Delivering Architectural Aesthetics and Sustainability with Extruded Aluminum Trim

Extruded aluminum trim can add architectural distinction to both the interiors and exteriors of a wide range of building types as well as complement moisture management systems

January 2017

Design Aesthetic

Manufactured to work as an integrated/complementary system with the major U.S. manufacturers of cementitious or fiber cement siding and multiple other cladding solutions, extruded aluminum profiles are available in variety of choices. Their design, mostly driven by architects seeking cleaner details, adds a distinctive profile to interiors and exteriors of buildings. In addition, it breaks up the monotony of flat panel walls where the same siding products are used repeatedly. Installing aluminum trim rather than using wood trim or cutting and ripping fiber cement boards or panels is more convenient and saves time. “Using trim over panel joints becomes an architectural element and is a way of expressing the joints and defining their deliberate placement. It adds a level of architectural refinement,” says Russell A. Hruska, AIA, principal and co-founder of Intexure Architects in Houston. In our climate, stucco often requires additional oversight to be correctly executed. Aluminum trim, when used with fiber cement panels or lapped siding, is more cost effective than stucco and provides long-term durability while achieving our design aesthetic.”

Shown here is a private residence in Houston (Architect: Intexure).

Photo courtesy of TAMLYN

Extruded aluminum adds durability and longevity to a wide range of construction projects. Shown here is a private residence in Houston
(Architect: Intexure).

Constructed from 75 percent to 100 percent post-industrial and post-consumer scrap, extruded aluminum trim meets requirements for sustainability and can contribute to LEED^® recycled content points. It may also be specified for interior or exterior use. Applications include an increasingly wide range of building types wherever fiber cement panels or lap siding is specified. In recent years, extruded aluminum trim has begun to replace traditional wood 1x2 and 1x4 trim on single-family homes and is increasingly preferred for multifamily structures.

Extruded aluminum trim products are intended for design aesthetics. They do not include an exterior insulation and finishing system (EIFS)—a type of building exterior wall cladding system that provides exterior walls with an insulated finished surface. Manufacturers usually state if their product does or does not include an insulation system. Since some extruded aluminum trim products on the market incorporate an EIFS, design professionals should note the exact description of each manufacturer’s product and its performance expectations. As a general rule, extruded aluminum trim products that are not part of an EIFS system are not designed or intended to be used in conjunction with an EIFS or similar system.

Nor do architectural trim profiles form a complete moisture management system. Always a critical feature of construction, a moisture management system is the province of the architect and builder who are responsible for designing and installing a code-compliant building envelope. Again, manufacturers usually point out that extruded aluminum trim alone does not include a complete moisture management system, despite the fact that trim is designed with drain dams for vertical runs and shingle fashion for horizontal profiles. Some manufacturers do, however, supply moisture management products that complement their trim line and additionally help meet code requirements (see below).

Design professionals are also advised to consult with the siding manufacturer for best-practice applications of extruded aluminum trim product in order to ensure color, dimensions, and thickness match.

Prefabricated Trim Materials

Extruded aluminum adds durability and longevity to construction that other trim materials, such as galvanized steel and polyvinyl chloride (PVC), lack (see sidebar Benefits of Extruded Aluminum).

Galvanized Steel

While initially less expensive than extruded aluminum, galvanized steel is less durable. The use of bare mill galvanized steel and aluminum flashing in direct contact with most claddings will increase chances of a chemical reaction, causing wear and break down on both products.

Polyvinyl Chloride (PVC)

The third-most widely produced plastic and the least expensive also has limitations compared with extruded aluminum. One manufacturer of extruded aluminum trim profiles developed and manufactured PVC trim profiles to use with fiber cement siding and soffits, and it still does. But through learned experiences and public demand, it began converting its profiles into more durable extruded aluminum. One-hundred percent vinyl trim is susceptible to swelling and buckling when exposed to direct sunlight. Moreover, PVC trim with painted dark colors, which is increasingly the choice of architects and developers, may cause the product to warp. This comes about because excess solar heat, especially in hot climates, may be absorbed, subjecting the PVC to distortion due to extremes of thermal expansion and contraction. Paint adhesion loss, blistering, and peeling may also result.

