Roof Diaphragm Blocking

Tongue and groove edges panel edge clips one midway between each support except two equally spaced between supports 48 inches on center lumber blocking or other.

Roof diaphragm blocking.

Apa s diaphragms and shearwalls l350a has a good set of tables showing the strength of various blocked and unblocked sheathing methods. 2306 2 3 double diagonally sheathed lumber diaphragms. An unblocked diaphragm has no requirement for blocking between unsupported edges of adjacent panels. You then provide double the nailing requirement at the blocked bays.

Diaphragm and becomes one of the connections from the roof diaphragm to the shear wall. For 1 2 inch panel maximum span shall be 24 inches. There is an unquantified load path resistance interaction present. Gypsum board diaphragm ceilings shall be in accordance with section 2508 5.

Similar changes to 2306 3 for shear walls. Which a blocked diaphragm can be designed are many times greater than those for diaphragms without blocking. Only lumber blocking shall satisfy blocked diaphragm requirements. Shear forces acting on heel block the building designer may not assume that prescriptive heel blocking will perform adequately as perimeter blocking for the roof diaphragm especially if unsure of the blocking material or how it is being installed.

Double diagonally sheathed lumber diaphragms shall be designed and constructed in accordance with af pa sdpws. 2306 2 4 gypsum board diaphragm ceilings. It also states you could stagger the blocking in a blocked diaphragm allowing vents every other truss bay. The three major parts of a diaphragm are the web the chords and the connections.

Since the individual pieces of. If this were framed the way i would typically do it the unblocked but staggered roof diaphragm would have 240 allowable shear where with their method it would be 180. To roof diaphragm at top and to foundation at bottom roof horizontal diaphragm carries load to end walls. I think on a typical residential roof the rafter and certainly the truss is the primary bending resisting member and that the osb sheathing is the diaphragm element as long as rafters and blocking keep the diaphragm from buckling and properly transmit the load components up into the diaphragm.

It is important however to understand that this blocking creates the structural boundary members for the roof diaphragm and it is not optional. The 200 pounds of uplift force allowed by the irc does not take into account the nailing between the trusses the blocking and the top plate when blocking is provided.