Wet Felt vs Wet Synthetic Underlayment

Roofing in the winter can be challenging because of the chance of rain. One of the biggest problems roofing over wet or damp felt is that the felt absorbs water and can buckle or wrinkle. Even though the felt is water proof and protects the roof deck, roofing over these buckles or wrinkles can telegraph a wrinkle through the commonly used asphalt shingles, making an unsightly finished product. The #15 felt is susceptible to wrinkles more than the #30 felt because it is thinner. Weathered felt can look horrible and just walking on wet felt paper can be very slippery and dangerous. So installing roofing over wet roof felt is not recommended, but sometimes we have no choice . . . . . or do you?

Black roofing felt, sometimes called tar paper, comes in #15 and #30. Both are made from thick paper and fiberglass materials that have been saturated with asphalt to make it waterproof. This makes it very useful for construction, primarily for the roofing industry. Years ago organic felt paper weighed 15 lbs. and 30 lbs. per square, but it has changed since the introduction of the lighter fiberglass matt into the layers. It has become less in weight and referred now to as number 15 and number 30 felt. For over a hundred years we have used this felt paper with no other choices, but now with the new synthetic underlayments available, you can avoid the dangers of slipping and the unsightly wrinkles caused by wet felt.

Titanium® UDL 25 is a synthetic underlayment does not absorb water and therefore will not wrinkle when it gets wet.  UDL 25 is water proof when fastened properly. Using synthetic underlayment allows roofing contractors to re-roof even they can’t finish in one day or when rain is coming. This keeps your crew working in the winter and your production does not get backed up because of a threat of a few showers. Even roofing when UDL 25 is wet, the moisture will find its way out with a minimum of 4/12 or greater roof pitch. For anything less than 4/12 but greater than 2/12 Titanium® PSU 30 is the best choice. For climates where freezing and ice dams can occur, the Titanium® PSU 30 is strongly advised.

Titanium® UDL25 won’t wrinkle and has a non slip feature.


Rainy Days

UDL25 possesses a revolutionary patented slip resistant Sure-Foot® nodular walking surface technology that allows for easier steep slope walkability, even in wet conditions. It’s also 14 times stronger than #30 felt. This is perfect underlayment for use under Metal, Shake and Shingle Roofing. UDL 25 can be left on the roof uncovered without the need for tarps. Unlike oil saturated felts, UDL25 does not dry out, leach oils in the heat, nor does it become stiff and difficult to roll in the cold.


For more information of the full line of Titanium Roofing Underlayments – visit www.interwrap.com

All data and information appearing on this site is anecdotal in nature, reflecting the contributor’s personal experience and not fact-based research and, therefore, to be used for information purposes only. Read full disclaimer