Characteristics of extruded aluminum trim include:

It adds a design aesthetic to a wide range of building types.
It offers multiple profile choices.
It’s typically fabricated from custom die-extruded heavy-duty 6063 T-5 aluminum alloy with a coating that protects against harsh weather conditions and allows for paint adhesion.
It’s typically designed to match color, thickness, and dimensions of the country’s major cementitious siding manufacturers and multiple other cladding options.
It’s available in anodized, standard color palette, or ready-to-paint finishes
It’s a sustainable material comprised of 75 percent to 100 percent post-industrial and post-consumer scrap and can contribute to LEED recycled content points.
It replaces time-consuming cutting and ripping of fiber cement panels or boards for trim use
It can be used for interior and exterior weather conditions.
It’s highly durable and will long outlast caulk
It poses no health or physical hazard. (Aluminum trim products are defined as “articles” by the Occupational Safety and Health Administration and are therefore exempt from the requirement of publishing material safety data sheets.)

BENEFITS OF EXTRUDED ALUMINUM

The most abundant mineral in the earth’s crust, aluminum is derived from bauxite, which is mined from the earth. After processing, the resultant alumina undergoes a smelting and alloying process that produces solid logs of cast metal from which extruded aluminum shapes or profiles are made. Most extruded shapes for architectural use are fabricated from AA 6063, an aluminum alloy, with magnesium and silicon as the alloying elements. Type 6063-T5 aluminum, commonly referred to as the architectural alloy, has a very smooth surface and is the best alloy suited for anodizing applications. The T5 designation indicates it has been artificially aged and moderately heat treated. Aluminum extrusion is a highly versatile metal-forming process that has a wide array of physical characteristics, including:

It can be recycled and retains a high scrap value. It can be recycled indefinitely without losing any of its superior characteristics, making it especially appealing according to both environmental and economic criteria.
It’s lightweight. It weighs about one-third of most other metals, which makes it easier to handle and less expensive to ship.
It’s strong. Profiles can be made as strong as needed for most applications. Having the strength of a rigid metal prevents swelling and buckling.
It’s weather resistant. Cold-weather applications are particularly well served by aluminum because, as temperatures fall, aluminum actually becomes stronger.
It’s fire resistant.
It does not rust because aluminum is protected by its own naturally occurring oxide film.
It’s resilient and can spring back from the shock of impact.
It’s not combustible. Even at extremely high temperatures, it does not produce toxic fumes.
Different finishes are available. It can be finished with liquid paint (including acrylics, alkyds, polyesters, and others), powder coatings, and anodizing.
It offers seamless profiles. Complex shapes can be realized in one-piece extruded aluminum sections without having to employ mechanical joining methods. The resultant profile typically is stronger than a comparable assemblage and less likely to leak or loosen over time.
It can be joined in many ways. Extruded aluminum sections can be joined by all major methods in use today.
It’s economical because it’s relatively inexpensive and may not require long lead times. Even short-run prototypes often can be produced at moderate cost.
It can be easily manufactured to accepted standard dimensional tolerances.

CASE STUDY: ALUMINUM TRIM FOR PREPARATORY SCHOOL

Photo of Peak Preparatory School in Dallas.

Photo courtesy of TAMLYN

Extruded aluminum trim painted black accents the reveals in the facade to bring variation to the fiber cement panel.

Photo courtesy of TAMLYN

At the corner, a reveal corner (see below) was used to accent and give depth.

Peak Preparatory School in Dallas, developed for Uplift Education and designed by HKS Inc., is a steel frame construction with a combination of brick and fiber cement panel and lap sidings. Premanufactured extruded aluminum trim in multiple finishes was used to accent corners in the lap siding and to create a varied and interesting facade with the fiber cement panel.

CASE STUDY: MANY USES OF ALUMINUM TRIM FOR NEW HOPE HOUSING INC.

Photo of P4114 Perry affordable housing facility in Houston.

Photo by Hiebert Photography, Houston

New Hope Housing used extruded aluminum trim for window and door headers; to terminate between fiber cement and brick or stucco; to accent the fiber cement; and on corner conditions.

Photo of the building's interior corner.

Photo by Hiebert Photography, Houston

Extruded aluminum trims were used for horizontal, vertical, and corner conditions for fiber cement panels and for the corner and transitions in the fiber cement lap siding.

The new 4114 Perry affordable housing facility in Houston, developed by New Hope Housing Inc. and designed by Val Glitsch, FAIA, LEED AP, Houston, is a three-story wood construction on a concrete foundation. The exterior is a mix of brick, stucco, fiber cement panels, and lap siding. Premanufactured aluminum trim was placed above, below, and between the different types of fiber cement siding, above windows and doors, and below the siding over brick. It also was used for both inside and outside corners and where panels meet the lap siding boards. “The alternative to premanufactured trim? Wood trim gives a very different aesthetic. It is bulkier and, for water infiltration concerns, can only be used for vertical joints,” Glitsch says. “We could have had a metal shop make up the trim pieces, but that’s not always a good way to get a quality, consistent, cost-effective product. And the heavier-weight ‘extreme trim’ we used makes it easier to install the product properly.”

