Saturation vs. Lamination

And why it matters on your roof

When it comes to waterproofing and mils, it all depends on whether the membrane is “laminated” or “saturated.” Common among single-ply systems, a membrane consists of a bottom layer, a polyester matting or scrim in the middle, and then another layer on top, which are all laminated together by a machine in a factory, to make a single sheet.

When the membrane is laminated, the top waterproofing layer above the scrim (or middle polyester layer) becomes very important.

TPO product sheets typically show around 15 mils of waterproofing above the scrim on a 45-mil product.

What does this mean? NRCA studies tell us that single-ply roofs wear an average of 1-2 mils per year. So if you only have 15 mils above the scrim, you can expect the top waterproofing to be worn halfway – or more – to the scrim in just 10 years.

It’s our position that once you get to the scrim you’re in failure mode. You’re much more vulnerable to leaks because at that point, you’ve lost most of the waterproofing protection.


Laminated sheets are prone to peeling, and one puncture through the top sheet can compromise that section of roof because it exposes the scrim. With a saturation technique, you have the same, continuous consistency of waterproofing throughout the entire membrane.Lamination vs. Saturation

Metaphorically, consider lamination as a pressed wood desk with a protective sheet as the top layer; while saturation is more like a solid wood that, even when chipped or scratched, still maintains its strength and integrity all the way through.

Not only does a saturated membrane enable all its mils of waterproofing to truly and practically work for you, but internal tests have documented a wear rate that’s much slower than NRCA’s data on TPO membrane wearing.