3 Best Practices for Cable Rail Wood Frames that Stand the Test of Time

Remodelers who think they don’t need to offer decking may want to change their view. Economic conditions point to a 4.6% increase in the number of decks installed this year or roughly 158,000 more deck jobs nationwide, according to Metrostudy, an expert on residential construction data.

Additionally, homeowners are investing more in outdoor spaces than ever before with 85% of those renovating opting for a major remodel or a complete overhaul, according to the 2017 U.S. Houzz Landscape Trends Study.

Today, many remodelers use cable rail infill on railings rather than traditional wood infill when renovating or adding decks to connect interiors with exteriors — and give customers the panoramic views they demand. Manufacturers say the slender stainless steel cables offer a durable, low maintenance alternative to glass panels or wood balusters.

The look can be particularly attractive combined with wood frames. But cables need carefully constructed frames to avoid bowing and possible failure, not to mention callbacks and bad word of mouth. Here are three best practices for constructing wood frames that support horizontal cable rail infill — and stand the test of time:

1. Construct a solid frame. Wood frames must carry 200 to 300 pounds of load per horizontal cable. That’s easily 2,000 to 3,000 pounds of tension on a typical installation. This load is often not evident until the cables are tightened and a weak frame bows badly or even fails. To avoid this scenario, start with a strong top rail of at least 2×6-inch wood or 5/4×6-inch for hardwoods like Ipe. To prevent bowing or lifting, top rails need to be securely fastened to all posts. Attach 1×4-inch wood blocking underneath top rails between posts for additional compression reinforcement to keep posts plumb. If adding a bottom rail, space it no more than 4 inches above the surface of the deck or as required by code.

2. Size and space posts properly. End and corner posts, which carry the majority of the tension load, are especially critical. Start with end posts a minimum of 4×4-inch and remember that softer woods such as cedar may require 6×6-inch posts, especially with 42-inch high railings. Intermediate posts or pickets carry minimal tension loads, so these can be sized as needed to support the top rail and meet code-required lateral loads. Space all posts and pickets/verticals a maximum of 3 feet apart to minimize deflection if cables are forced apart, and securely fasten posts to the deck structure. For cable end fittings that require drilling through end posts, space posts 3 to 4-inches from the face of a wall for room to attach the fittings.

3. Space cables to code. To meet code and provide safety, cables must not allow a 4-inch sphere to pass between them. Even when attached to a properly designed frame, each cable can deflect as much ½-inch if forced apart. Therefore, they should be spaced no more than 3 inches apart to account for their flexibility. Even with the most rigid frame, any spacing larger than 3 inches may not meet code and could create a hazard. Remember, straight runs of cable, no bends, dips or rises, can extend up to a maximum of 70 feet before terminating, while runs with bends, up to two corner bends at most, should not exceed 40 feet.