Spent a fair bit of time checking some columns for vertical
Ran a string line - to check for straightness of this edge
Have about 4mm of error on the LHS edge
Came up with a strategy to keep purlin straight
Welded on cleats on stairway beam, and two front beams
Purlin dropped in perfectly.
Drilled holes and bolted in 12 mm galvanised bolts at the cleats
Used Tek Screws at a number of places along the steel framing to secure purlins.