Dan,
The bracing that Rockwood places in the roof is not very strong. The weight of the material can sag over time. The added weight of an A/C unit can hasten the sag. You simply measure by spanning the two sides of the roof with a straight object. A 2x6 or 2x8 on edge will work. You then just simply see how much space you have under the board edge.
I agree. 4" sounds pretty bad.
Vin.
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2015 HW296
2006 HW256 (previous pup)
2013 Chevy Tahoe
Equalizer WDH 10000#
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