How much joist spacing do you need between your deck framing?
One major reason your deck could fail sooner than expected is due to poor framing. Having a solid frame is key to an even decking surface that doesn’t bow over time.
As a rule of thumb, most decks will require 16″ on center joist spacing, which means there is 16″ from the center of one joist to the other.
Beyond that, there are three things to consider when deciding the spacing on your deck framing.
First is the decking material. Composite and softwood decking will follow the 16″ on center rule, but hardwood decking can handle greater spans with similar dimensions. For example: 5/4 x 6 cedar can span 16″ on center, but Ipe can be a 1 x 6 dimension for the same span. 5/4 x 6 Ipe can actually span 24″ on center.
Decking Material Thickness
This brings me to the second thing to consider: the thickness of the decking material. Most composite brands have the same thickness, but softwoods and hardwoods will range from 1″ to 2″ thick for decking. Softwoods should be at least 1 1/4 inches thick for a 16″ on center span. 2 inches thick will allow for a 24″ on center span. 1″ thick Ipe will have a 16″ on center span, an inch and a quarter will have a 24″ on center span, and 2″ thick can have a 32″ span.
Surface Board Angle
The last thing to consider when figuring out the correct joist spacing is the angle of the surface boards. If you are laying the boards at a 45-degree angle to the framing then you need to shorten the span. 16″ on center would drop to 12″ on center, 24″ would become 16″ and 32″ would become 24″ on center. If you are installing a commercial project, it can be a good idea to shorten the framing spans as well since the deck will have significantly more traffic.
These considerations are just guidelines, so reference your local building codes for specific span and spacing ratios.
This tip-filled post comes courtesy of Austin NARI member TimberTown.