There is no shortage of quality underlayment products being manufactured and distributed for use under metal roofing.
While most agree traditional 30-pound felt is not the best solution for long-lasting metal roofing projects, synthetic and peel-and-stick products cost a little more. Are they worth it? Those of you concerned about using the best products with the metal roofing you install would say yes; as would all of the underlayment representatives we asked about underlayment products.
Metal Roofing Magazine asked three questions of several underlayment manufacturers. Here are our questions and their answers.
What benefits of synthetic and/or high temperature underlayments make them more suitable for residential metal roofing jobs than felt?
Bruce Hayden, Alpha ProTech: Some of the synthetic underlayments today contain polymers, which can handle high temperatures. This is critical as they will not melt or soften, thus keeping the underlayment from marrying to the backside of the metal roofing. This then eliminates the need for a liner sheet. This is key in keeping the integrity of the underlayment. Also, because synthetic underlayments contain no asphalts, they become installer friendly in the fact that once you walk on them and then back onto the metal roofing you do not track asphalt back across the metal.
Christine Welby, Grace Construction Products: synthetic roofing underlayments featuring an advanced skid-resistant technology, provides a superior walking surface in both dry and wet conditions on steep-slope applications. Synthetic underlayments can be exposed for longer periods of time than peel and stick products thus, allowing work to continue while the builder dries in the roof.
Tim Williams, InterWrap: Unlike felt, synthetic underlayments do not leech oils or emit fumes which makes it a clean and environmentally friendly product. High-temp synthetic underlayments do not require a slip sheet between underlayment and metal roof, allowing metal to expand and contract freely, high-temp synthetic underlayments won’t dry out or crack as they are able to withstand hot temperatures.
Mark Strait, Kirsch Building Products: The list is long, wind, UV and long term moisture resistance to name a few. It’s like comparing a paper bag to a bulletproof vest. I think the better question would be what benefits does tar paper have over premium synthetics: still some price advantages in the short term although tar paper and SBS underlayment have no real value when comparing the long term features and benefits of a premium synthetic underlayment. There is really no intelligent reason to use asphalt based felts/underlayments, in my opinion.
David Nemes, Nemco Industries: Synthetics are lightweight and exceptionally strong. They do not tear easily and are originally, specifically designed for metal roofing applications. Synthetic underlayments were initially used in Scandinavia, where metal roofing became very popular in the 80’s and 90’s and eventually covered a majority of all the high-end residential roofing.
Mickey Gay, Perma “R” Products: Synthetic underlayments offer superior strength and lighter weight as compared to traditional felts resulting in less waste and faster installations. In addition they can be left exposed for longer periods of time without compromising their integrity.
Sandro DiPede, SDP Advanced Polymer Products: The long-term resistance to higher temperatures experienced in metal roofing is a key benefit of high temperature synthetic underlayments, and specially formulated high temperature self-adhered underlayments is a major reason why these products are far superior to felt paper. Felts will dry out and crack over time, thus comprising their water shedding capabilities as a waterproofing underlayment.
Steve Ratcliff, Tarco: Saturated felt becomes dry and brittle over time. This process is accelerated by heat and, because temperatures can soar beneath metal, becomes an even greater problem for metal roofing applications. Saturated felt can be exposed for only a few days. If the metal roofing happens to get damaged or blow off due to a weather event, the advantage of the peel-and-stick products is obvious. They adhere exceedingly well to the deck and seal around nail holes. Saturated felt nailed to the deck will either blow off or, once exposed, might not prevent the massive water entry that could occur with high winds and rain. In some cases the water damage can be catastrophic.
Sal Catanese, Underlayment Specialties Plus: Well, the synthetic underlayments have no “asphalt” in them and will not dry out over time under the UV rays like the felt paper will. Because of the asphalt in felt, roofers would use a slip sheet (rosin paper) in between the felt and the metal roof, so the felt paper wouldn’t stick to the backside of the metal when it was hot. Also, most metal roof installations take a long time to complete and most of those roofs are left exposed to the weather and sun for quite a long time. Synthetic underlayments do a much better job of staying on the roof and protecting it from the elements.
For metal roofing applications, commercial or residential, what are the advantages and disadvantages of peel & stick products vs. those fastened with caps or other fasteners?
Hayden, Alpha ProTech: The first thing is the cost associated with peel & sticks. From there a peel & stick creates and entire barrier and keeps moisture blocked in the dead area of a roof. Also any moisture build up from the metal side is trapped between the metal and peel & stick. With mechanically fastened underlayments it does allow for a breather area to release the moisture out. The time to install a peel & stick versus a synthetic underlayment reduces overall labor cost and still offers all of the protection that is needed under the metal roofing.
Welby, Grace Construction Products: Peel & stick products have a distinct advantage vs. synthetics when it comes to waterproofing. The product is 30 mils (0.76 mm) thick making it easy to handle and apply.
