Framing: Defining "On-Center"

Construction jargon can be confusing as a homeowner or DIY'er when a contractor or inspector starts spitting out all kinds of random words and terms related to your project. It's especially intimidating when they are telling you what you need to do, but you have no idea what they mean! (I feel the same way when my wife starts talking about marketing - it flies right over my head! It's like she's speaking a whole different language!)

Here I wanted to dive into what "on center" is in reference to as it relates to framing so that next time you hear that term, you'll know what exactly they are talking about and how it might affect your project.

On-center defines the separation of framing members (beams, studs) with a repititive, consistent measurement pattern. Typically this involves the studs in walls, floor joists in a floor system and trusses, rafters and ceiling joists in a roof structure. Normally when these components are built they are placed every 16, 19.2 or 24 inches apart, also known as on-center.

Sounds pretty simple right? If you have seen any framing you have probably seen wall framing studs at 16 or 24 inches on center, while rafters and engineered trusses normally are placed at 24 inches on-center. It also references that the beam is measured from the center of the beam to the center of the next beam, rather than inside one beam to the outside of the next.