Rafter ties or ceiling joists acting as rafter ties are required by code unless the house is designed so that the walls or a structural ridge beam carries the full load of the roof.
Rafter ties for lean to roof.
Simpson strong tie 6 in 18 gauge triple zinc steel rafter tie.
From a practical perspective it s difficult to use high rafter ties on a low pitched roof because the force in each tie increases with the inverse of the pitch.
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Simpson strong tie category roof truss and rafter connectors ties and straps for cold formed steel construction.
Lean to rafters then connect to a ledger board against a wall of another shed or house.
If you are framing a cathedral ceiling there are a couple ways to deal with the need for rafter ties.
A lean to roof also called a shed roof slopes in one direction with rafters that rest against another structure at their high end and overhang support posts or an exterior wall at their low end.
Simpson strong tie 5 2 7 in 18 gauge triple zinc steel rafter tie.
For pricing and availability.