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Question DetailsAsked on 2/1/2014

What is the best roofing underlayment for NE Florida, synthetic or peel & stick?

What is the best roofing underlayment for the entire deck of a 6/12 roof using asphalt shingles, synthetic or peel & stick? What are the pros and cons of each? Does the peel & stick pose any reroofing problems in the future?

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6 Answers


Peel and stick, is prefered from all I've heard, but a roofing pro may have a different opinion.

Peel & Stick, provides a watter barrier, if shingles are blown off in a storm/hurricane. I've heard that it will reduce insurance cost. Even if it doesn't keeping your home dry in a hurricane is worth it.

Our vacation condo board voted to spend an extra $10,000 for it , on a roof being replaced soon. Large second floor roof.


Answered 6 years ago by BayAreaAC


To answer this question one must understand that each was developed as an improvement over an existing conventional roofing material. 30lb felt has long been used as an underlayment for metal roofs, shingle roofs, slate and the first layer of the 30/90 hot-mop system for tile roofs which has been in use for over 100 years. It consists of 90lb rolled roofing hot-mopped over 30lb felt, which is nailed to the roof deck.

Most of today's "peel and stick", or self-adhered (SA) underlayments are made of a layer of high

density polyethylene or polyester saturated in modified bitumen, which is a blend of rubberized polymers and asphalt. This makes for more tear resistance, elasticity and durability compared to the old 30/90 system. It is ideal as a tile roof underlayment and far superior to 30lb felt as a shingle underlayment. In Miami SA underlayment is installed over a nailed-down 30lb. as a better alternative to 30/90 for tile at a comparable cost and an enhanced system for shingles in that it self-seals around the nails.

Synthetic underlayments were developed for use under metal roofs which can last several a lifetime. 30lb and even 15lb felts were used for decades as underlayments but simply don't have the durability to last that long. Synthetic underlayments also provide a Class A fire barrier but do not self-seal around fasteners and that is the basis for the answer to the question - SA underlayments.

That said, be forewarned that an SA adds considerable expense to a shingle roof. In Miami it is sometimes used as an extra layer of prorection in the event shingles are lost in a hurricane. In NE Florida the threat of major hurricanes is not nearly as great and SA underlayment for a shingle roof is more of a luxury. If you are planning on staying in your home for 20 or more years you may consider an SA to extend the life your shingle roof, otherwise 30lb is fine.

Roofer Mike


Answered 6 years ago by roofermike


What about synthetic underlayments like deck defense and tiger paw?

Answered 6 years ago by Guest_9135704


Sure, "Guest", you can go with these but they don't self-seal around the nails. They claim to be breathable and 30lb is marginably breathable but with a properly ventilated attic, so what? They also claim to lay flatter and that's true. Tip: Let the 30lb felt sit for a week or so before installing the shingles. A week in the sun will tighten the 30lb considerably.

I stand by my previous answer: synthetic and SA underlayments in Florida are a luxury.

In other words, 30lb lasts as long as the shingles while performing its primary function - vapor barrier. Pay more attention to attic ventilation.

Roofer Mike


Answered 6 years ago by roofermike


The standard woven polypropylene "synthetic" underlayments are not breathable unless they are microperforated or specified as otherwise.

The roof doesn't need to breath through the sheathing and 30lb felt is marginally permeable.

I prefer a vapor barrier on the roof to resist the solar vapor drive from the roof down. Ventilation should be handled at the soffits, ridge, etc. if that is the approach of the roof assembly.

The synthetics are better about keeping water out but are not a true self-healing penetration. If you use the plastic cap nails with them, they do a pretty good job of keeping the water out.

The reason I prefer them over felt is largely because of the increases tear resistance and resultant blow off protection when compared to felt. The point is largely moot if the roof is going straight back down through.

Not a huge fan of peal and stick over everything as they usually heat weld to the shingles and then you are stuck with trying to re-deck the roof the next go around.

Answered 6 years ago by WoWHomeSolutions


Two thoughts on the prior comments:

1) RooferMike talks about leaving the felt exposed for a week to shrink. That would be fine if you can guarantee sunshine - I don't have that kind of pull with mother nature. In fact, I do a roofing or paving job and it seems she whips up a special rain squall just for me. The problem with leaving it exposed is if ti gets rained on it absorbs water, and gets wrinkled - just like your skin in a long water immersion. This creates slack in the felt and bulges that can show through as waves and ridges in the shingles - especially with the much thinner, lighter weight shingles in use today. I would not risk it - strip the roof, put down the underlayment, and reshingle as fast as possible.

2) WowHomeSolutions mentioned an important thing - some of the peel and sticks stick TOO well. When you go to reshingle, not all the underlayment comes up, but if you leave it on you get ripples and step-ups in the shingles, so it can take an unusual amount of scraping and even heating (with attendant fire danger) to get it off.

Answered 6 years ago by LCD

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