Metal Box's Factory in Arbroath opened in the early 1960s and is still in use, although now occupied by a different company, Presentation Products. It stands in full view of the ECML just across the Dundee Road on the western approach to the town, facing open parkland and the sea. Originally it was served by sidings fed from a reverse spur off the old Carmyllie branch, which left the ECML at Elliot Junction, just down the road.
Rather than produce the factory in one huge unit, I've split it up into modules so that you can create your own factory as well as the original, by using whichever parts suit. Normally you'd need at least a front and back unit, two side walls and a roof unit. The original is six units long and three roofs deep, with side walls only at the extremities.
The roof unit is the same length as the basic side wall and the same width as the front and rear units to keep construction of the main building simple. It has different facings on front and back, as on the prototype, although I've 'knocked' the colour down a bit (the prototype roof is very white, which just looks wrong in model form) and changed the skylight layout so that one unit can be repeated as needed.
The screenshot shows the front and back facings of the roof, plus another 'exploded' version of the unit's construction. In the prototype, the roof lines up exactly with the ends of the side walls and is a straight continuation of the rear wall, but overhangs the front (so the front units need to be set back a couple of feet if you want to capture the character accurately).