Sika Sarnafil Guaranteed Thickness Program

Thickness Guarantee

All of us are familiar with the old maxim that “you get what you pay for,” and most will readily vouch for that statement’s fundamental truthfulness. But what of single-ply roofing membranes? Do building owners really get what they pay for under current industry standards established by the American Society for Testing Materials (ASTM)? These standards for various single-ply membranes allow a manufacturer to produce a membrane 10 percent thinner (or thicker) than its labeled thickness, meaning that a membrane labeled 60 mils could actually be 54 mils and still be in compliance. Specifiers and building owners are generally unaware of this situation, even though it has a direct impact on product value. And, of course, it goes beyond “getting what you pay for.”

Roofing Membrane Thickness Key Determinant to Longevity

Roofing membrane thickness is a key determinant to longevity, durability and weldability. Roof surfaces have to withstand challenging climatic and meteorological conditions involving moisture, temperature, and solar radiation and wind. Over time, these forces combine to age membranes, resulting in part in a loss of thickness for all products. All other factors being equal, a thicker membrane withstands these forces longer.

In addition, commercial roofs typically host HVAC and mechanical equipment which entail foot traffic for maintenance and repair. Thicker membranes stand up better to punctures and abrasion, in addition to weathering and to aging. The commercial roofing market has generally moved in the direction of thicker membranes as a result.

Membrane Thickness Scuff Test

Other Manufacturers Falling Short

Production techniques utilized in the manufacture of single-ply membranes have advanced over the years and most major manufacturers can now produce membrane thicknesses with great precision. So why do so few companies produce single-ply membranes that actually meet the labeled thickness? The ASTM standards do not require it, but the primary factor is presumably the price-sensitive, competitive nature of the roof manufacturing business. One independent roofing consultant has estimated that the cost to add thickness to membranes is between $.01 and $.015 per sq ft per added mil of thickness. On a nominal 60-mil membrane, the added cost for just 3 mils (5 percent of 60) would be $.05 per sq ft.

A properly executed hot air welded seam is critical to the long-term performance of thermoplastic membranes. Research conducted by Sika and published in the Journal of ASTM International examined the welding properties of five different thermoplastics, consisting of three PVCs and two TPOs2. This study examined the weldability of these materials after immersion in water and exposure to severe soiling. The research showed, among other things, that the telegraphing of scrim through the surface of single ply materials is a detriment to achieving high weld strengths. The thinner the membrane, the more pronounced this effect is likely to be.

In fact, independent testing of fifteen thermoplastic roof membranes in 1998 by the consulting engineering firm Simpson Gumpertz & Heger showed that only the Sarnafil-branded adhered and mechanically-attached membranes and one other membrane from another manufacturer actually met the labeled thickness, with all the other membranes failing to measure up (please select enlarged view to see table on the left of Labeled vs Measured Thickness - 1998).

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In bid situations, competitive membranes may be labeled 48 mil or 60 mil, but in reality only one is likely to actually meet the mil thickness — Sarnafil. Were architects or consultants to specify a minimum thickness rather than a nominal thickness in competitive bid situations, all manufacturers would be forced to supply the same minimum thickness.

Track record should be the number one factor when determining the quality of a product. Bids requiring a minimum thickness, however, would be consistent with respect to thickness and this would allow for a more equal evaluation of the proposals.

Testing conducted internally in 2013 by Sika and involving most of these very same single-ply membranes showed that nothing had changed — again, only the two Sarnafil membranes and one other membrane reached the labeled thickness.

These test results indicate that virtually all manufacturers other than Sika produce membranes at or near the bottom of the 10 percent ASTM tolerance in thickness (please select enlarged view to see table of test results, on the left).

 

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Single Ply Welding

A properly executed hot air welded seam is critical to the long-term performance of thermoplastic membranes. Research conducted by Sika and published in the Journal of ASTM International examined the welding properties of five different thermoplastics, consisting of three PVCs and two TPOs2. This study examined the weldability of these materials after immersion in water and exposure to severe soiling. The research showed, among other things, that the telegraphing of scrim through the surface of single ply materials is a detriment to achieving high weld strengths. The thinner the membrane, the more pronounced this effect is likely to be.

We'll Measure Up, or We'll Pay Up

Sika has a no-nonsense reputation for delivering roofing solutions that withstand the world’s harshest conditions. The Thickness Guarantee Program for Sarnafil membranes ensures that architects and roofing consultants can specify with confidence, and that building owners will truly “get what they pay for.” Roofing contractors can continue to look to Sika as a trusted partner in the installation of quality roofing systems.

This program also heightens both the awareness and the importance of fair product comparisons. A minimum membrane thickness requirement establishes a more uniform basis for comparison when multiple manufacturers compete in a bid situation, and all specified products would be required to meet the same membrane thickness criteria.

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