Trim Profiles

Most profiles in the industry are fabricated from custom die-extruded 6063 T-5 aluminum alloy; trim profiles have a coating that protects against harsh weather conditions. Since siding panels will expand and contract due to changes in temperature, a ¹/₈-inch gap should be allowed between panels and trim.

Manufacturers typically warrant defective-free products for a period of 10 years for the original purchaser unless otherwise stated for the specific product ordered. They are further warranted as to adequacy of design, provided products are properly specified and installed.

Examples of trim profiles include:

Vertical bead reveal
Horizontal bead reveal
Panel inside corner
Vertical reveal
Reveal outside corner
Reveal inside corner
Vertical board reveal
Bullnose outside corner
Bullnose inside corner

Vertical and Horizontal Bead Trim

Vertical and horizontal bead trim each serve as an expansion joint between panels. Horizontal trim is designed to work as a system with vertical bead trim. Both work with all panel profiles and finishes.

Diagrams showing vertical bead reveal design features.

Image courtesy of TAMLYN

Vertical bead trim provides a look similar to an open joint while providing a flashing joint.

Diagrams showing horizontal bead reveal design features.

Image courtesy of TAMLYN

Horizontal bead is designed to work with vertical bead, forming a consistent look.

These aluminum trim profiles are not part of an exterior insulation finishing system (EIFS) and not designed or intended to be used in an EIFS or similar system. They are designed for fiber cement or wood panels only.

Panel Inside Corner

A minimal inside corner provides a flashing without calling too much attention to the detail.

Image courtesy of TAMLYN

Inside corner extruded aluminum eliminates the need for a wood corner piece.

Vertical Reveal

Designed for wood and steel stud construction, the aluminum trim provides a reveal for both lap and panel siding, while also serving as rustproof flashing between planks and panels. Plank and panel reveals should not be used for horizontal joints.

Image courtesy of TAMLYN

Vertical reveal provides a consistent shadow line between materials while covering the cut ends for a cleaner finish.

Reveal Outside Corner

Extruded aluminum reveal corner profile offers an alternative to the more familiar closed-corner trim. It can be used with both lap and panel siding.

Diagrams showing reveal open outside corner.

Image courtesy of TAMLYN

With the panel outside corner profile, dimensions of trim used with panel siding are slightly smaller than those used with plank siding

Reveal Inside Corner

Diagrams showing reveal open inside corner design features.

Image courtesy of TAMLYN

The reveal inside corner profile maintains the consistent shadow of the other profiles in the group.

Vertical Board Reveal

This profile provides a broad vertical accent for siding while not extending beyond the face of the cladding.

Image courtesy of TAMLYN

Vertical board reveal is a wide break that can add a distinctive look to a wall and combine with many different horizontal and vertical profiles.

Bullnose Outside Corner

This profile provides a uniform rounded corner to panel applications.

Image courtesy of TAMLYN

Panel bullnose outside corner profile has a unique rounded look.

Bullnose Inside Corner

The bullnose inside corner profile adds a distinct rounded corner for panel installations.

Image courtesy of TAMLYN

A clean, rounded interior corner adds a unique look for panel installations.

Trim Finishes

Extruded aluminum trim is typically available in standard color finishes or primed ready to paint, and also in anodized finishes.

Precolored

Manufacturers recommend one of the standard palette colors because each is made to the exact standards of the largest U.S. cementitious siding manufacturer. The fully engineered paint-coating system is computer matched, fade resistant, uses no volatile organic compounds (VOCs), and is expected to last eight years.

Custom Color

Design professionals requiring custom colors can specify a primed ready-to-paint finish. Manufacturers typically provide a painting guide and recommend following a paint manufacturer’s instructions for an eco-friendly, sustainable, recyclable, fire-resistant, direct-to-metal (DTM) paint material. Aluminum does not rust. It can, however, corrode if its protective coating is uncovered. Manufacturers recommend recoating trim after making end cuts or if there are surface scratches.

Example of custom-patterned extruded aluminum trim.

Photo courtesy of TAMLYN

Examples of custom-patterned extruded aluminum trim

Custom Pattern

Design professionals can also order trim in a custom pattern. In one example in an airport interior, the wallpaper pattern was repeated on the aluminum trim covering panel joints in order to provide a continuous unbroken appearance.

