- Q. I know blocking is needed in the mid-span area of a floor system. But is blocking necessary along the end-joist since this member is supported by the foundation and the subfloor?
A.I would recommend blocking along the end-joist just as you would in the rest of the floor system. If the floor is blocked only in the middle, the end-joist can tip if the foundation is displaced at any time. This can bulge the exterior sheathing or put a dip in the floor.
Blocking is often installed as an afterthought by a helper, but once the floor is decked, it is hard to get the block into the joist cavity near the foundation. As a result, end-blocking is usually left out. For this reason, the blocking should be installed before the subfloor.