Fan Fold Foam as Underlayment

Fred Johlin
5/17/2008
We purchased Pro-Snap roofing system from MidWest Manufacturing in a light color to enhance the energy use by our home. We had planned to keep the old asphalt shingles on and per the manufacturing instructions cover them with fan fold foam insulation and then put the steel roofing down. We got three quotes to install the product and two of the quotes were for tearing off the old shingles and putting down new felt as the only option. They stongly stated that they never install over an existing shingles but alway rip off the old and start with a fresh deck. The third quote is still pending. One of the roofers was concerned about the safety of walking on the fan fold foam on a 7/12 pitch roof while the other did not want to do any work that was not "the best" and therefore would not install over the old shingles. The old roof is still sound and could last another 5 - 10 years based on the projected life span when they were installed. Why the strong opinions? Why would the manufacturer provide one suggestion for installation with the fan fold insulation while the roofers feel so strongly to start with a fresh stipped deck and fresh felt? Fred
Guest User
5/18/2008
have you been to this companies website? It says it's designed to be installed over a flat roof deck. Heck it's a 28 gauge 16 inch panel, The contractors that have giving you bids to tear off the old asphalt shingles and felt sound like they care about what they are doing. You could see alot of deflection in the panels if you don't. As far as the fan fold foam you don't need it in my opionion, why their website claims it an energy star rated panel.
Guest User
5/18/2008
Yes we did look at the web site before we purchased the system. The Fan Fold was to smooth out the surface and yield giving a flat appearance. The energy star rating is based on the fact that light colored metal roofs reflect more heat than they absorb while asphalt roofs absorb more heat than they reflect. 28 guage is thin material but it seems than most residential roofing is 26 to 28 guage and that it is more the quality of the steel is more important than the guage of the steel. I was wondering if anyone has used this construction technique with the fan fold insulation and if they are happy or unhappy with the results. My motivation was: Why put more items in the landfill if there is no real need to tear off the old roof? We are trying to make our foot print in the environment as small as possible not as big as possible. Fred
Todd Miller
Classic Products, Inc.
5/20/2008
The risk is that, if the panels press into the fan fold at all or if they are not very careful to keep all the fasteners torqued the same, you could cause deflection in the panels that will be unsightly or even cause leaks and possible wind uplift. I would consider something more like a "recovery board" rather than fanfold over the shingles. Check with a local roofing distributor. They should have such a thing.
Guest User
5/24/2008
Thank you for the information.
Todd Miller
Classic Products, Inc.
5/29/2008
You're welcome.
Guest User
5/30/2008
Well I have tried to find the recovery board for this job. One company will not sell it to individuals (Flex Green Guard PB6W) and for the local distributor would only order this for me if I order 60 square. They will then only sell it to the contractor if he is verified on the installation practices. WHAT A HEADACHE this has become. I was trying to avoid adding to the land fill when there was no solid reason to tear off the old roof and possibly even a small benefit to leaving it on but now I am not certain. The Firestone product looking a fan fold foam but it is a green colored foam. The a different local distributor told be to just purchase blue board foam and use that, but that seems to be the same issue... deformed if the screws are too tight. What is the big deal about not selling to the end user but only to contractors? What is the big installation "deal" with Flex PB6W? GOSH Fred
Guest User
5/30/2008
Hey fred another option is using 1x4's spaced at whatever the manufacture of the metal suggest. and then laying a synthetic underlayment over that then your metal.
Todd Miller
Classic Products, Inc.
6/11/2008
That is another option. Roofing distributors often do not like to sell around the contractors who support them.
Guest User
2/26/2009
Hi there, what did you wind up doing? I have a tar and stone roof (with a good pitch, no problems there) and also want to keep the existing roof on and go over it with fanfold-- but I'm going to look into this recovery board that was mentioned to see what that is all about.........
Guest User
2/27/2009
Rebshar, Even though it has been a while since Fred posted he said he wanted a "solid reason" to remove the old roof. He stated the answer to his own question. The 'solid reason' is a solid deck. You will get a better, smoother job if you remove the old roof.
Guest User
9/6/2009
I'm just installing a new metal roof and put Ice & Water Shield on the whole thing and it turned out swell. If I were to replace a roof, I would always remove the under layer for a better finish that will last the complete life cycle of the product and more. Anyhow, if your thinking your saving the enviroment your wrong because after your long gone the new owners may replace the whole roof metal and ashphalt in all.
Todd Miller
Classic Products, Inc.
9/6/2009
Keep in mind that the metal roof is always 100% recyclable.
Guest User
9/23/2009
Did you get the Menards Pro Snap 28 gauge as well?
Guest User
9/24/2009
I am in the middle of a shingle-to Pro Rib metal swap myself (1st roof job I've done, but I've done other carpentry in the past;) and I had to give the literature to the inspector/"building permit guy" to review to tell whether thye could OK a steel roof as I'll be the 1st in my subdivision with other than shingles. They OK'd it, with these stipulations; (1) I was planning on going over the shingles too as the Pro Rib literature suggested this; but they required me to strip it down. (2) I had to go with the Ice n Snow barrier around the whole perimeter as well as down the valley (I have an L shaped house with a hip roof) Actually I'm glad I did as I found alot of bad/questionable decking that I wound out replacing, and due to the fact that the "short leg" of the "L" was added on some time after the house was built, they put another ridge up and instead of pulling out the original hip rafter and going solid, from sill to ridge, they just "tied into" that original hip rafter, causing a severe sag, in line with that hip rafter. So I replaced 11 rafters, solid from sill to ridge, w/o the "seam" in between. Making for alot better job. and doing this myself, instead of calling in a contractor, made it easier to aford to do it right!
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