Felt Underlayment
#1
03-16-04, 10:20 PM
Felt Underlayment
Hi there--
I have had four estimates for a re-roofing job that I need to have done, and I am going to hire a contractor tomorrow. I am wondering why all of the estimates would recommend a 15lb. roofing felt instead of a 30lb. Does it add that much in cost, or is it just because it is heavier to work with?
It makes sense to me that the heavier the better. I am having a tear down and complete re-roofing done, and I live in the Pacific Northwest (read: Rains 6 months per year!). Why wouldn't I want as much vapor barrier as possible?
Thanks everyone--Don
I have had four estimates for a re-roofing job that I need to have done, and I am going to hire a contractor tomorrow. I am wondering why all of the estimates would recommend a 15lb. roofing felt instead of a 30lb. Does it add that much in cost, or is it just because it is heavier to work with?
It makes sense to me that the heavier the better. I am having a tear down and complete re-roofing done, and I live in the Pacific Northwest (read: Rains 6 months per year!). Why wouldn't I want as much vapor barrier as possible?
Thanks everyone--Don
#2
03-16-04, 10:26 PM
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You can get estimates of 30-lb felt just to see the difference there. The material will cost more, but the labor will be the same.
I always use 30 lb, just in case shingles ever blow off.
Manufacturers generally only require 15 lb for warranty, and it is a little easier to work with, but I would go with the 30.
Good Luck!
Mike
I always use 30 lb, just in case shingles ever blow off.
Manufacturers generally only require 15 lb for warranty, and it is a little easier to work with, but I would go with the 30.
Good Luck!
Mike
#4
03-17-04, 01:36 PM
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Hey, Mojo!
Nope. A little early for them, and they'll be on the other end of the Albemarle or more likely in the Pamlico Sound when they do. Usually too much fresh water here on the western end of the Albemarle to get much more than fresh water fish and stripped bass (rock) most of the time.
Mike
Nope. A little early for them, and they'll be on the other end of the Albemarle or more likely in the Pamlico Sound when they do. Usually too much fresh water here on the western end of the Albemarle to get much more than fresh water fish and stripped bass (rock) most of the time.
Mike
#5
03-19-04, 06:18 AM
I always use 30# felt. Of course I live and work in a ski area with lots of snow. It's a little harder to install flat and nice and is a 2 sq roll as opposed to 4 sq for 15#.
Jim
Jim
#7
03-28-04, 05:12 PM
Roofing underlayment
Dear friends
As a new member this is the first post I am placing. Reading the post under roof underlayment I can see that some of you want to use #15 and some others #30 nailed or stapled to the plywood or OSB (in old houses wood boards). Did any one know the reason why we use underlayment before the roof shingles??? Do we use it because it is customary years after years to be used, or it is imperative to be used because serve perhaps for very important purpose??????
Drawings, distribuitors and Building Inspectors always requiring minimum of #15 felt in the roof and #30 in the valleys.
Do you ever ask these people WHY the felt is needed??????
Ask next time the Building Inspector, the answer will be "Because the Building Code say so". Remember you want from him a specific answer WHY the felt is needed and it purpose.
He probably wouldn't know the answer or if he give you one will be only a guess.
I will like to hear your opinion so I can compare your thought.
Next time I will answer to this confusing contoversy.
almark
As a new member this is the first post I am placing. Reading the post under roof underlayment I can see that some of you want to use #15 and some others #30 nailed or stapled to the plywood or OSB (in old houses wood boards). Did any one know the reason why we use underlayment before the roof shingles??? Do we use it because it is customary years after years to be used, or it is imperative to be used because serve perhaps for very important purpose??????
Drawings, distribuitors and Building Inspectors always requiring minimum of #15 felt in the roof and #30 in the valleys.
Do you ever ask these people WHY the felt is needed??????
Ask next time the Building Inspector, the answer will be "Because the Building Code say so". Remember you want from him a specific answer WHY the felt is needed and it purpose.
He probably wouldn't know the answer or if he give you one will be only a guess.
I will like to hear your opinion so I can compare your thought.
Next time I will answer to this confusing contoversy.
almark
#8
03-28-04, 05:44 PM
The felt is needed because that is what dry's the roof in. With out it, everytime it rains your going to be buying more buckets and replacing your walls and ceilings. It serves as a vapor barrier as well.
Dan #15 is sufficient, but if you want #30 tell your roofing contractor that, that is what you want. Yes it's heavier, and it might last longer, but it's going to do the same job as the #125felt.
Dan #15 is sufficient, but if you want #30 tell your roofing contractor that, that is what you want. Yes it's heavier, and it might last longer, but it's going to do the same job as the #125felt.
#9
03-29-04, 08:14 PM
Originally posted by boardslinger
The felt is needed because that is what dry's the roof in. With out it, everytime it rains your going to be buying more buckets and replacing your walls and ceilings. It serves as a vapor barrier as well.
