do they _need_ ceiling ties to stop the spread or do the purlins stop the spread as well as sagging? as seen on another thread, i need to evacuate the roof space in my garage in order that i can use my car lift to its full hight. atm, the ceiling joists prevent the car from going up very far at all, so they need to be removed. the roof is a 45degrees tiled, with
2be3inch rafters at 400mm centers, with 3be9inch pulins half way down. the purlins are themselves supported at 2.5m spans by 4be4inch posts dropping down to an rsj. i had a mate round yesterday who is a civil engineer and he said that he thought the because the roor has purlins, you dont _need_ the ties that natraly form the ceiling, so that would solve one problem. next problem is increasing the span of the purlins from 2.5m to 6.5 or 7 meters without support. he suggested increasing the strength of the purlins with flitches ie steel plates bolted to both sides of the purlin for most of its length, or failing that replacing the wood perlins with RSJs. i am still waiting for the architect to come out so i am still bouncing ideas about on the best way to solve the problem!steve