Install Architectural Shingles over 3-tab Layer-Is this ok?


#1

I’m getting quotes to install Architectural shingles. One salesman suggested I tear off the existing layer of 3-tab shingles due to the extra weight of architectural shingles. He said that weight and the weight of snow could “potentially” be a problem. Nobody else has suggested a tear-off. Is this something I should consider or is this simply a sales pitch?

Thanks, Dave


#2

There are a lot of reasons to rip the existing roof but unless there is some kind of abnormal conditions like beams 24" on center then weight shouldn’t be one of them. Maybe there are multiple layers? We always tear off the existing roof/s before a new install, we don’t do recovers.


#3

I agree with tar monkey. Weight is normally not the issue, most of the time the first roof is curlled up or is damaged to the point it will telegraph thru to the new shingles.


#4

if you cover…you dont get ice & water barrier, and your 30 year shingle will last only 17 or so years. also you dont know if you are covering rotted decking or anyhting like that. what part of the country are you located?


#5

Only have done one laminate over 3 tab and I hope it will be my last. Home owner tight on funds phone book job moving in less than 5 years deal. Dropped the tear off charge so low figured it was the way she was going.

Removed the ridge, vents and cut the overhang to be flush with the cedar and installed drip edge and ran them at a 5 5/8th in exposure. If there were any curled shingles the corners were cut back a few inches.

Tried to explain the thick and normal rows to the home owner but she was dead set on a roof over, her neighbor had one done recently.

In the past 4 years all tear offs have had laminates but on a roof over a three tab may look better. If you could find English laminate shingles and run under the original shingles it would look best.


#6

I live in the Chicago suburbs and the condition of the existing roof is good, only one layer of shingles. The house was made in 1989. We are considering GAF Timberline Ultra or Owens Corning. At the moment I’m not sure which one to choose.

Thanks for your help.

Dave


#7

i think you`ve only had one good roofer come out! definitely rip it,put in eaveflashing,ice shield,balanced ventilation system–you only want to do it once,have it last for the life of the shingles,and not have problems–as a reroof we call that LIGHTING A FUSE 1)plywood per sq.ft.is coded at 4 lb per,so it is too heavy(particularly w/a snow load and 2)typically the roof/plywood breathes thru the felt/shingles,so when the shingles may last the 17 yrs instead of 30,you usually need to replace all of the plywood because of dryrot before the shingles go bad!


#8

“if you cover…you dont get ice & water barrier, and your 30 year shingle will last only 17 or so years.”

How come the thirty year shingle will last only seventeen years?


#9

simonkenton,

That’s a good question.

marshall ext.
Why will a 30 yr shingle only last 17 or so years if installed over an existing roof? That’s half the expected lifespan.
Just curious.


#10

“2)typically the roof/plywood breathes thru the felt/shingles,so when the shingles may last the 17 yrs instead of 30,you usually need to replace all of the plywood because of dryrot before the shingles go bad!”

The roof/plywood can’t breathe through felt paper and shingles. Felt paper is a vapor barrier.
A properly built attic breathes through the ridge vent, and soffit vents.