lumber could pour onto the roof panels. When HVAC and other roof ancillaries are roof-mounted, be sure to use the factory-supplied mounting accessories that are compatible with GALVALUME. Do not use pieces of lumber or other wood as a foundation between the ancillary and the roof.

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Let’s talk about costs

A new or retrofit GALVALUME standing seam roof over a traditional non-metallic roof can provide both direct and indirect savings.

If you retrofit a GALVALUME roof on a light-weight structural system with an old leaking non-metallic roof, the initial cost is lower on almost every other alternative besides tearing the pre-existing roof off. Then, with the new metallic roof, long-term costs are contained with low maintenance needs and longer life.

If you want to save even more, a GALVALUME roof is readily insulated.

If you start with a traditional flat, non-metallic roof such as a built-up, you will have a higher initial cost for a new low-slope GALVALUME standing seam roof, but you will still save in the long term for the same reasons of low maintenance and longer life span.

To be clear, GALVALUME is not the same as galvanized steel. It is better. The coating process patented by Bethlehem Steel nearly 45 years ago remains the industry standard today for galvanic coated steel panels. GALVALUME can be sourced from all major steel manufacturers, including those near your jobsite.

A roof made of GALVALUME will withstand any weather and maintain its good looks and the ability to reflect sunlight and heat away from the building in summer and back into the building in winter, creating significant cost savings for homeowners and commercial building owners alike.

The low maintenance and long life increase the cost savings because there is little need for major repairs or maintenance with normal wear and tear. Factory pre-painted panels retain their color, further providing savings because there is little need to repaint.

The galvanic coating of GALVALUME even resists corrosion in areas where the panel has been cut or scratched; making GALVALUME a recommended material for high-slope, exposed fastener roofs as well.

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