For professional builders and remodelers, the business view from the deck is looking good. That’s because economic conditions point to a 4.6% increase in the number of decks that will be installed this year or roughly 158,000 more deck jobs nationwide, according to Metrostudy, an expert on residential construction data and a sister company to JLC.
While builders are interested in the economic view, customers care more about the actual view from their deck — both inside and outside. For many builders, providing customers with the panoramic vistas they demand means using cable infill rather than traditional wood infill. Manufacturers claim the slender stainless steel cables offer a durable, low maintenance alternative to glass or wood.
The look can be particularly attractive combined with wood frames. But cables require carefully constructed frames to meet code and aesthetic demands, and that’s where builders can miss the mark. Here are three of the most common mistakes builders make when constructing wood frames for cable rail infill — and how to avoid them:
1. Frame not rigid enough. Wood frames must carry 200 to 300 pounds of load per cable rail. That’s easily 2,000 to 3,000 pounds of tension on a typical installation. This load is often not evident until the very end, when the cables are tightened up. That’s when a weak frame can bow badly or even fail. To avoid this scenario, start with a strong, rigid top rail of at least 2x6-inch lumber. Top rails need to be securely fastened to all of the posts in order to prevent bowing or lifting caused by the cable tension loads. Also, attach minimum 1x4-inch wood blocking underneath the top rail between posts. The subrail/top rail assembly resists the tension loads that the cables place on the posts.
2. Posts too weak and spaced too far apart. Posts are also crucial to a solid frame, especially end and corner posts which carry the majority of the cable tension load. Start with end posts that are a minimum of 4x4-inch and remember that softer woods such as cedar may require 6x6-inch posts to avoid bowing, especially with 42-inch high railings. Intermediate posts or pickets/spacers carry minimal tension loads because the cables pass straight through without terminating, so these can simply be sized as needed to support the top rail and meet the lateral loads required by building codes. Space all posts and pickets/spacers a maximum of 3 feet apart to minimize any deflection if the cables are forced apart and be sure that the posts are securely fastened to the deck structure. If you’re using cable end fittings that require drilling through your end posts, be sure to space those posts 3 inches to 4 inches from the face of a wall to allow access for attaching the fittings.
3. Cables spaced too far apart. To meet code and provide safety, cables must not allow a 4-inch sphere to pass between them. Even when tensioned, 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 may create a hazard.
For more on how to properly install cable rail infill go to http://www.feeneyinc.com.
