A reader's Roofs and roofing question: Corrugated iron join?

Howard L.   from   Warrnambool. Australia   had this Corrugated iron join question.

Corrugated iron join - Method using a flashing under the joint.

Corrugated iron join - Method of bending the iron.

Bill's reply

• first method is to use a flashing, I have shown a steel purlin here, but quite often there is a timber fascia.
• Some people just turn up the pans of the lower sheets, then push them under as far as they can. Which is not much if there is still a fascia there.
• The best way is to drop the lower roof a few inches and have a vertical section to the flashing, but I still undo the bottom row of screws and put the flashing on top of the batten.
• Note! This is the best method for deeper profile roof sheeting. The bending method below only works with corrugated iron.
• My preferred method is to to it like the bottom sketch.
• If the job is adding the lower pitched roof to a n existing roof then sometimes unscrewing a couple of rows of fixings on the top roof is needed to lift the sheets enough to get the new ones under.
• If the whole roof is new then this is the way to go.
• Put the lower rows of screws in first and the ones going through both sheets last.