Dan #15 is sufficient, but if you want #30 tell your roofing contractor that, that is what you want. Yes it's heavier, and it might last longer, but it's going to do the same job as the #125felt.
The felt is needed because that is what dry's the roof in. With out it, everytime it rains your going to be buying more buckets and replacing your walls and ceilings. It serves as a vapor barrier as well.
Dan #15 is sufficient, but if you want #30 tell your roofing contractor that, that is what you want. Yes it's heavier, and it might last longer, but it's going to do the same job as the #125felt.
Dear Boardslinger
There are hundreds of controversies regarding the use of underlayment on the roof. What you say "The felt is needed because that is what dry's the roof in" , sorry but I desagree with you and thousand more. "Everytime it rains your going to be buying more buckets and replacing your walls and ceilings".
If you talking having an old leaking roofing shingles, I agree with you, but the underlayment have nothing to do keeping the roof dry. Do you ever figured how many perforation of staples and nails that poor underlayment have received during the roof application ???
Do you ever rip out a roof to install a new one and found moist between the underlayment and the plywood sheathing ???
so why is so important to install the underlayment???
Is NOT good for waterproof (because is punched with thousand and thousand nails) NO GOOD for vapor barrier(Because is punched with.....) So why we need the underlayment ????
Please ask the manufacturer and the Building inspector why!!!!
I will like to ear from you members what they have to say, then I will post the pros and the contras of the underlayment.
For now I can tell you that the only reason the underlayment is placed on the roof is to keep the sheathing dry before the shingle installation.
Belive me I honestly respect all your thoughts.
Almark
#10
03-29-04, 08:25 PM
Didn't mean to get your feathers ruffled alan. The reason I say what I said, is I started out in the trades as a roofer. Try to roof a house without felt down, and see how much water gets in. It's purpose is to divert the water away from the joints of the wood sheeting. And you will still have 1000's of holes wether the felt is laid or not. This is not to be taken as agressive, but I urge you to roof a house that has no felt. You will see why the felt is needed. I for one can say that I have seen the damage of not having felt under roofing.
#11
05-18-04, 07:36 PM
Reroofing
Dear Boardslinger
Besides the disagreement the use of underlayment on the roof, I like to ask you a question since you are a professional roofer. Maybe I have the answer already, but I like if it is possible you to answered.
Couple weeks ago, I inspected a gable roof that a contractor re roofed with dimensional fiberglass shingles. The house is located in a beautiful country side. Approaching the house with my jeep, the re roof appears acceptable, however, when I started the inspection, my thoughts changed.
The aluminum fascia was nailed with common nails(finished nails) already sign of rust, so many nails that the fascia was all warped. This is obvious wrong, flashing around the chimney was nailed above the shingles, nails are exposed, the edge on the rake sides was cut uneven (1" to 3"), the staggering of the shingles instead be 5 1/2" next 15 1/2" and next 5 1/2" again, are all different sizes. My MAIN QUESTION is: The roof like I said is Gable type structure, they never cut back the old roof (the first one) never installed the starting course and drip edges. So when luck the fascia side, you can see the two roofs. I understand that after the gutters installation wouldn’t be noted, but is this right ? after 40 years this is the first time I see something like this. In my opinion this is done by an amateur. What do you think ?...
Please respond me. thank you
almark
Besides the disagreement the use of underlayment on the roof, I like to ask you a question since you are a professional roofer. Maybe I have the answer already, but I like if it is possible you to answered.
Couple weeks ago, I inspected a gable roof that a contractor re roofed with dimensional fiberglass shingles. The house is located in a beautiful country side. Approaching the house with my jeep, the re roof appears acceptable, however, when I started the inspection, my thoughts changed.
The aluminum fascia was nailed with common nails(finished nails) already sign of rust, so many nails that the fascia was all warped. This is obvious wrong, flashing around the chimney was nailed above the shingles, nails are exposed, the edge on the rake sides was cut uneven (1" to 3"), the staggering of the shingles instead be 5 1/2" next 15 1/2" and next 5 1/2" again, are all different sizes. My MAIN QUESTION is: The roof like I said is Gable type structure, they never cut back the old roof (the first one) never installed the starting course and drip edges. So when luck the fascia side, you can see the two roofs. I understand that after the gutters installation wouldn’t be noted, but is this right ? after 40 years this is the first time I see something like this. In my opinion this is done by an amateur. What do you think ?...
Please respond me. thank you
almark
#12
05-18-04, 08:22 PM
The aluminum fascia was nailed with common nails(finished nails) already sign of rust, so many nails that the fascia was all warped. This is obvious wrong, flashing around the chimney was nailed above the shingles, nails are exposed, the edge on the rake sides was cut uneven (1" to 3"), the staggering of the shingles instead be 5 1/2" next 15 1/2" and next 5 1/2" again, are all different sizes.