Clear Anodized Finish

A clear anodized finish is an electrochemical conversion process that deposits an oxide film on the aluminum trim. While a natural oxidation process occurs on bare aluminum, producing the controlled oxidation process artificially creates a thicker, harder, and more durable “oxide film.” Clear anodized is an extremely durable finish and is resistant to most forms of corrosion. Design professionals should note that clear anodized finishes can vary slightly from one piece of trim to another and should consider this characteristic before ordering.

Special Color Anodized Finishes

Manufacturers also offer special color anodized finishes if required. Typical colors are gold, black, and bronze. Again, design professionals should note that finishes can vary from one piece of trim to another. Typically, the color of the anodizing will fall within a certain range, which usually can be determined prior to anodizing. The manufacturer should provide anodized color details upon request. Specifiers should require that anodized coating thickness be tested in accordance with ASTM B244-68.

Keeping Moisture Out

Walls with cladding leak just like masonry walls and must drain and dry moisture since water is the most significant factor in the premature deterioration of buildings. Leakage paths exist at any opening in the wall surface, whether intended or unintended. Joints between materials and around windows and doors, vents, cracks, and porous surfaces are all potential entry points for water. As mentioned above, trim manufacturers either recommend or offer moisture management products that help meet code requirements.

CASE STUDY: ALUMINUM TRIM WITH DRAINABLE WRAP FOR STUDENT HOUSING

Photo courtesy of TAMLYN

At Texan 26 in Austin, Texas, extruded aluminum is used with the fiber cement panel to create a reveal system and is installed over a drainable wrap product for moisture management.

For Texan 26 student housing, located just minutes from the University of Texas in Austin, the building exterior is a mixture of fiber cement panel and lap siding. The builder utilized a drainable wrap below the various siding materials in conjunction with a rainscreen at place. According to Jon Standley, president of Motivado Development Group Inc., “A drainable wrap was chosen for the effectiveness under multiple siding products and for maintaining its gap once installed.”

Code Requirements

The International Residential Code (IRC) 2015 states: “Section R703 Exterior Covering: R703.1 General. Exterior walls shall provide the building with a weather-resistant exterior wall envelope. The exterior wall envelope shall include flashing as described in Section R703.4. The exterior wall envelope shall be designed and constructed in a manner that prevents the accumulation of water within the wall assembly by providing a water-resistant barrier behind the exterior veneer as required by Section R703.2 and a means of draining to the exterior water that enters the assembly. R703.4 Flashing. Approved corrosion-resistant flashing shall be applied shingle-fashion in a manner to prevent entry of water into the wall cavity or penetration of water to the building structural framing components. Self-adhered membranes used as flashing shall comply with AAMA (American Architectural Manufacturers Association) 711. The flashing shall extend to the surface of the exterior wall finish.”

Housewrap and Rainscreens

Exterior walls performance requirements are included in the 2015 ICC Section 1403.2: “Weather protection: Exterior walls shall provide the building with a weather-resistant exterior wall envelope. The exterior wall envelope shall include flashing, as described in Section 1405.4 The exterior wall envelope shall be designed and constructed in such a manner as to prevent the accumulation of water within the wall assembly by providing a water-resistive barrier behind the exterior veneer, as described in Section 1404.2, and a means for draining water that enters the assembly to the exterior. Protection against condensation in the exterior wall assembly shall be provided in accordance with Section 1405.3. (1405.3 Vapor retarders as described in Section 1405.3.3 shall be provided in accordance with Sections 1405.3.1 and 1405.3.2, or an approved design using accepted engineering practice for hygrothermal analysis.)”

Housewrap

The primary insurance of moisture mitigation for the building envelope is housewrap that is specifically designed to allow water or moisture to drain. There are several advantages to using an integrated wrap/drainage product. These include requiring no additional installation step and no design change to the wall/siding assembly. One type of housewrap on the market eliminates excess moisture from an exterior wall by providing drainage space between the housewrap and exterior sheathing. This is achieved by bonding very small spacers to the wrap.

