Roof Truss Blocking

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.

Roof truss blocking.

A ledger is a horizontal board that is attached to the top of the the wall. A true stick framed hip is bearing a truss hip not so much. The lay in is good enough. For trusses with heel heights less than 15 this blocking can be made of solid sawn dimensional lumber as shown in figure 1a.

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

Roof trusses attach to a ledger that is on top of a block wall. The ledger is needed to properly attach the perpendicular roof trusses to the top of the structure. Walls that are constructed of concrete block that need to be covered with a roof will require the use of a ledger.