Underlayment Question

72chevy4x4

I have a question about felt and some of the new underlayment products. I've always used 15lb felt w/ an I&W product at the eaves. My local supply house doesn't sell I&W, but Henry's Eavesgaurd. I actually have to go to a box store to get Grace's product. So, the question's are:

1. how does Eavesgaurd compare to I&W?
2. what is the 'stated' purpose of roofing felt?
3. what are options to 15lb/30lb felt?

The reason for question #2-when I'm putting felt down, I often use a hammer stapler, but will sometimes tear the felt (such as when hitting a seam in the sheating). I've never considered felt to be a second layer of defense against water penetrating the shingle-with as many nail holes as there are, it doesn't seem water tight.

Now w/ 30lb felt at $28/roll, is a new synthetic option getting closer in cost? what about performance issues-slippery when wet? expanding or shrinking?

redzthredz

I just finished papering a 2500 sq. ft. roof with a 6 /12 pitch. ( My own home ). I did start rolling out 15# felt, but the paper does not have any tack to it and as a result can be slippery as all get out on a steeper slope roof. I live in Lakewood, Ca which is So. Cal. and the city calls for 1 layer of 15#. My opinion is go with with the 30# on a steep slope, your bones and head will thank you. You did not mention your roof pitch, so this may not apply to you.

Red

punkisntdead

certainteed has an underlayment called "roofer's select" thats supposed to resist tearing, its fiberglass reinforced. its also supposed to be a lot more resistant to wrinkling and be easier to walk on. in the hampton roads area its around $40 bucks a roll as opposed to $30 a roll for traditional 30lb. the basic purpose of felt is to temporarily dry in the roof between tear off and installation. it also helped to be a barrier between old pine sheathing boards because the resin in the boards broke down the asphalt in the shingles faster. plus its a kind of back-up in case of a hard wind driven rain.

mattp

Also Roofer's Select comes in 4sq rolls as 30lb is 2sq. I have made the switch from Select to synthetic. Synthetic comes in 10sq at 120 a roll

Renegade

God, yet another thread on underlayments and i/w
Go back and read the myriad of other heated arguments on the subject.
As far as felt. Once the roof is installed, it's main purpose is as a barrier between the dry wood deck (whatever it may be) and the moist asphalt shingles. That is it.

Too many roofers nowadays use ice and water as an excuse for lower quality work. As far as I'm concerned, I could put newspaper under there and my roof will be just fine and the owners will never have a problem with it.

Now here we go with the "ice/water is absolutely necessary" crowd.

Krakkerjak

Well said Renegade.

punkisntdead

i agree that if your work is done correctly you shouldn't have to worry about what's underneath, but what's your opinion on using i/w on the eaves to prevent leaking from ice dams? if the ice/water backs up and sits on the eave, what's going to hold the water out? shingles aren't designed for puddling water. i/w is watertight and is required to offer surestart plus warranties with certainteed.

RooferJim

I will say it once again. a shingled roof system is only designed to shed water it is not an impermeable barrier as is many flat roofing systems. hence to reason underlayments are code and manufac specs. Yes It does not make an excuse for poor flashing details or roofing practice, but only a fool would downplay common sence and time tested roofing basics.

RooferJim
www.jbennetteroofing.com

Slyfox

I have a job scheduled for re-roofing in 3 weeks, it's an insurance damage job.
I installed the esisting roof 15 yrs ago this november,
it's a 6/12 pitch, 25 yr OC 3-tabs, pot vents, #30 felt.

When I did the estimate I included the upgrade of ridge vents and ice guard, which 15 yrs ago we used neither material.

They could/would not be sold on either of these products after seeing thier original roof last 15 yr's problem free with out them.

Not every shingle roof installed with out ridge vent an i&w will fail.
Not every shingle roof installed with them will last.

__________________

Renegade

Punk, yes the proper usage for ice/water is eaves and valleys and, yes jim I am all for proper underlayment on any system. My issue starts with all these ppl that say " oh yes, you can put that system on that roof, all you have to do is run solid ice/water so it won't leak....

IF IT'S GOING TO LEAK, YOU ARE PUTTING THE WRONG SYSTEM ON THE ROOF. The ice/water is just covering up the contractors ignorance of proper systems for the particular job, or they are just making the owner spend unnecessary money.
Provided shingles are a proper system for the roof, yes, I recommend ice/water at the eaves and in the valley according to manuf specs. Then either 30# felt or 2-ply 15# in the field. That is all you need. (actually one layer of 15# is acceptable, I just prefer not to do that)

72chevy4x4

back to one of my questions, why 30# versus 15#? If choosing between 1 layer of 30# or 2 layers of 15#, wouldn't the 30# be better? This assumes it's not a low slope application.

mattp

Do a search on felt and it will answer all your questions

RooferJim

I think it depends on what your installing. On residential ashphalt shingle jobs we typicly will use certainteed Roofers Select or somtimes GAF Shingle Mate.
If it is Cedar or Slate always # 30 felt or somtimes full I&W is spec. I agree that some mistakenly believe that I&W has a mysterious magical quality and lets them get away with not following good roofing practice .