The greening of rooftops is increasingly common; gardens provide perfect insulation for roof surfaces which, typically, are exposed to the highest solar radiation relative to other parts of the building. And with the rising density of urban developments, landscaped gardens on built-up areas offer welcome relief from barren glass and concrete structures.
Designers for these projects face the challenge of selecting a secure waterproofing system to prevent infiltration from planted areas into penthouses or basements beneath. The important performance criteria include:
a) Root-resistance: ability to resist damage by root growth.
b) High-performance durability: the waterproofing membrane is concealed beneath the drainage, soil and plantings. Leakages are difficult to trace, and repairs are work-intensive and costly.
c) Physical toughness: during its service life, re-plantings and maintenance will require the removal of the top layers and expose the membrane to abrasion and impact loads.
d) Immersion resistance: from waterings and rainwater.
e) Chemical resistance: from fertilisers and pesticides.
For root-resistance, the EN 13948 test method which specifies a rigorous procedure for determination of resistance to root penetration is a useful reference for designers. In the test, 6 containers are lined with the membrane (complete with corner details and lap joints for sheet membranes) and then filled with soil and planted with pyracantha, an aggressive and fast-growing shrub. These are then monitored over a two-year period at the end of which the containers are emptied, cleaned, and then the linings are inspected to see if they remain in good, serviceable condition as waterproofing membranes.
MAPEI materials which have passed the EN 13948 Standard for root-resistance and, which meet the important performance characteristics listed above for garden membranes, are:
Another root-resistance test standard is CEN/TS 14416. This specifies a less rigorous test which runs for eight weeks (compared to the two-year test in the EN 13948 standard). MAPEI waterproofing materials which pass this test include PURTOP 400 M and AQUAFLEX ROOF PREMIUM.
For technical advice on the MAPEI system which best suits your particular project requirements, please contact us at mapei@mapei.com.my.
Note:
Waterproofing coatings which claim root-resistance should be checked for: (i) the test method against which the claim is made (with details of the test procedure), and (ii) whether they have the robust physical and chemical resistances as described above. Some of them are only suitable for use in small planter boxes or for plantings with non-aggressive root growths.
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