Photo courtesy of TAMLYN

Shown here is an example of a moisture management housewrap with 1.5-millimeter spacers that provide a drainage space between the sheathing and cladding material

Rainscreen

Another option for meeting code requirements is a rainscreen system. A rainscreen is a moisture management technique for controlling rain entry in an exterior wall. It generally comprises an air space immediately behind exterior cladding plus a water-resistive barrier that wraps the building wall assembly. The air space that is created by the rainscreen between the back of the cladding and the face of the water-resistive barrier is designed to reduce the forces that draw water into the assembly. Water that does reach the back of the cladding drains from the wall assembly via the space created by the rainscreen. In addition to the drainage capabilities, a rainscreen system also helps accelerate the drying of water vapor that accumulates in the interior wall assembly by moving air throughout the air space. There are several rainscreen options available, including:

Installing “weeps” in masonry construction. “Weeps” or “weeper holes” are small openings left in the outer wall as an outlet for water inside a building to move outside the wall and evaporate.

Constructing a rainscreen wall using furring strips that space the cladding away from the wall. This provides a vent space that helps to dry the back of the siding. Traditionally, layered tarpaper and flashing behind the furring strips created what is called a drainage plane. Now housewrap is more commonly used than tarpaper.

Rainscreen products can be batten strips in the form of plastic slats typically 1¹/₂-inch by ¹/₂-inch placed on top of the housewrap.

Image courtesy of TAMLYN

Shown here is an example of a rainscreen strips product used to create a cavity between the cladding and building wall assembly

The ICC 2015 Section 1405.4 states: “Flashing. Flashing shall be installed in such a manner so as to prevent moisture from entering the wall or to redirect it to the exterior. Flashing shall be installed at the perimeters of exterior door and window assemblies, penetrations and terminations of exterior wall assemblies, exterior wall intersections with roofs, chimneys, porches, decks, balconies and similar projections and at built-in gutters and similar locations where moisture could enter the wall. Flashing with projecting flanges shall be installed on both sides and the ends of copings, under sills, and continuously above projecting trim.”

Flashing

Aluminum has long been the flashing of choice because it is widely available, inexpensive, lightweight, and fairly easy to handle. A coil of aluminum trim coated on both sides with a paint system that is specifically formulated for residential applications will serve most residential and light commercial applications.

Precut and preformed profiles designed for siding, counter, brick ledge, window, and other areas have the advantage of being available in custom sizes and colors that match trim and siding.

Diagram showing aluminum butt joint flashing.

Image courtesy of TAMLYN

Aluminum butt joint flashing is precut and easily installed

Image courtesy of TAMLYN

Shown here is an example of aluminum butt joint flashing with strips of EPDM rubber, which diverts water downward

Sustainability and LEED Credits

Beyond aesthetics and performance, extruded aluminum architectural trim can offer a number of sustainability features and environmental benefits. Extruded aluminum trim products are typically made from 75 to 100 percent post-industrial and post-consumer scrap. They can contribute to LEED credits in categories MR Credit 4: Recycled Content and, in some regions, MR Credit 5: Regional Materials of the U.S. Green Building Council’s Leadership in Energy and Environmental Design (LEED) certification, 2009 for New Construction and Major Renovations.

MR Credit 4: Recycled Content
1–2 Points
Intent: To increase demand for building products that incorporate recycled content materials, thereby reducing impacts resulting from extraction and processing of virgin materials. Requirements: Use materials with recycled content such that the sum of postconsumer recycled content plus half of the preconsumer content constitutes at least 10 percent or 20 percent, based on cost, of the total value of the materials in the project. The minimum percentage materials recycled for each point threshold is 10 percent recycled content for one point; 20 percent recycled content for two points.

MR Credit 5: Regional Materials*
1–2 Points
Intent: To increase demand for building materials and products that are extracted and manufactured within the region, thereby supporting the use of indigenous resources and reducing the environmental impacts resulting from transportation. Requirements: Use building materials or products that have been extracted, harvested or recovered, as well as manufactured, within 500 miles of the project site for a minimum of 10 percent or 20 percent, based on cost, of the total materials value.

*Note: MR Credit 5: Regional Materials applies only in Texas.

Conclusion

Available in a number of configurations, extruded aluminum trim can add architectural distinction to both the interiors and exteriors of a wide range of building types. Typically manufactured to work as a system with cementitious or fiber cement panel or lap siding, it is more convenient and easier to install than trim made from wood or fiber cement panels and saves labor time. Since aluminum is 75 percent to 100 percent post-industrial and post-consumer scrap, it is also sustainable and can contribute to LEED recycled content points. While it is critical that design professionals understand how to incorporate water and moisture management systems in building design, they should be aware that trim products by themselves do not necessarily include moisture management or insulation systems.

Tamlyn manufactures Xtreme Trim™, which consists of sustainable extruded aluminum profiles for fiber cement and other materials. Xtreme Trim™ profiles are designed to work together as a system to create an aesthetically attractive and durable appearance. www.xtremetrim.com