Two data sheets can look equally professional and describe products that behave nothing alike. The difference is usually in which fields are filled in. Use this checklist to read a sheet properly before you compare prices.
| Field | What it tells you | If it is missing |
|---|---|---|
| Nominal and minimum thickness | Thin spots are where the membrane fails first | You cannot assess the worst case, only the average |
| Tensile strength, MD and CD | Resistance to tearing during installation and under load | A single figure hides a weak cross direction |
| Elongation at break | Ability to accommodate deck movement without splitting | No way to judge behaviour over movement or thermal cycling |
| Low-temperature flexibility | Whether it cracks in cold weather, in handling or in service | Risk of winter failures you cannot predict |
| Heat resistance | Resistance to sagging or slipping on a hot deck | Unknown behaviour in high-deck-temperature climates |
| Water vapour transmission | Whether the assembly can dry through the sheet | You may be specifying a barrier where you need a breather |
| Fastener pull-through | Whether it survives wind uplift at the cap nail | No basis for a high-wind specification |
| UV exposure limit | How long it can sit before the finish course | You are guessing on schedule risk |
| Roll size, coverage and weight | Freight cost, pallet count and crew handling | Ordering and logistics cannot be planned accurately |
The most common error in comparing sheets is comparing numbers measured under different conditions. A tensile strength measured at 23 °C is not the same property as one measured at a lower temperature, and elongation tested on a different specimen geometry is not comparable at all.
Tell us the product, roll spec and destination. We will send the current data sheet, test reports and a quotation against your actual requirement.
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