Underlayment used under asphalt shingle roof.

My house is going to need a new roof in the spring and I am going to use architechural asphault shingle. my questions is what type of underlayment is best. I put on the existing roof years ago and at that time we used 15 pound felt, and no Ice barrier. I was checking on the underlayments being used today and some say the composite underlayment is good and some say it does not let the roof breath and rots out the sheeting or deck in a short amound of time. what is your opinion? another question is about the ice and water barrier. some say to use it over the eaves and others say to use it along the eaves but also going up and down the gable ends to the peak. which is true? it's been a while since I roofed a house and I know there have been improvements in the materials, but if these things are better or not is the question. thanks in advance for any hep you might give. I forgot to add that I am in Iowa.

lyons1046

 

I don't get on roofs, but I have heard good responses regarding Titanium, made by Inter Wrap, which is a synthetic WRB made for roofs. I don't understand the claim that such products will rot a roof, as roofing felt is almost as impervious to air, so it seems ill founded. For your area, I would check into ice barriers and follow local recommendations. We don't have such problems in the South, so I am not versed on their use.

 

In our area, it is most common to put one, if not two rows of ice and water shield along the bottom edges of the roof and down the valleys. Personally, I have never put it down gable ends but I know some do. Its all what you want to pay for, ice and water shield is expensive, but it is like a backup plan or type of insurance for your roof. As far as underlayment, #15 is still the norm... in some areas code requires 2 layers of felt and many are using synthetic felt nowdays. When I dont use #15 felt, I'm partial to the Grace underlayment at HD.

I have only rarely seen any water damage under shingles along gable ends, and it has always been because the shingles were cut too short... also when the felt was laid on top of the flashing rather than under it. Shingles should always extend beyond the metal drip edge.

 

are the synthetic or other types of underlayment other than the 15# superior or just different as far as water infiltration or protecting the deck of the roof?

 

I am replacing my roof next month and was told Florida no longer allows 15lb or 30lb Felt underlayment.

There is now something called peel & stick or some kind of synthetic.