Is it important to have roofing underlayment (tar paper) to be placed either vertical or horizontal or does it matter which in which direction applied?
One roofer placed a portion vertical & another horizontal though on different roof sections. Considering water will flow downward, it seems like the material placed horizontal would repel water better. Roof is 9/12.
Appreciate your advise!
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Replies
I carefully line up and install the underlayment parallel to the ridge and eave line. The lines on the felt help me line up the shingles
You are never going to get any agreement on this (I predict). People even argue about whether the tar paper is necessary, for example, "How much protection does it offer when a zillion roofing nails go through it?"
>> People even argue about whether the tar paper is necessary, for example, << Not around here we don't. Tarpaper serves a few purposes: 1) as a secondary water barrier, although as you say, once it gets million holes it's usefulness is questionable and 2) as a temporary roof before/while the new shingles are applied. This is more for new construction where the roof may sit a month or more before being shingled - and therefore would generally not be as important in a re-roof situation since many/most roofing companies will have the new roof on within a day or so. 3) it keeps the oils, etc in the asphalt shingles from being absorbed into the wood roof deck. If you remove a asphalt shingle roof that was installed without tar paper and it is in a hot location, often the shingles will be melted into the wood of the roof sheathing. This reduces the life of the asphalt shingles. This last item is one that less informed folks are not aware of.
OK - now someone will argue with me... :-)
BTW - the guy who installed the paper vertically musta been smokin' somethin'. For those who find it all so complicated, most shingle packages have fairly easy to follow instructions complete with pictures!
Edited 9/19/2005 7:27 pm ET by Matt
"Not around here they don't?" Sure they do -- there have been bitter disputes on BT as to whether tarpaper is essential.
I accept that it is, because all you pros say so, and so do the roofing books. BUT -- I was stripping some shingles that had been on a 12/12 pitch for about 20 years. No tar paper, because when my hippie brothers-in-law helped me shingle the roof originally, they thought tarpaper was unnecessary, and I went along. The plywood under the shingles was like new, despite the lack of tarpaper. No sign of weather, no sign of infiltration of hydrocarbons from the shingles. Maybe this was just the luck of the ignorant?
(I was stripping the shingles not because there was anything wrong with them, but so that I could frame in the roof of an addition. I used ice and water shield on the addition, not tarpaper, because the shingle package said to, for a low pitch roof, 3.6 in 12.)
Being only a homeowner and not a builder, I have no idea what is Ice & Water Shield? We used tar paper perhaps because Ice is generally not existant on roofs for more than a day or so.
Apparently this subject is simply how one prefers to do & with each having its own reasons.
Many thanks for the input though!
Interesting... where do you live? What was the exposure of the roof slope in question?
It's our cabin on Vinalhaven, ME (island in Penobscot Bay). The exposure is to the east. The pitch is 3.6/12, and the shingle wrapper (and many roofing books/websites) says you need to cover the entire roof with ice and water shield when shingling with pitch < 4/12. Probably overkill, but better safe than sorry. The membrane is a real trip to put on -- if the sun hits it you have an incredibly gooey sticky mess on your hands (and your face, and the roof deck and your butt and everywhere else!).
People may get tied up in knots over particular details (like drip edge and shingle overlap, for instance), but the key to remember is that a roof covering is more of a system rather than an individual piece. The system has may components that work together, such as:
Straight, level, and square top plate for the rafters.
Straight, square, and same pitched rafters for your sheathing.
Properly spaced sheathing that gives a flat surface for your coverings.
Last ditch waterproof coverings in case you primary covering fails.
Water guidence systems like drip edges and valley flashing to take over where the primary covering ends.
Primary covering accessories - like the ridge cap, the stack boots, the starter row of shingles at the bottom of the eaves.
Primary covering.
The system works best when all the components are in place... but it will still work even with compromised components, because other things are there to help compensate.Rebuilding my home in Cypress, CA
Also a CRX fanatic!
Where on the Island are you?
I was just out this last weekend and did two slate jobs and a chimney.
What a marvelous piece of Maine that "rock" is.
I've got to go out in a couple of weeks to put copper gutter on a place on the Pleasant River.
We are on Calderwood Neck. I haven't seen too many slate roofs on the island -- they are probably on the houses of quality folk, hidden away from the stares of the vulgar.
