Double paper

I finished the roof the day before Hurricane Isabelle hit. Winds only hit 80mph or so. Did another near the beach. 3/12 pitch. No damage to it either. 6-7 nails per shingle.>>>

Building code here will not allow shingles to be overlaid on the end laps . No how no way. The code enforcement will make you cut them flush or t/o . The times they are a changing. Now gather round roofers the new codes are beyond your command Your old road is Rapidly agin'.Please get out of the new one If you can't lend your hand For the times they are a-changin'. The line it is drawn The curse it is cast The slow one now Will later be fast As the present now Will later be past The order is Rapidly fadin'.And the first one now Will later be last For the times they are a-changin'. >>>

It's interesting, isn't it Ciak? :laugh:>>>

BTW, it's fine to lap slate. :cheer:>>>

Yep that is why I make the statement I'm sitting on the fence of this once great industry .>>>

I believe you and I are on the same page. :)>>>

If I am using the term right...I "dutchlapped" a repair on a school before. There was a dip in a beam and the right and left beam was 8 inches higher. The dip was about 8 ft wide...created a river just about...overlapped several inches to prevent water moving horizontally under the next shinle. The center shingles, we sealed each side of the key way. THE DISTRICT WASN'T READY TO PAY TO ADUST A 40 FT BEAM.

DID I JUST "DUTCHLAPPED"? I DIDN'T FEEL LIKE A GOOD ROOFER AFTER THAT! ITS HOW THE CO. WANTED IT THOUGH!>>>

That's STOOOPID!! What's next? Seal every nail head and the laps of the felt? At least it would serve a REAL purpose! lol By the way #15 felt should be outlawed! lol>>>

Hate to be a troublemaker, but this is how I see it. Two layers of 30# would be silly, mainly because it's so thick and moisture sensitive that when it buckles the shingles will heave. Two layers of 15# on pitches below 4/12 are a good idea because they work. Been there and seen it. Same for synthetic. A two-ply system offers leak-proofing benefits that a single layer will never offer. Not one on one. Two plies laid shingle fashion. As Jet would say, "believe me." We all have our rights to our opinions of course. Nobody is going to change my mind on this one. I have seen the difference too often to count. Been right down there with my own eyes and tools and scratched my own head and thought about it long and hard. Again and again. It's a great code, no matter what anybody at GAF says. I am unimpressed with GAF staff for any number of reasons. This is just another one to add to the list. Water has surface tension galore. That is the only hint I'm going to give. You guys are too smart and too experienced in too many ways to belabor the point. I believe in this case, anyone ridiculing the concept of a two-ply underlayment is just plain wrong. So there.>>>

egg; I get your "surface tension" hint, and it makes perfect sense....However, I too have formulated my opinions over the past 30 years based on real-life experiences; Thousands of asphalt composition roofs installed under my supervision, as well as many experiences correcting inferior work of others. I'm not a proponent of the two-layer, (dry-laid, shingle fashion or not), underlayments for asphalt shingles.

I could be all wet here, (no pun intended); I recall, years ago, (couldn't tell you if it was the UBC, local bldg. dept., or a standard manufacture reccomendation), asphalt shingle roof assemblies between, pitches less than 4/12 to 2/12 were allowed, provided the shingles were installed "double-coverage". Most everyone interpeted this as double underlayment, when it actually was referreing to the shingles themselves.....This made perfect sense...Later the "code" or reccomendation wording evolved/was changed to specify the underlayment.....A valid technique was pushed aside via hearsay/public "opinion".......Can anyone validify this?...Or was I dreaming?

I remember working for a small roofing contractor, (aprx. 1980), who religiously installed two layers of felt under asphalt comp. shingles on these nearly-flat, (1/12), patio roofs attached to 4/12 main-house roof. A fairly typical design at that time. I recall getting reprimanded once for cutting all the buckles out of the felt so as to provide a smooth/flat shingle install. I wanted so much to tell the guy how stupid I felt sitting there installing shingles on this flat roof. How ludicruos the entire event was. In the following years, as a contractor, I rellished in replacing those roofs w/BUR or APP.......>>>

No matter what our opinions . What is the strongest position. Judge my argument is .. I have all these professional experts with more years in the business dealing directly with this particular issue than I could possibly live or everyone , anyone on the jury ....Judge my argument ..........the manufacture who stands behind the product preforms thousands of hours static ( sitting on a board under bright lights and sprinkler systems ) testing and guarantees the performance. People of the jury you decide. Thank you for allowing me my arguments. Another reason I'm on the fence in this once great profession>>>

I'm going to start reccommending three layers of #15.....It's gotta be an improvement over two!>>>

Ridiculing the concept was not my intention, understanding it is. That and pointing out that GAF could not give, what I believe, a valid explanation for two ply underlayment.>>>

I understand, as well as agree with you Jed.....

This is a prime example of "thinking" ourselves stupid....."Perception is reality", etc....

>>>

"asphalt shingle roof assemblies between, pitches less than 4/12 to 2/12 were allowed, provided the shingles were installed "double-coverage"." Ever do something so naturally, you can't even remember to mention it?? You're right Tom. 3-1/2 to 4" exposure for shingles. I did one with Elks at 4". No ponding.No leaks. Still there. 4" to 6" laps.

My brother and I took awater hose to one. A directed spray at a 1/2" lap could let some water in. It then trickled, unobstructed, from the 1/8" gap created by the lap, straight onto the roof, on the back of the underlying shingle. The only way we could make it leak was a hard stream directed up the roof at the joints. The roof has sat under 14" of snow and ice for days.

Thanks for mentioning which double layer was called for Tom.

Ciak. How many of the blown off roofs had wood decks? I haven't seen any in the news pictures of hurricane damage. APA tests show OSB have about 1/4 the holding power of wood. I repaired one Thursday with blown off shingles. House 8 years old. Some nails were still there and I could almost pull them with my fingers. (OSB)>>>