Many of the newer roofing companies are opting for using synthetic 30# underlayment over using a more expensive peel-n-stick underlayment. Synthetic 30# is a lesser product similar to duct tape. It has many positive uses but none of them is for being used as underlayment.
Synthetic 30# is a very thin roll paper that is fastened with plastic simplex nails. This is a tremendous vulnerability especially during the rainy season. The fasteners that hold the underlayment in place must be installed perfectly to keep the dry-in from creating a leak issue.
IF the button (or cap) is not seated perfectly when it is hammered in, it will leave a space for water to get in under the button. The underlayment is so thin that it will not create a seal around the nail. Synthetic 30# also tears easy at the fasteners.
When nailing the simplex nail in, it there is any trouble with the application, the nail will wallow out a space leaving bare plywood under the button (or cap) of the nail.
There are around 80 nails per 100 square feet on your roof deck to fasten it into place. An average home’s roof is around 2500 square feet. This means you will have at least 2000 nails fastening the underlayment to the roof deck. How many nails do think are perfectly seated on your roof? Do you feel that your home is protected from leaks when your roof is dried in and waiting for inspection, especially during the rainy season?
The Synthetic 30# is also not a self-adhering underlayment which means to you that the underlayment is not adhered monolithically leaving no space for water to travel under the underlayment. Once water enters through one of the fastening nails, it can run all the way from the top of the roof to the bottom of the roof when synthetic 30# is being used.
According to insurance, Synthetic 30# is also not considered to be a secondary water barrier (SWB). You would need to use a peel-n-stick tape to seal all of the plywood joints first and then you could use the synthetic 30# or the original 30# underlayment over the wood deck. This would meet the criteria necessary for being considered as a secondary water barrier. I have never seen any of the roofs having synthetic 30# underlayment being installed on them also using the peel-n-stick tape to meet the specs for the SWB. This is overcome by each roofing company signing an affidavit that they used peel-n-stick or the peel-n-stick tape and met the requirements. If your home’s roof ever had a catastrophic failure and the insurance adjuster finds that your home did not meet the specs necessary for a SWB rating but had an affidavit that said it did, your insurance would be able to deny your claim.
Synthetic underlayment also relies heavily on shingles to seal and shed the water from the roof. Any water that gets under the shingles on a home that synthetic 30# was used on will overcome the underlayment and leak inside the home. Peel-n-stick is a much safer product that will give you a second layer of protection under the shingles that synthetic 30# cannot give because of how peel-n-stick uniformly fastens to the roof deck leaving no raceways underneath the underlayment for water to travel through. This is a very useful feature of peel-n-stick during hurricanes. Should debris hit your roof and tear through the shingles and peel-n-stick, water will not have a place to go. If debris should hit a roof with synthetic 30# underlayment, your roof will be wide open for water intrusion.
Reroofs in the state of Florida all have to have a secondary water barrier. You must use either a peel-n-stick underlayment or peel-n-stick tape used with an underlayment to meet the codes of having a secondary water barrier. Peel-n-stick tape is very expensive and ultimately will be very close to the investment of using peel-n-stick underlayment nullifying any savings that you might have thought you would receive while getting a substandard underlayment.
The reason synthetic 30# is being used by many of the newer roofing companies is that it is very cheap to purchase and they are not using the required peel-n-stick tape to seal the plywood joints. Will a roofing company that is so focused on installing the cheapest materials so that they can make a profit make repairs to the inside of your home when it is damaged from the leaks?
San Carlos Roofing does not use synthetic 30# as an underlayment. We not only use peel-n-stick, but we use a more expensive self-adhering underlayment. We choose to use Polyglass IRXe as the underlayment for our shingle projects. It is a quality underlayment that we have settled on because of its durability and the granular surface does not come off on our installers’ shoes when it gets hot here in Southwest Florida as many of the lesser peel-n-stick underlayments will do. Our installers are safer on IRXe because the surface of the underlayment will not melt and consequently the installers will start to slide down the roof.
We have been using the Polyglass IRXe for many years now. We chose it mainly for the safety benefits (for the installers not sliding down the roof) and the durability (not losing its granular surface in the heat. Granules will collect on their shoes like black snow. These granules would then mark the new shingles as they walked across a project roof during the shingling phase).
IRXe is also a better product for the customer. For as long as we have used it, it chemically fastens (peel-n-stick glue) evenly across the entire wood deck creating a seal that is far less apt to allow water to leak into your home. We also back nail each course using much stronger, all steel simplex nails that do not have a plastic button. Being that it uniformly fastens to the roof deck, there is a lesser need to use nails to hold the underlayment in place. We only use one line of simplex nails in a specially engineered lap intended for nails (called a nailer lap) at the top of the course of underlayment. This is called back nailing. Peel-n-stick underlayment (like IRXe) uses only one line of simplex nails every 12”. This is in opposition to the four lines of simplex nails every six inches with the synthetic 30#.
IRXe (and most other peel-n-stick underlayments) is self-sealing, meaning that when we do drive nails through the underlayment during back-nailing, the material of the underlayment grabs around each nail penetration, sealing it and reducing the exposure to roof leaks.
The peel-n-stick underlayment does come at a premium. You can tell when a roofing company is quoting the synthetic 30#. Their price will be about $2,000.00 less. Remember, synthetic 30# is not considered a secondary water barrier. You will not meet the criteria for the insurance companies even though it is assumed that the standard is being met. You will not meet the county code on reroofs if you do not use a secondary water barrier like peel-n-stick underlayment peel-n-stick tape sealing all of the plywood joints under an underlayment. If their price is $2,000.00 less, they will not be using the peel-n-stick tape. You will not be getting a roof of equal value. There is a major difference in quality and code specifications.
If you have two roof estimates and one is $2,000.00 less than the other, these estimates are not equal or “apples to apples”. They are not the same. They are of greatly differing qualities. If they choose synthetic 30# underlayment over peel-n-stick, what other lesser materials have they chosen to use on the rest of your roof project?
