Structural Porch PostsNovember 10, 2017
Three Common Questions (and Their Answers)
In porch projects, getting the posts right can mean the difference between a structurally sound porch and one that puts people in harm’s way. In serving contractors, the three most common questions we hear from our customers are:
What are the load tolerances of Superior Plastic Products porch posts?
Superior has done extensive testing to determine their posts’ “point of failure” (i.e., the absolute maximum amount of weight their posts can hold). To ensure safety, the typical rule of thumb is to not attempt supporting any more than half of that maximum load. For example, Superior’s max load rating on 4” posts is 7,800 pounds, so you would not want to support more than 3,900 pounds with them.
The max load ratings for other-sized Superior Plastic’s porch posts are below:* • 4.5” posts = 11,800 pounds (appropriate for supporting up to 5,900 pounds in your projects)
5” posts = 10,500 pounds (appropriate for supporting up to 5,250 pounds in your projects) • 6” posts = 18,000 pounds (appropriate for supporting up to 9,000 pounds in your projects)
With Superior Plastic Products load testing results, we’ve found them to be more than adequate in serving most porch projects’ requirements.
What are the load tolerances of pressure-treated wood posts?
Quite often, we’re asked how much weight a 4 x 4 or 6 x 6 pressure-treated wood post can hold. The answer to that question isn’t always straightforward. Many different factors affect the load tolerances of wood posts, including the length of the unbraced height, the type and grade of wood, the service conditions, and other variables. According to calculations using an online “Capacity of Wood Column Calculator” by Jonathan Ochshorn via Cornell University, a southern SPF wet-service 4 x 4 9-foot-long post can hold about 3,500 pounds and a 6 x 6 9-footlong post can support about 10,000 pounds.**
What does code require?
Unfortunately, no answer exists to this question. International Residential Code (IRC) offers guidance on platform and balloon frame construction, but not on the construction of posts and beams.
With building codes not specifying the weight a post must bear, you’re left on your own to figure it out, unless you’re working off an architect- or engineer- The Good News Even though the future remains uncertain for Clubhouse decking, you can rest assured you will still have all your needs met by Homestead Outdoor Products. We have other high-quality decking material options available, including those from WOLF Home Products, Paldeck®, and Fiberon®. approved plan. To ensure posts are adequate, make sure you know the expected dead-load and snow-load capacities. And when in doubt, consult an engineer.
* According to Superior Plastic Products’ website— accessed 9/29/2017
** This information is not meant to replace the expert advice of an engineer. While the online calculator’s
information appears to make sense, we cannot guarantee its accuracy