Roof Truss Blocking

It is important however to understand that this blocking creates the structural boundary members for the roof diaphragm and it is not optional.

Roof truss blocking.

Roof trusses attach to a ledger that is on top of a block wall. Each block is 2x4 or 2x6 depending on the size of the rafters and is secured to the top plate. The ledger is needed to properly attach the perpendicular roof trusses to the top of the structure. For trusses with heel heights less than 15 this blocking can be made of solid sawn dimensional lumber as shown in figure 1a.

A ledger is a horizontal board that is attached to the top of the the wall. A new provision in the 2009 irc and carried through to more recent versions is the use of blocking panels between roof trusses to connect the trusses to the braced wall panels below if the heel height is greater than 9. With trusses one truss makes up two planes so it s already tied together on a handstack roof you need that sheeting to tie one plane to the hip and from the hip to another plane. A true stick framed hip is bearing a truss hip not so much.

The lay in is good enough. Depending on the building codes in your area you may be required to install blocking up the rafter sections towards the hip of the roof a requirement designed to further secure truss systems against lateral movement. Tabulated allowable diaphragm lateral design loads contained in the building code are based on testing of unblocked and blocked diaphragms structural wood members used at intermediate sheathing edges to increase the shear load in the diaphragm.