What is Tar Paper for?

[Guest]

Ok folks, answer this one. Most asphalt roofing manufacturers request a felt paper underlayment under their shingles. What does the felt paper do? I mean besides void the warranty if you do not use the felt paper. Does it buffer the shingles from the wood to keep the wood from sucking the life out of the shingles? If this is the case, does 30lb. felt work better than 15 lb. felt? Does the cheap stuff they sell in the big Box stores for the self doer's void the shingle warranty? Lets hear some good solid reasons for the tar paper.
Warren

[Guest]

Re: What is Tar Paper for?

1. It provides a secondary weather barrier.

2. For basic asphalt shingles, opt for the 15# felt.

[Guest]

Re: What is Tar Paper for?

It provides a quick weatherproofing during construction. The shingles can be postponed until the carpenters make up their mind how they are going to finish the cornice.

Secondary moisture barrier. Very important.

Helps grip the nails for a tighter seal, probably not that important.

We specify #30 and lap it 6 inches. If we have to use #15, we lap it half way giving a double layer.

#30 (No. 30) felt is closer to the thickness of the felt originally manufactured as 15# (15 pound).

#30 is easier to cut and tuck in tight places such as cornice returns.

glenn

[Guest]

Re: What is Tar Paper for?

I am not comfortable buying the secondary moisture barrier theory. Each shingle we put on has atleast 4 nails that poke a hole through the paper. This does not include the plastic cap nails & or staples to hold the paper to the deck. If I am counting on the tar paper to be a secondary barrier, then I am not doing my primary job (installing shingles) properly. As for griping the nails tighter... I would say you would be better off to go with a thicker roof deck. As for the carpenters making up their mind how to finish the cornice... Isn't that what the designers & architectural type people get the big bucks for? Figuring the cornice out before the job starts. I will buy the temporary moisture barrier until you can put on all the shingles. After we put the shingles on we don't want the felt paper to see water again until possibly we reroof in 25 years for you see, we plan to still be in business when the shingles wear out. We also plan on being called back because we did the job correctly the first time around & are honest & fair with our customers.

[Guest]

Re: What is Tar Paper for?

It's my understanding that the purpose of the paper is to provide a shear layer between plywood and the asphalt shingles. As the shingles expand and contract on a roof they would normally tear some because the substrate won't move. The paper allows for movement.

[Guest]

Re: What is Tar Paper for?

What about the shingles "sweating" and rotting out the roof sheathing?

[Guest]

Re: What is Tar Paper for?

Oh Dick,
You sure are a jolly joker. I suppose my 40 year IKO shingles sweat alot because they weigh alot. You are really cracking me up.
And Glen,¿the tar paper grips the nails for a tighter seal" I guess this sight should be called comedy showcase.
Warren,
Good question. I am sure your looking for a good answer. So far Mike Nathan makes the most sense, although I would say that is probably more opinion than fact. Still it isn't a bad theory. I wish I had a good answer for you but alass I only have an opinion. I like the theory that the paper stops roof deck from drawing some of the life out of the shingles. Heat destroys oil (ie tar in the shingles) over a period of time. The heat from the attic transfering through the roof deck would in therory help to breakdown the shingles. On top of that if the shingles stick to the plywood roof deck & the deck comes & goes you have another potential for a failure.(Mike Nathans theory)
Good luck. The trade needs more thinkers like you & less jokers.

[Guest]

Re: What is Tar Paper for?

How's this for a joke: Your warranty is no good because you didn't follow the manufacturer's installation instructions? And while we're at it, Glenn's recommendation for 30# over 15# is a good idea because the more asphalt in the paper, the more seal around those troublesome nail penetrations.

[Guest]

Re: What is Tar Paper for?

Dick,
I don't know about S-Sam but the last 3 job's we did we used 30 lb. felt. All of the jobs we do we use atleast 15 lb. felt (& not the cheap stuff). As a side note in the 28 years I have been in the trade (my father was in it long before that) We have had about 4 warranty claims. The field rep came out & looked at each job. They were all good enough for the field rep to pay our claim. Now, all I was asking for (if you can read the 1st question) is what purpose does it serve. No one said on this post that they didn't use it yet. I am just looking for a GOOD answer. That is ALL.
Warren

[Guest]

Re: What is Tar Paper for?

