I am preparing to replace a 22 year old flat concrete tile roof and have 2 options for the waterproof underlayment. Use the standard 30# flet with a hop mop 90# layer which is what the old roof has. Or use a newer method manuf by GAF that uses a 1st layer of "DeckArmor" in place of the 30# flet, followed by application of a peel and stick waterproof layer "UnderRoof2". New flat concrete tiles will be installed using adhesive foam.

I am familiar with the older hop mop system, but an looking for guidance on if the newer system is better?

Maj, my company is a registered GAF contractor and I can attest that using the DeckArmor and applying the UnderRoof 2 will save you time and money considering the prices of asphalt. http://www.gaf.com/Content/Documents/21019.pdf is a link to the UnderRoof2. This product is self-adhering so the work is a bit easier and there isn't special equipment needed to install. The DeckArmor link is: http://www.gaf.com/Content/Documents/21021.pdf. Synthetic is the way to go even for shingles. Price per square is a little higher than #30 Felt, but the savings in labor is worth it. Hope this helps.

I agree with dawgsandkats.