#13
05-19-04, 11:35 AM
this is the first time I see something like this. In my opinion this is done by an amateur. What do you think ?...
ED
#14
05-19-04, 03:04 PM
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Felt is needed for a few different reasons.
1 - to "dry the roof in" until the shingles can be applied.
Once the shingles are applied, the felt doesn't really help shed water as much. (as noted the gazillion nail holes in it) However, it will help ever so slightly. "Some is better than none."
2 - to separate the shingles from "new" plywood. New plywood has oils and resins that can possibly adversely affect the shingles.
3 - to separate the shingles from the decking to allow for any deck movement.
Every deck on every house has movement. If the shingles are able to seal directly to the deck....and the deck moves....the shingles could possibly fracture. At the very least, the shingle is under more stress.
Felt will serve as a separating sheet to take the stress for any deck movement.
There is nothing wrong with the #15 felt. It is common practice. They are not trying to "rip you off". Some roofers believe that #30 is just the way to go. Neither are wrong. It's more personal preference.
Most, if not all manufacturers, only require #15.
BIG QUESTION:
What kind of shingle will you be using?
If you are installing a 3-tab shingle, you will need to go with #15 felt.
3-tab shingles are typically not heavy enough to weigh down any imperfections in the #30 felt...like wrinkles or waves. Any felt imperfections will "telegraph" right through and you will notice it even after the 3-tabs are installed.
If you are using a dimensional shingle, either felt will be just fine.
Good luck.
1 - to "dry the roof in" until the shingles can be applied.
Once the shingles are applied, the felt doesn't really help shed water as much. (as noted the gazillion nail holes in it) However, it will help ever so slightly. "Some is better than none."
2 - to separate the shingles from "new" plywood. New plywood has oils and resins that can possibly adversely affect the shingles.
3 - to separate the shingles from the decking to allow for any deck movement.
Every deck on every house has movement. If the shingles are able to seal directly to the deck....and the deck moves....the shingles could possibly fracture. At the very least, the shingle is under more stress.
Felt will serve as a separating sheet to take the stress for any deck movement.
There is nothing wrong with the #15 felt. It is common practice. They are not trying to "rip you off". Some roofers believe that #30 is just the way to go. Neither are wrong. It's more personal preference.
Most, if not all manufacturers, only require #15.
BIG QUESTION:
What kind of shingle will you be using?
If you are installing a 3-tab shingle, you will need to go with #15 felt.
3-tab shingles are typically not heavy enough to weigh down any imperfections in the #30 felt...like wrinkles or waves. Any felt imperfections will "telegraph" right through and you will notice it even after the 3-tabs are installed.
If you are using a dimensional shingle, either felt will be just fine.
Good luck.
#16
05-27-04, 02:07 PM
Tar Paper
It is true that tar paper, when used as underlayment, get perforated by the nails holding the shingles. However, For the water to work its way past the shingles and the paper, there needs to be a little pressure. Otherwise, water running onto the tar paper just runs down the slope (that's easier than working its way around the nail). So, in practice, tar paper does help keep the water working past the shingles away from the roof interior (but only up to a point).
15# paper is very easy to tear, and when workmen are on the roof, walking on the tar paper, tears happen often. Water running down a papered slope that encounters a tear now has an easy entry to the roof deck. 30# paper tears less easily, and is therefore better.
If water has a good chance of getting behind the shingles (think ice-dams), then the appropriate underlayment is Ice and Water Shield membrane. In theory, the material is much thicker than paper and acts as a gasket around the nail. In practice, the membrane must not be stretched, otherwise it does not work well as a "gasket". As well, the membrane needs to adhere properly to the deck, and be properly overlapped to avoid possible entry points for water.
We don't use tar paper any more as the material is easily damaged. Our preference is a polypropylene sheet known as Triflex-30. We're very pleased with its performance (especially when a storm comes up when the roof is open!).
15# paper is very easy to tear, and when workmen are on the roof, walking on the tar paper, tears happen often. Water running down a papered slope that encounters a tear now has an easy entry to the roof deck. 30# paper tears less easily, and is therefore better.
If water has a good chance of getting behind the shingles (think ice-dams), then the appropriate underlayment is Ice and Water Shield membrane. In theory, the material is much thicker than paper and acts as a gasket around the nail. In practice, the membrane must not be stretched, otherwise it does not work well as a "gasket". As well, the membrane needs to adhere properly to the deck, and be properly overlapped to avoid possible entry points for water.
We don't use tar paper any more as the material is easily damaged. Our preference is a polypropylene sheet known as Triflex-30. We're very pleased with its performance (especially when a storm comes up when the roof is open!).