I was told that before the invention of plywood when they used 3/4" x12" pine boards ,that the sap from the pine would eat through the asphalt shingles.So tar paper was used to protect the shingles.I like the fact that you can have quick protection once you strip the old shingles by applying a layer or tar paper. Tim

[Guest]

Re: What is Tar Paper for?

S-Sam,

What is your experience? Your remarks are flippant to say the least. Please provide evidence that what you say is the end all and be all becausse the people you insult are ones I've come to respect.

Thanks.

John

[Guest]

Re: What is Tar Paper for?

Warren,
Thicker sheathing won't help grip the nail for a tighter seal. I donbt the felt is all that much help either, but many count on #30 felt for being somewhat self sealing around peneterations in comparison to, say, Tyvek.

Having a secondary barrier doesn't cast dispersions on the quality of the primary barrier. Its a low costs safety net.

The fact is that it is required. It is inexpensive and has more advantages that disadvantges. As such, trying to decide where it is really needed or not and working to have the requirement remove, has very little priority on my calendar.

You ask for reasons for using felt. I gave you all I know.

S-Sam,

Actually, there is evidence that felt may actually shorten the life of shingles, although probably an insignificant amount. But if you "like the idea" that it increases the life of the shingles, that's OK. I happy that you felt entertained.

I cannot think of any reason why anyone would want to leave the tarpaper off a roof or spend a lot of time trying to evaluate it. There are a lot of bigger problems.

glenn

[Guest]

Re: What is Tar Paper for?

Gee, I thought it was a good question, myownself.

Since I rarely use anything but metal roofing (exception would be the occasional remodel with a comp roof), I can't speak to the issue of the shingle Mfr. specing felt underlay.

I always paper my roof decking immediately for the sole purpose of keeping the rain off the decking and out of the house. #30 felt is a most acceptable temporary roof and will serve for many weeks when Momma Nature is in one of her snits and real roofing ain't gonna happen.

The temporary roofing allows time for the painter to spray the facia without painting the real roofing, and I frequently have gable ends above roofing that are to receive rock or stucco and there is no known (to me) way to adequately protect metal roofing against damage by the rock man.

And black felt is a rather inexpensive temporary solution (I haven't used #15 felt since long ago when it changed from being "15 pound" material to "#15" material. Some of that stuff you could see through on a bright day). Should the winds of March remove some, or the rock man tear it up more than somewhat, I just re-roof a little.

Don't know how I'd get along without it.

S-Sam:
You need to get back on your meds, son. We have some snippy fights around here now and again, but most of these guys make a serious effort to trade useful information.

My opinion; worth price charged.
CX

[Guest]

Re: What is Tar Paper for?

Glen,
I was in no way trying to get the requirement removed. I was not trying to debate or dispute an unnessary subject. What I was trying to do is increase my knowledge of why we do the things we do. I have always believed that it was inexpensive temporary protection untill the roofing was installed. I was however curious as to why it would void a shingle manufacturers warranty. As you can see, we still do not have that answer. I like to do things that make good common sense & have a good reason for doing things the way we do them. I was looking for the usefull information that Kelly said can be found on this site.
S-Sam, You may not have given to much usefull information to the question but you sure made me smile. No one else gives their credentials. I think you just hit a nerve. I'll bet you have some amusing comments on the job site. As far as the tar paper goes, even the factory rep's have been unable to supply a good reason. You all have a good week, & thank you all for your responses.

[Guest]

Re: What is Tar Paper for?

Warren:

Have you posed your question on any of the shingle manufacturer's web sites? I assume there are some. Or perhaps there is a roofing forum out there somewhere.

In all other applications for roofing felt that I'm aware of (mainly exterior walls behind sidings or masonary veneers), it's used as a moisture barrier, and such is stated in the specs.

Maybe the shingle mfrs are using it to cover their legal posteriors, rather than for protection of their product.

CX