Curved construction

Factors to consider with curved aluminum extrusions
By Dave Johnson
September 22, 2009

The Milwaukee (Wis.) Art Museum’s Quadracci Pavilion features a custom triangular curtain wall system that had to be curved to a compound elliptical configuration. Photos courtesy of Mid-Am Metal Forming.

Curved glazing and sweeping architectural accents transform ordinary buildings into distinctive landmarks used by architects and contractors alike as showpieces of their craft. There is an innate understanding that buildings are straight; curved means custom fabrication. Glass is a flat polygon, aluminum is extruded as lineals and standard fabrication equipment is designed to measure in a straight line. As such, when complex curved designs make their way to contractors, the prospect of making the architect’s vision a reality can be daunting.

Below are a few common conditions to be considered when bidding a project requiring curved aluminum extrusions.

Material finish. While it is possible to curve pre-finished material, pre-anodized material may show crazing or fading, and forming pre-painted material will void most manufacturers' standard paint warranties. The ideal process is for mill-finish material to be formed, and the curves to be finished afterward. Check with your forming contractor to see if they offer finishing services.

Thermal properties. In storefront applications, thermally broken, thermally slotted, insulbar and thermal clip systems are all available. The best quality formed product of those listed is the thermal clip system. While the others are all able to be formed, the thermal resin might crack during forming, the slotted material might segment or break at the slots, and the insulbar could come loose, split or cause the parts to sit out of square to one another. With the insulbar type system, it is possible to form the assembly as separate pieces, then pull and crimp the insulbar itself after forming.

Environmental concerns. Some common forming and finishing systems use hazardous materials, such as lead or chrome, in the process. The material can be contaminated and might cause issues on Leadership in Energy and Environmental Design projects and in jurisdictions that limit these toxins. Our company uses the LeedArch forming and finishing model that eliminates Environmental Protection Agency regulated chemicals from our material processing. Check with your forming and finishing contractors on any environmental contaminants used in their processing.

All of these considerations should be discussed with the curving contractor as early as possible in the estimating phase of a project. By relying on the expertise and experience of a qualified specialist in the curving industry, many of the common pitfalls and uncertainty involved with curved designs can be avoided, making your next curved project more lucrative and problem free.

The author is president of Mid-Am Metal Forming, Rogersville, Mo.