I am not a builder by trade, but building my own house and shop. These are located in the phoenix metro area.
I am getting ready to set trusses and sheath the roof on the shop. We will be using a tile roof. I am looking for feedback on people’s choice of underlayment. The roof does not have any valleys, but it does have a couple of sections where the roof plane abuts a knee wall on a taller section of the building.
I am building this for myself and have every intention of being here for a long time. If the underlayment fails in 20 years I’ll be the guy fixing it most likely. And like most of us here, I want the absolute best possible product – without breaking the bank…
I have spent a little time reading on this subject here at Breaktime. The choices seems to boil down to two: 30 lb felt or Ice & Water. The downside of Ice & Water besides the cost is the rated lifespan of the product. The downside of felt is that it does not self seal around nail holes, etc.
Since this is in the desert, we don’t have an ice dam issue. We do have long HOT periods to dry stuff out. We also can get a couple of inches of rain in an hour with driving wind – occasionally.
I have read where the felt should be doubled. I saw one description that the doubling is achieved by starting with a 19″ half strip at the eaves and then overlaping each run by that much. That versus running one full covering of felt and then start over again at the eaves and running the second.
Any advantages, theories on combining the two products. Since I don’t have any valleys, would there be any benefit of using the I&W at the roof/wall intersection? The building is being made from Rastra (ICF material) and the flashing at this intersection will be kerfed into the Rastra block. So any I&W run up the sidewall will be no taller than the flashing.
I have not priced either approach yet. Can someone give me a rough price comparison for any sized roof for felt vs. I&W?
Thanks for the great feedback.