This question was triggered by the following line in a home inspection:
Blocking is not installed for I joists above beams in basement.
I have found pictures of blocking at http://www.diychatroom.com/f14/sister-studs-ceiling-easy-question-11349/ (linked from Floor Joist Blocking). I have also found that cross bracing is an alternative to solid blocking. According to the National Wood Council's Details for Conventional Wood Frame Construction:
Adequately nailed subflooring will maintain the upper edges of floor joists in proper alignment. Nailing the ends of joists to band joists or headers provides additional joist support that, under normal conditions, eliminates the need for intermediate bridging.
I feel like I understand the term, and what must be done, but my wife understood the inspector to mention load distribution in relation to the supporting steel beam when he commented to her during this portion of the inspection.
Is my understanding of blocking missing something? Does the possibility of compromising the positioning or structural integrity of the steel support beam exist because there is no blocking?
Best Answer
Blocking typically refers to the structure that prevents the joists from twisting, which would be a concern over a load bearing beam. A solid piece of wood, often the same material as the joists themselves, is installed perpendicular to the joists without any gaps (e.g. I joists would use a piece of I joist for blocking). Two 2x4's installed in an X could also be done, and I've seen that with engineered joists, but check with your local building codes to be sure it complies.
I could also see blocking refer to additional vertical members (2x4's) to carry the load from the beam up to another load bearing object above the floor (e.g. a column). The last type of blocking I can think of would be fire blocking to prevent fire from traveling through the ceiling between parts of the home, though it's unlikely you'd see this requirement in a single family structure outside of a garage.
Like Tester101 says, call the inspector and ask for clarification, they should be happy to provide it.