Final Report Summary

Test Procedure

Green Roof Membranes/Root Barriers were tested for root resistance to Pyracantha and Quack grass in a 2 year greenhouse study based on procedures described in "Investigating resistance to root penetration at green-roof sites" (FLL, 2002) modified as stated in this report.

Materials Tested

SeamFree horizontal field membrane, and the PermaFlash System (MBR Flashing Cement1 with SeamFree Fabric (AKA PermaFlash Fabric) reinforcing fabric for vertical flashings and details and PermaFlash Primer used for repairs outside the Recoat window.

Results summary

  1. The SeamFree and PermaFlash waterproofing system tested in this evaluation appears to be resistant to root damage based on this 2 year test.
  2. Plant growth was equivalent in test and control containers and was adequate for proper test evaluation. Dense root mats were evident at the bottoms of all test and control containers.
  3. No roots or rhizomes penetrated the monolithic SeamFree coatings on the bottoms of any of the test containers.
  4. No roots or rhizomes penetrated the reinforced PermaFlash coating. Reinforcement used in this test was SeamFree Fabric.
  5. No roots or rhizomes penetrated any seams in any test container, including corner seams applied within the-coat window, and repair patch seams applied outside the re-coat window. Seams created outside the recoat window were created following SeamFree (PermaFlash) instructions for coating beyond the recoat window.
  6. Fine roots adhered to the surface and entered air pockets and surface imperfections at the surface of the SeamFree and MBR Flashing Cement1 but did not go through the waterproofing or appear to damage the material. Roots were able to grow under seam edges and drips where materials were not fully adhered.

Precautions when using liquid applied systems

Root adhesion to surface imperfections and air bubbles suggest that care must be taken to maintain adequate thickness of these materials in green roof applications to ensure that none of these imperfections extends through the entire waterproofing layer.

Follow manufacture's instructions for surface preparation in order to maximize adhesion to the substrate to be coated. MBR Flashing Cement1 must be reinforced with SeamFree (PermaFlash) Fabric when used for detailing and vertical flashings in green roof applications where "walls" may be exposed to plant roots or rhizomes.

1 The MBR Flashing Cement used on the walls in the test containers was a slightly modified form with lower asphalt content than the standard MBR Flashing Cement. Standard MBR Flashing Cement was used for repairs. MBR Flashing Cement is a chemically thickened version of the SeamFree. There is no reason to believe that the standard MBR Flashing Cement would perform differently than the actual material tested. Contact the manufacturer for more information on the Flashing Cement used in this test

See complete report for detailed information. Contact Johns Manville for a copy of the full report

The Penn State Center for Green Roof Research in no way warrants (expressed or implied) the products tested, only that the test was conducted as reported and the results of the test were as stated in the final report.


Johns Manville
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Denver, Co 80202