Roof Diaphragm Blocking

Blocking consists of lightweight nailers usually 2x4s framed between the joists or other primary structural supports for the specific purpose of connecting the edges of the panels.

Roof diaphragm blocking.

Offset roof planes roof framing must keep diaphragm in plane load on diaphragms may be different due to different heights. Common roof framing system is to span 1x nominal boards across rafters. This additional nailing provides a greater number of fasteners available to transfer shear from one panel to another thus increasing the overall shear capacity and rigidity or stiffness of the diaphragm. A horizontal diaphragm element parallel and in line with the applied force that collects and transfers.

A blocked diaphragm is one in which all four panel edges occur over and are nailed to common framing. See figure 2 systems which provide support fram ing at all panel edges such as panelized roofs are also considered blocked. Use vertical blocking you would have to figure out how to get the diaphragm force from the blocking chord to the wall sheathing since the blocking would be held back from the outside face. The reason for blocking in diaphragms.

The perimeter of the diaphragm then must have the ability to transfer loads into the side walls or shear walls. O addition of sheet steel blocking to an unblocked diaphragm apa 2000 o addition of nailing to existing blocked diaphragm allows limited improvement because framing member requirements change at closer nail spacing. To design the roof diaphragm building designers determine the thickness and grade of the roof sheathing the nail size and frequency the size of the supporting framing members and the amount of blocking required. Diaphragm types case 1 diaphragm higher shear values panels perpendicular to floor framing for improved performance cases 2 6 may be preferred for low shear demand where changing framing direction helps hvac runs fire blocking draft stopping n s 4x8 sheathing roof trusses.

Loads in the roof system are transferred through the roof diaphragm which is the structural plane created by the roof sheathing.