I think that really depends on your location and environment. Here in Idaho the majority of roofs utilize a felt underlayment or similar. The peel and stick (commonly called water and ice shield) is used depending on roof design.
Ice and water typically goes 24-36" inside the heated area. This means past the eave and exterior wall. We have had great success with the new breathable underlayments (deck armor). They are light, easier to install, and safe to walk on. Ice and water will make working very dangerous on a whole roof. On low slope applications less than 5 pitch I could see Ice and water on the whole roof then deck armor if you want to go all the way or just I/w . Your shingle manufacturer will have acceptable warranty specs. You’ll want to consult them. 30lb felt will do the job but IMO is for cost saving better products abound. -Josh
As roofing company, we prefer to line the first 3’ of the roof with the self stick membrane (storm guard) along with valleys and any area that water tends to have higher saturation. I.E. Low pitch roofing, rear/upper area of chimney. From that point, we use a synthetic underlayment Vs. 15lbs & 30lbs felt paper. Certain shingle brands require synthetic underlayment to allow full warranty protection. DLP Construction uses GAF architectural HD shingles that require the GAF synthetic felt buster underlayment. Not the most expensive but not the cheapest either. We haven’t had any problems using it and it also has a nice grip/slip protection.
-DaVe Palmer
(Owner/Operator)
As the other contractors have stated in colder climates where ice damming can occur peal and stick or ice shield is required. Typically coverage should be 24" into the heated structure. After that a breathable underlayment is best. Installing ice shield on the entire roof requires exceptional ventilation or the wood will rot. Be careful, make sure to hire a factory trained installer.
Always follow the recommended use of ice and water shield from the manufacturer and use ice and water shield from the same manufacturer as you are getting the shingles from. This is important or they will not honor their material warranty. I typically use GAF Timberline HD shingles, Weather Watch Ice and Water shield on the first 3 feet on all rakes, eaves, around vent pipe collars, chimneys and wall junctures. If you don’t have ice and snow in your climate, you don’t need it at all. As for felt, I use Shingle-Mate from GAF.
There are several types of peel and stick materials. Most are ice and water shield products but some are actually peel and stick base sheets and cap sheets also used in flat roofing conditions, such as when your low slope porch roof meets your steep slope shingle roof.
Ice and water shield is usually used to prevent ice damning from leaking into your home and it is properly installed 3’ minimum from the interior wall of your home not including the eave. We not only install our ice and water shield at the eave location but also the gables,(the edges going up the slope), the valley’s, (the junctures of two roof elevations), all rising walls including complety around the chimney’s and any roof penetration. The balance of the roof area is covered with synthetic underlayment that will not wrinkle when exposed to the sun. They are also slip resistant which protects our team.
Ice and water shield is also installed under shingle roofing when the slope of the roof is 3" in 12" and less.
Peel and stick flat roofing products are both smooth surfaced base sheets and colored granulated cap sheets. They can be installed over low slope roofing and are installed in plies. Such as 1 ply of peel an stick base sheet and one ply of peel and stick granulated cap sheet. For longer lasting flat roofing systems we can install a second layer of peel and stick base sheet for a thciker roofing system. Remember that seams are staggered at each ply layer by 18" and please install base flashings as detailed by the NRCA.