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Aluminum Rails

Aluminum rails are a good option for customers who want the sleek unobtrusive look of metal without the corrosion associated with steel. Most aluminum rails receive a factory-applied powder-coat finish that is tougher than conventional paint.

Frequently used on commercial and multifamily projects, aluminum systems are usually tested to both the IRC and IBC standards. Aluminum is considered a conventional building material in the code, so aluminum rails do not require special approval and are often available with tempered glass infill (see “When a Guardrail Contains Glass”)

When a Guardrail Contains Glass

Though permitted by the IRC and IBC, tempered-glass infill poses problems for vinyl and composite railing systems. If the guard contains glass, the glass and the rails require a four-times safety factor, so the rail must be tested to 800 pounds (200 pounds x 4) and the glass to 200 pounds (50 pounds x 4). Tempered glass can pass this kind of testing, but many railings cannot — at least not without being thicker, shorter, and more expensive than they currently are.

What’s more, code compliance reports cannot be issued for systems with glass infill, because the test standard contains no acceptance criteria for glass. The lack of a compliance report makes it difficult — though not impossible — to convince the inspector that the system complies with code.

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The balusters in CertainTeed’s Durham system are held in the rails by spring-loaded pins; the compressible rubber end piece prevents rattling.

It’s not possible to issue code compliance reports for composite and vinyl rails with glass infill, so it can be difficult to get approval from the building department for rails with tempered-glass panels (left) or balusters (right).

When asked about the code status of their rails with glass infill, most manufacturers will say the glass complies with ANSI Z97.1 (a standard test for impact resistance) or that the infill is merely “decorative.” Trex took the added step of having an Artisan rail with glass infill tested by an outside lab and can provide a report of how it fared during structural testing. There’s no guarantee that the inspector will accept this report — but there’s no guarantee he’ll accept a code compliance report, either.

If glass infill is a problem in your jurisdiction, you might consider Fiberon’s composite Clear Vision System or Fairway’s Grandview Vinyl Railing System, both of which contain clear acrylic panels. Since the panels aren’t glass, the code treats them like any other baluster material.

Installation. Some products, such as CertainTeed’s Durham, are assembled entirely on site. The Durham balusters fit into precut holes in the rails and are held in place by spring-loaded pins. Once assembled, the rail sections are installed between aluminum posts that are bolted to the deck.

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The Durarail system is made from heavy powder-coated aluminum; here it’s shown with a combination of pickets and tempered glass.

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The Durarail system is ordered to size and arrives partially assembled, with pickets welded between rails that have already been cut to length. The posts and rail cap are exceptionally stout. Durarail is also available with tempered glass panels.

Do Manufactured Railings Meet Code?

Under the IRC, vinyl and composite railings are considered to be an “alternative” material, which means their use is subject to approval by the local building department. Inspectors may ask for proof that the product complies with code, such as stamped drawings from an engineer. In most cases, however, they will be satisfied if you can show them a code compliance report from the ICC Evaluation Service (ICC-ES) or an accredited lab such as Architectural Testing Inc. (ATI). The report affirms that the product has been tested in accordance with ICC-ES AC174 — the Acceptance Criteria for Deck Board Span Ratings and Guardrail Systems. This protocol requires specific tests for durability — resistance to termites, decay, freeze/thaw, ultraviolet, and the like. More significantly, it requires testing of the guardrail system to prove that it complies with the structural requirements of the building code.

How Railing Kits Are Tested

The loads published in the code are design loads. For a manufacturer to meet code, however, the railing system must be tested at a much higher load — at a safety factor of 2.5. This means the top rail is tested to a load of 500 pounds (200 pounds x 2.5) and the baluster infill to 125 pounds (50 pounds x 2.5).

The upper rail is tested in the two locations where it is most likely to fail — at the center of the span and at the post connection (see photos). Testing is performed by installing a railing system between wood posts on a test rack, connecting a cable to the upper rail, and observing what happens as the cable is tensioned to 500 pounds. Infill is tested by pressing or pulling on a one-foot-square piece of material placed against the balusters.

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A 500-pound point load is being applied to this rail to test for compliance with the IBC (left). Balusters are tested with a 125-pound load (50 pounds x 2.5 safety factor) applied over one square foot of area (right).

A rail system passes if no part of it breaks or deflects excessively during testing. Maximum allowable deflection is calculated using formulas referenced in AC174. As an example, a rail 36 inches high and spanning 72 inches between posts would be allowed to deflect a maximum of 2 1„4 inches.

Structural requirement. Table R301.5 of the IRC states that the upper rail of the guard must be designed to withstand a 200-pound point load from any direction and that the infill — the balusters — must withstand a 50-pound horizontal force over one square foot of area. The bottom rail is not considered except insofar as it supports the infill. (Site-built wood rails must be designed for the same loads, but because wood is considered a conventional material by code, wood rails aren’t usually tested. It’s up to the inspector to decide if a particular wood railing is strong enough.)

Most vinyl and composite railings rely on 4x4 wood posts for support — posts for which the railing manufacturer takes absolutely no responsibility. When a manufacturer addresses these posts at all, it’s to give a blanket statement that they must comply with the local building code. Under the IRC, the post must be designed to withstand the same 200-pound load as the rail. The problem is, the code doesn’t explain how to achieve this, which places liability for safe performance of the manufactured railing squarely on the builder.

Lacking guidance, some carpenters use questionable methods to install posts — for example, notching and bolting them to a rim that is merely nailed into place. Notching severely weakens the post, and the lever action of the post can pull the rim free from the joists.

Prescriptive guide. Last year, the American Wood Council took the guesswork out of code-compliant wooden decks by publishing the “Prescriptive Residential Wood Deck Construction Guide” (DCA6). Available for free at awc.org, it contains specific construction details for all aspects of deck construction, including post attachments. According to DCA6, the posts supporting deck rails should be 4x4 or larger, unnotched, and through-bolted to the outside joist using a metal connnector detail like the one developed by Frank Woeste and Joe Loferski in tests at Virginia Tech and published in JLC in 2005 (“Strong Rail-Post Connections for Wooden Decks,” 2/05). Note that since 2005, at least three manufacturers have released hardware specifically designed for attaching 4x4 pressure-treated wood posts to deck framing: DeckLok’s bracket system (866/617-3325, deck-lok.com), Simpson’s DTT2Z and HD2AHDG deck post connector (800/999-5099, strongtie.com), and USP’s DTB-TZ deck tie bracket (800/328-5934, uspconnectors.com). The upshot is that builders can now easily provide strong, tested connections for critical guardrail attachment.

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Though the IRC contains few specific details for attaching rail posts to deck framing, there are several sources now available to provide guidance to builders and inspectors. This drawing is based on research done at Virginia Tech and published in JLC (2/05) and the American Wood Council’s new deck construction guide, DCA6. Approved hardware is available from Simpson Strong-Tie, USP, and DeckLok.

Of course, not all railings are installed on decks: For posts installed on stone patios or concrete slabs, manufacturers offer flanged metal post mounts that attach with masonry anchors.

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For instances when it’s not possible to support rails with wooden posts, most manufacturers sell metal post mounts similar to this one from Azek.

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Most manufacturers can supply secondary graspable rails for use on stairs. The model shown here is from Fairway Vinyl Systems.

Graspable rail. Though the requirement for graspable handrails on stairs is rarely enforced on residential decks, the top rails of most manufactured railings are too wide to comply. If the inspector is strict, however, many products are available with ADA- and code-compliant secondary rails, usually a cylindrical aluminum core with a vinyl cover.

David Frane is a senior editor at JLC.