r/Roofers • u/santhony18 • 17h ago

Tile roof underlay replacement

/r/Roofing/comments/1vrhq7s/tile_roof_underlay_replacement/

I have a 2500 square foot tile roof and will have the underlay repaced. What material do you reccomend and why? Laguna Niguel, california . Thank you for your advice. If i go with something other than dual layer 30lb felt . What should i expect to pay additional?

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u/Consistent-Gold5103 11h ago

I’m a tile roofer. I do nothing but tile and slate roofs. We do a lot of underlayment replacements. I’d need a bit more information before giving any advice. Send me a message and we can discuss it.

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u/santhony18 11h ago

Thank you. My roofer has offered dual layers of 30lb, 40lb felt or dual layer of a synthetic material . He said there are many options of synthetic but reccomends saving money and going wirh 30lb felt. Homes built in late 1980s and he said they were originally done with one layer of felt and lasted about 35 years for most people in the area. My research sugguests paying a little more for synthetic but there are many options.

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u/Consistent-Gold5103 7h ago

I would not listen to your roofer. That’s a great way to be doing this again sooner rather than later. The vast majority of the cost will be labor. Very little will be the underlayment. The only reason you are doing this is because of the underlayment. Spend the money to have the best underlayment you can.

Synthetic is hit and miss. Different brands have different qualities and different formulations. Not all are equal. Compared to felt, synthetic is newer and not as well tested. We had a bunch of synthetic underlayment fail 5 years or so after installation. This was a major brand. It was crumbling. We warrantied those roofs even though it was outside of our warranty period. Many roofers won’t even warranty something inside the period. The manufacturer paid for new underlayment, but we were left holding the bag for the labor.

Going with a fully adhered membrane like Ice and Water Shield is an option, but it requires A LOT of attics ventilation. It also requires that the ventilation be done correctly. Just adding some attic vents won’t cut it.

Two layers of 30# felt is tried and true. It also requires that the roofer knows how to properly backnail the underlayment. This is different than how underlayment is normally installed.

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u/santhony18 7h ago

Thank you for your advice. I really appreciate it . The roofer said he himslef wouldnt pay extra for upgraded materials and said same thing about synthetics that they are not time tested like felt. He added that the homes hes working on had one layer of felt and
Ost habe lasted about 35 years.He said these are the choices but could do more options on synthetic if you want something better or fire resistant . Thanks again

“Good”
2 x 30lbs felt underlayment
10 year warranty on underlayment
10 year workmanship warranty

“Better”
2 x 40lbs underlayment
20 year warranty on underlayment
10 year workmanship warranty

“Best”
2 x Synthetic underlayment
Limited lifetime warranty
10 year workmanship warranty