Strait, Kirsch Building Products: Advantages when comparing against low-end lightweight synthetics are nail sealability and abrasion resistance. In general, premium self-adhered products, when installed properly, provide a better seal along the roof perimeter and between vertical and horizontal laps, higher wind resistance and some self-adhered products can be installed to and over concrete, fluted steel decks, foil /fabric faced Polyiso and DenDeck.
Williams, InterWrap: Both mechanically fastened and peel & stick are relatively quick to install. The advantage with peel & stick underlayments, the likelihood of water penetration at laps is not as big of a concern as with mechanically attached underlayments where wind driven rain may be a factor in overlap areas. The disadvantage of mechanically attached underlayments installed with cap and nail under standing seam metal is cap profile dimpling the metal.
Nemes, Nemco Industries: Peel & stick products are non-breathable and by their nature, can hermetically seal the entire roof deck. This method of application, although they are fully waterproof, bring along their own side effects, such as poor breathability. Therefore, the aforementioned type of installation does require good ventilation in order to prevent complications such as mildew and rot. Underlayments fastened with cap and nail, do allow some degree of air flow, or ventilation.
Gay, Perma “R” Products: Peel & sticks offer a water proofing substrate for roof overlays versus mechanically fastened synthetics, which act more as a secondary water resistant back-up to roof covers. The mechanically fastened synthetics are more cost effective and easier to install than peel & stick products and especially effective on slopes greater than 4:12.
DiPede, SDP Advanced Polymer Products: Peel & stick or “self-adhered” underlayments are required to meet ASTM D1970, which includes a test method for nail sealability. For extreme weather performance, self-adhered underlayments provide the ultimate in underlayment waterproofing capability.
Ratcliff, Tarco: To put it simply the peel & stick products generally require less labor to install, offer a substantially better working surface for the metal roof application and don’t leak. Most of the synthetic underlayments are basically plastic sheets that do not seal around the fastener, thus the reason for capped fasteners. Even saturated felt, because of its asphalt saturation, seals better around fasteners than the synthetics.
Catanese, Underlayment Specialties Plus: Peel & stick products normally seal around the nails in normal installation conditions. Synthetics will stretch around the nails in normal installation traffic conditions. Sticking to the deck may carry an advantage over mechanically fastened in helping to reduce ice dams because of the freeze thaw condition.”
How has the economy affected your business in 2009 and what are your projections/hopes for the rest of the year?
Hayden, Alpha ProTech: Our business has increased over the past two years. The things we attribute it to is a greater knowledge of synthetics and an acceptance of it being a superior product over conventional asphaltic felts. Our prediction is to continue to increase business as this acceptance grows even further. When you install a metal roof you are making an investment above conventional roofing products thus you want a premium underlayment to enhance that performance. As this trend continues, so will the use of synthetic roof underlayments.
Williams, InterWrap: Our business has not escaped the effects of a poor economy. We expect to gain momentum here in the last half 2009 as we begin to see the housing market stabilize.
Strait, Kirsch Building Products: Caused me to look for new opportunities. Thought the government would stay out of the way of business and let the cycle of supply and demand revive the economy.
Nemes, Nemco Industries: The markets in year 2009 have definitely affected our business. The economy has taken its toll, however we estimate that by the spring of 2010, we will experience a turnaround and the markets will have seen the worst. Re-roofing will pave the way for roofing contractors, followed by a slow but steady increase in new residential construction.
Gay, Perma “R” Products: 2009 has been challenging due to the economic slow down. However, our underlayment business has been steady and has grown compared to last year due to reroofing opportunities and market acceptance of synthetics. We expect the last half of 2009 to show slight improvement over the first half as we see the beginnings of a slow recovery.
DiPede, SDP Advanced Polymer Products: The economy has provides a macro “head wind”, but our business is thriving due to the vastly superior value proposition of our Palisade line of underlayments vs. traditional felt paper, and competing self-adhered underlayments. This value proposition superiority is most evident in metal roofing, where the incremental cost of moving from felt paper to our Palisade synthetic underlayment is very small fraction of the overall roof cost, but delivers vastly superior performance.
Ratcliff, Tarco: For Tarco, underlayment sales figures for this year actually are above those for 2008. Tarco is continuing to gain market share as it builds its reputation as “the underlayment company.” Meanwhile, the total market for new types of underlayment products is expanding as more contractors and building owners recognize their value. The LeakBarrier product line is the fastest growing part of our business. It includes self-adhering (or peel-and-stick) products as well as a new asphalt-saturated high performance polyester (HPP) underlayment, which is an easy-to-handle alternative synthetic underlayment.
Catanese, Underlayment Specialties Plus: “My business is new and we and can not gauge the economical affects on it because of that. Our customers realistically have picked up a little because of the summer building season, but I wouldn’t project any great recovery this year.