Synthetic felt

I have never used it and never will. I have seen light fixtures dripping water, mold as far as the eye can see all from a non-breathable synthetic. Now I know these roofs were under ventilated and slightly under insulated. Yes there were bathroom exhaust vents that were not hooked up properly with adapters and clamps and basically stapled and pointing in the direction of the exhaust opening. Many things were wrong with these roofs and needed to be addressed.

"(unless you're just a stubbrn fool)."

Not me, but I see one in the mirror in the morning. :laugh:

After getting burned in the '80's with a lightweight felt replacement, I was reluctant to use synthetics for a long time.

In my climate, at least one/third of the year we are faced with drying in a building that the framing wood is saturated with moisture. This results in the felt wrinkling terribly. Overnight a smooth felt job will turn into a wrinkled mess. The wrinkles can push the felt right through the staples, creating leaks. I had developed strategies to combat this, I would use old takeoff air vents on the dry-in and only stapled the felt at the laps. Since we usually installed battens/counterbattens as we felted, the felt was secure.

While these methods helped, they didn't eliminate the problem of wrinkling. In the late 90's, I started trying synthetics and they stop the wrinkling as advertised. They also withstand the long exposures I deal using tile, waiting for other trades to finish above the roofline. There were some drawbacks, though and I still wasn't satisfied until I used Titanium 50.

If you're going to badmouth synthetics, I say you should at least try the Titanium 50. You will find the walkability, strength, flexibility so far superior to the best 30 lb felt that it will change your mind (unless you're just a stubbrn fool).

Synthetics are great if your leaving them exposed to UV. I've had titanium over my chicken coop for about 14 months, maybe longer. I really need to split some shakes!

Why can't everyone see the logic like that? Ventilation and air movement are so important and so overlooked and ignored.

"I have seen light fixtures dripping water, mold as far as the eye can see ..."

I have seen those things too, when it is very cold outside, because of humidifiers on the furnace that were set too high.

I've only used the synthetic underlayment a couple of times but I don't see the need for it. 15#, 30#, synthetic, once you shingle over it there are so many nail holes in it that I fail to see a difference. I suppose if you are tearing off and not shingling it right away there could be an advantage.

If the air is moving beneath the roof deck, none of those things will happen. You do have to hjook the vents up to a proper hood though.

sorry started and got interrupted before I could finish the post..... to be continued.