What's the function of felt underlay for shingles?

Shingles (standard three tab type) have felt (tar paper?) installed on the roof first, and then the shingles are installed. What is the function of the felt? I understand there are 2 types of felt, perforated and non-perforated. Is perforated felt for vapour movement? What happens if the felt is not installed?
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wrote:

There is some foam stuff they use under the steel to lower the noise. I did not install it because I did not even know it existed when I put on my steel about 10 years ago. Besides that, there is an attic in between. On my barn and garage, it rain is a little noisy, but who cares in those buildings. Hail on the other hand is annoying, but for those couple hail storms each year, who cares.

That's their own fault for dying <lol>
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On Sun, 3 Apr 2011 05:43:53 -0700 (PDT), " snipped-for-privacy@optonline.net"

Your replacement shingle roof will not last nearly as long as your current roof. You can count on it. Sinse the asbestos fiber has been eliminated, and asphalt content reduced, even the high end "asphalt" shingles have become extremely dissapointing in the lifespan department. The socalled "fiberglass" shingles in particular.

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On Apr 3, 3:31 pm, snipped-for-privacy@snyder.on.ca wrote:

Please list the number of assumptions you made to come up with that assertion. I stopped counting after three.

Asbestos is a silicate mineral fiber, just like fiberglass. The substitution of one for another has nothing to do with the longevity of a shingle. The longevity is affected by other factors.
Over the years I've installed shingles that run the gamut from lowest end three-tab to 50 year architectural, and have found that you pretty much get what you pay for. Rated shingles are going to provide right around the listed effective life. If they're in an extreme climate, the lifespan will be shortened a bit, but it won't be a 50% reduction.
R
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On Sun, 3 Apr 2011 20:14:09 -0700 (PDT), RicodJour

Good to know the "40 year" year shingles I had done 8 about years ago will outlive me. Wait.... Looks like the ridge shingles curled up a bit at the lips. Hope that doesn't get worse.
--Vic
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40 year shingles are usually too thick/stiff to bend over a ridge unless it's a really shallow sloped roof, and most manufacturer's don't make a cap shingle that will match the 40-year rating, so installers use a lower grade shingle for the cap. If that was what was done on your house, you probably wouldn't notice it from the ground, but you won't be getting the full life from the ridge cap. Do you happen to know what was used for the ridge cap shingles?
R
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On Sun, 3 Apr 2011 20:57:34 -0700 (PDT), RicodJour

Sorry, can't remember the manufacturer, except it was a major. Funny thing is I googled shingle manufacturers and none clang a bell. Any big one recently go out of business or change names? If not they're probably Owens-Corning. The ridge shingles seem to match the others, as I recall 40-year architectural, but only sure about the 40-year part. They look to be at least 4 times thicker than the stuff I had torn off and give the roof a look of "depth" The roofer showed me samples and recommended a 30-year. When I went for the thicker stuff he seemed unhappy enough about that so's I had to push him a little. Said he'd have to charge a couple/few hundred more on the labor besides the extra cost of the shingle. Understandable. I did chicken-ladder roll roofing on my ma's steep roof when I was younger and remember carrying those rolls up a 30-footer, so weight is a factor. Might be something else that makes them harder to install too, don't know. Never figured why he was resistant except maybe it would rankle his crew leader or somebody on the crew was hurting. They did a good job and I got the shingles I wanted. They look real good. I've been on the roof a few times and didn't notice the ridges being different than the others up close. House is a bungalow with not much roof slope. I'd say the bends are about 30 degrees. Wife pointed out the curls to me. The curls weren't there a couple years ago, last time I was on the roof. I would have noticed. You have to be the right distance from the house on the ground to notice. Thought briefly about calling the roofer out. He's a local business. Or was, don't know if he's still operating. Not too concerned, but a bit surprised. Doesn't appear to be more than a mild cosmetic flaw if it doesn't get worse. I did some woodwork recently that has a similar issue (-: I'll get up there in a week or two and take a closer look.
--Vic
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Post back what you find. A picture or two would be dandy. I've never seen cap shingles curl like that. On the down side, you might have to replace them sooner than the rest, on the up side, those are by far the easiest shingles to replace, and also straddling the ridge makes most people feel safer.
R
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On Sun, 3 Apr 2011 20:14:09 -0700 (PDT), RicodJour

No assumptions. Experience

Well, I put 25 year architectural shingles on my house and they required replacement in 17 years. The original 3 tab "contractor" shingles lasted about 16. The house is 38 years old. I put 25 year 3 tabs on about 5 years ago, figuring I might not need to change them again in my tenure here - the wife wants a bungalow in the next ten years. In years past, (late sixties early seventies)I've installed shingles that lasted 25 years or more - and they were not premium shingles. The contractor that did my last roof said he has been very upset with the lifespan of the mid eighties and later materials and would not even quote me on less than the 25 year shingle, because he won't install them.
The weather here is not what I would call "extreme" but we do get wide temperature variations (from about -10F to 95F) and a fair amount of snow some years - with lots of freeze thaw cycles

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On Apr 4, 12:24 am, snipped-for-privacy@snyder.on.ca wrote:

I think what you're seeing is the increased and improved testing of shingles showing up. Improved being a manufacturer's term. If you've ever noticed that things are generally failing closer to their rated life, that's because of improved testing and engineering. We never had so many choices of shingle longevity, and types, as we do now, but shingles are like house paint as far as I am concerned. Buy the best materials you can afford/justify as the bulk of the work is in the installation/preparation, and the down side of shortened life is usually delayed maintenance leading to far bigger problems.
On your particular roof - that's a fairly big swing in temperature, but not the most extreme, so I'm curious why you're getting so much shorter life. Has your roof been stripped to the sheathing each time, or have they been roofing over the old?
R
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On Mon, 4 Apr 2011 09:00:48 -0700 (PDT), RicodJour

replacement has been necessary. As I said - I replace before I end up with a leak. When bare "fiber" shows, with no grit left ANYWHERE on the roof, the roof comes off.. If shingles curl and lift I'll fix a few, but if it becomes a common issue, it comes off.
On my daughter's place she had leaks and ice-dam backup, so we had the roof replaced and immediately re-insulated the attic (added about 3X what was there). No ice dams this year.. Put on double width ice guard, and ice guard up the edges of the gable end as well as along where her roof joins the neighbour's roof (end unit town house).
It's six levels high, so no way I was going up on that one!!!
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