I conducted an experiment on my house 22 years ago. One section of the house had felt paper and another section with identical exposure had none. I am reroofing the house now (No leaks but some curling shingles and I want to do this before too many years pass and I can't do it.) and I can see no appreciable difference.
I would always use I&W and felt paper on a customer's roof but I am not convinced it makes any difference in the finished roof.
What shingles, what pitch and what climate, if you don't mind saying?
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
Three tab 25 year, basic cheap shingle, 12 in 12 pitch, upstate NY
Reroofing with heavy laminated shingles. I&W at eaves though the first roof did not have this and had no ice dam problems.
See how everyone with no problems deleting the felt has a 12/12 pitch?In Florida, every 3/12 pitch I re-rooofed showed signs of water under shingles making water marks on the felt
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
I know that convention is parallel to the roof line and over lapping.
I also know that water is probably the weirdest substance on earth in that its properties are so difficult to control.
I stuck with convention on my roof.
Is it possible that the vertical piece of underlayment was actually Ice&Water shield running vertically down the rake? I see that quite often.
EDIT: or even I&W run vertically in the valleys? Just throwing some possibilities out there before we all go and lynch the roofer.
Edited 9/19/2005 7:25 pm ET by dieselpig
If you are trying to 'dry in' a 9/12 roof to shingle later or to beat a rain storm, it's easier to run felt vertical, we use a 'chicken ladder',and its alot faster. If you are going to paper and shingle as you go, you might as well run it horizontal.Now remember I am old and gray so a 9/12 is not a walk on for me. We also lap 4" in stead of 2' . Also in my area there is one village I know of that requires vertical felt only,they made a friend of mine tear off and redo a section of roofing when the inspector saw horiz. felt. On that slope I have had horiz. felt keep out lots of very heavy rain and see no down side to it.
Regards
Are we really having this conversation?
Unless gravity works differently in your part of the country than mine, or if the wind never blows, always horizontal. Would you run your shingles vertical? How bout tyvek ?
I think someone is puttin me on...............
I like to run mine on a diagonal.Birth, school, work, death.....................
Only to the low side of the roof .................
West of the Mississippi, (or south of the equator, of course..........
new house or re-roof?
Doesn't matter on the former, might matter on the later. Felt basically becomes an expansion joint between the sheathing and the roof covering after the roof is applied. Any roofer relying on the felt to keep the finished roof from leaking should seek employment as a drywall hanger.
Birth, school, work, death.....................
Well, you have a lot of opinions now.
Want a fact or two?
The specs for shingle underlayment read that a horizontal lap shopuld be 2" and that when a verticle lap occours, it should be 4" to 6" depending on slope pitch.
For those purists who think it is only OK to run the felt horizontally, they have to explain what they do with their lapps when they come to the end of a roll. They start a nbew roll and lapp it over the old at least 4" to 6" depending on roof pitch.
It is easier to stretch the wrinkles out of a roll on a steeper roof when you run it verticlally so it can result in a better looking roof.
now, for my opinion and practice...
on a roof pitched from 3/12 to 6/12, I always roll horizontally.
on a roof pitched 8/12 to 10/12, I roll vertically and lapp edges 6"
on a roof pitched steeper than that, I roll vertically and lapp 4"
I doubt very much that your roofer did you a dis-service in any way.
Welcome to the
Taunton University of Knowledge FHB Campus at Breaktime.
where ...
Excellence is its own reward!
"The specs for shingle underlayment read that a horizontal lap shopuld be 2"..."
Just curious what specs you're referring to. I've never seen specs on felt paper. And I don't recall reading anything about it on the shingle wrapper.
But I don't generally read instructions, so I might have missed it. (-:
When I'm feeling down, I like to whistle. It makes the neighbor's dog run to the end of his chain and gag himself.
The 2" horozontal lap is a code requirement here in NC. We use the IRC2000 but it may be something that NC added. Also, now that I looked it up, it says: "Underlayment shall be applied shingle fashon, parallel to and starting from the eaves and lapped 2"..."
It used to be in the specs for shingles.It has been a long time ago that I had the books, but each manufacturer hada spec book, looseleaf with hundreds of pages. I had JM, GAF, Celotex, and maybe others. You had to have the books to write specs into contracts or to bid on jobs that requested "According to JM #85-437" or equivalent.So I can't refer to book, chapter and verse, but I have read roofing specs so many times I probably quote some in my sleep still, more for BUR than for shingles, but this is one you can trust my word on and take it to the bank.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!