There are many variables to consider. That particular panel really requires a pretty smooth substrate. I assume they are trying to achieve that using the fanfold but then enters in my concern about over driving fasteners into the fanfold, especially on that type of panel. If you installed over battens, the battens would need to run horizontal and I am not sure if they approve of that. You don'd want to do anything outside the manufacturer specs. Right off hand, as long as it doesn't violate their specs, I would suggest tearing off the old shingles, installing underlayment (you might want to look at the synthetics rather than 30 lb felt) and then the roof. If the current shingles are in exceptionally good shape, you might get by with going over them, along with a new layer of underlayment. I am glad that the attic has good ventilation; if not, we'd have some other things to work through.
Todd Miller
2017-09-01 04:52:10.000000
Good Morning,
I am looking at purchasing/installing a ProSnap hidden fastener metal roof on my house (manufactured by MidWest Industries, sold by Menards). Our house has one layer of asphalt roofing, attic is well ventilated with 10" of insulation. The underlayment is solid.
I would prefer installing over the current roof vs tearing off, but their published recommendations on installation recommends installing 1/4" fanfold insulation before installing the metal roofing in this scenario. Based upon what I've read in these threads, that doesn't sound like good advice due to possibility of roof leakage with insulation bend. Do you have another recommendation for roof preparation? Would installing vertical battons with 30# felt over them be the best option? Or would it be better with this product to remove my current layer before install?
Thanks in advance for any advice!
