An end joist is the final floor joist within a framing system, positioned at the very edge of the floor’s span, running parallel to the other joists in the system rather than perpendicular the way a rim joist does at that same edge.
Because it sits at the perimeter, this joist sometimes carries slightly different loading conditions than joists positioned entirely within the interior of the floor system, particularly if the floor edge supports additional structure like a balcony or cantilever.
Understanding the distinction between an end joist and the perpendicular rim joist enclosing that same edge helps avoid confusion when discussing floor framing details with a contractor.
What Does an End Joist Involve?
- Standard joist material matching the rest of the floor system
- Positioning at the outermost edge of the joist run
- Connection to the rim joist at that perimeter
- Potentially different loading if the edge involves special conditions
Why Are End Joists Important?
An end joist supporting a cantilevered section, like a bay window or a small deck extension, may need to be sized or reinforced differently than a typical interior joist, since it can experience different loading patterns than joists supported at both ends by standard bearing. Recognizing when an end joist condition requires special engineering attention, rather than assuming standard joist sizing applies uniformly, is an important part of accurate floor framing design.
Doubling the end joist, using two members fastened together rather than one, is a common practice specifically at floor edges supporting additional load, like where a stairwell opening or other structural condition concentrates extra weight near that perimeter.
End Joist vs. Rim Joist
An end joist runs parallel to the other floor joists, positioned at the system’s edge. A rim joist runs perpendicular to the joist ends, enclosing that same perimeter and providing the connection surface for the wall framing above.