Low slope roofing
Hi
I have a low slope roof with a leak. Interior is exposed beams. Built in ‘61. What I have surmised from various roofers and experts…the ceiling files are about 1.25” thick and then there is supposedly insulation board, roofing decking, tar paper and finally the shingles. These are all stacked on top of each other as described….in order to repair the leak….it will involve going in thru the top and I’m pretty sure I’ll need to and should re-roof the back half of the house. 7 year old shingles but I’m convinced that it was a shoddy job and / or shoddy repairs to leaks around the boots. Anyhow, what do you recommend as far as the layer past the insulation board? Decking—OSB or plywood. Then some had said Ice and water the entire roof while aother said double underlayment (what is that exactly) and ice and water only around boots. Slope is 2/12 according to the roofers that have been up there. Love to hear your thoughts. Charlotte NC
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Shingles on a 2/12 are bound to leak. Mine did, since the day house was built in 1970. Since that portion of the roof is not visual, I did EPDM. I personally did I&W above and below all penetrations and the usual on the edges. Felt, foam, rubber. 3 layers of foam with offset seams, offset downhill, cause I am paranoid.
15 years no leaks, so fingers crossed seems to have worked.
If you can see it and just must have shingles[I cannot blame you, who wants to look at rubber] I would be tempted to I&W the whole thing at that pitch. My front side is a steeper pitch so I did the same I&W above and below penetrations, felt, foam, plywood, I&W, felt shingles. Yeah, it used to leak really bad. THis roof faces southish, so I strapped an airspace under the plywood, as my previous experience has been that shingles get heat damaged sitting right over foam. I question the wisdom of that over another inch of foam these days. Your house like mine was probably shingled right over the foam, nailed straight through. With plywood over the foam you now have a permanent reroofable surface so even if the shingles don't last 40 years, it is less of a project to replace them.
I would do EPDM. PVC is another popular choice; I just don't have experience with it.
With EPDM, don't use bituminous products (such as Ice & Water Shield) next to it because it will degrade the EPDM; they are chemically incompatible.
As everyone else has said you should not do shingles. While they technically are rated to that pitch, I would never specify them or put them on my own house at that pitch.
Another option would be a well installed standing seam, with a high quality peel and stick like grace underneath. Though, Even with this you could run into issues if there are any minor install errors or lots of penetrations.
EPDM, PVC, or TPO are good options for monolithic membranes, just make sure you get a designer or installer very familiar with whichever option.
Thanks everyone. I’ve considered metal standing seam. I just don’t feel like I see it enough here on houses and wonder if can find a quality company to do it.
Not knowing exactly what is up there , when I have them pull off shingles and tar paper. I’m sure there will be some
Decking that needs replaced and when that is lifted, I will know for sure what it’s under it as it relates to insulation board. Is it correct that insulation board can be under the roof decking (plywood or otherwise)? I can not speak to how anything. Was done prior to my ownership. I suspect I’m the 3rd owner. Thanks everyone for the advice.
I do not have a firm idea about your roof construction. 'In general' insulation is above the structural roof deck. There may or may not be an additional nailing surface above the foam, as I have on the front of my roof.
If you went with a rubber roof, the sequence from inside to out would be:
structural roof framing[beams rafters]
structural roof deck
any air water barriers etc, sheet products
foam
EPDM, PVC roofing of choice
with shingles it may be the same or there may be a sheet of plywood over the foam for the shingles to nail to.