[Mark Harvey]

Quick question. We used to use Building (tar)paper under shingles, then added Ice and water membrane to the outer edges of a roof. I am assuming there is a "preferred" underlay or replacement for the Building paper. Please advise as to new products and approx. cost difference.

 

[Windows on Wash]

What shingle are you using? I would stay with their version of synthetic underlayment as well as use their parts and pieces so that you have a system's warranty on the roof.

 

[ront02769]

Building paper is still fine. But the ice and water needs to be adhered to the roof deck, not the building paper.

 

[Yodaman]

Personally, I feel that Titanium UDL 30 is one of the best underlayments out there.
The stuff is nealy impossible to tare. Safe to walk on, great grip with a rubber soled shoe, even when wet. The product can stay exposed for 6 mos, so once you have it down proper with cap nails, you are dried in and can take your time getting the shingles on.

Cost is higher than felt, but the advantages are worth the extra cost.
https://buymbs.com/p-11-titanium-udl-30-synthetic-underlayment.aspx