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15yearsagoBy Douglas M. Roth

‘As modern building materials have been developed,’ wrote Japanese garden specialist Douglas M. Roth in October 2003, ‘we humans have been remarkably proficient at applying them in ways that go well beyond the vision of their inventors.  Such is the case with roofing membranes, which now are widely used as liners for backyard streams and ponds.  

‘It’s understandable that landscape designers and contractors have taken to these rubber liners.  After all, they make pond and stream construction inexpensive and easy.  But from the perspective of the Japanese gardener or quality watershaper, convenience and affordability alone do not qualify a material for use.  Instead,’ he continued, ‘standards of durability and enduring beauty must be applied.’


‘[R]ubber liners have numerous drawbacks when it comes to creating quality ponds and what are known to Japanese gardeners as yarimizu, or winding streams.  Most of these problems emerge only with time, and because they are not always immediately apparent, many quality-minded people have been lulled into a sense of security and comfort.’


‘[W]hen you strive to create enduring works of art – which is presumably what quality watershaping is all about – then using a material that is impermanent, subject to punctures, difficult to repair, and completely lacking in structural support is ultimately self-defeating.’


‘To be sure, there are several different liner types and grades and mil thicknesses out there, and some are more durable than others.  Many have projected life spans that exceed 30 years – a significant improvement over products that were offered not too many years ago.  But if you think about it, three decades isn’t long at all.  Consider our common worlds of art, architecture and landscape gardening.  How old is that painting on the museum wall?  How old is the house you live in?  More to the point, how old are the noteworthy gardens in your region?’


‘Among the several bones I have to pick with liners, the most important is the fact that replacing a damaged liner almost always involves ruining the environment the liner was meant to sustain.’


‘To replace that liner, you’ll have to lift up the multi-ton boulders along the edge.  And to do that you’ll likely need to bring in heavy equipment, which means the disruption won’t be limited to the watershape’s footprint.  There’ll be a pathway for the machinery, a place to store rocks and working room around the vessel to allow for installation of the new liner.  In other words, to replace the liner, you’re going to completely destroy the pond and much of the rest of the garden in the process.’


‘It’s my view that there are far better materials for waterproofing ponds, streams and cascades.  The famous, centuries-old ponds of Japan, for example, are all lined with clay – malleable, waterproof, self-sealing (to a certain extent), inexpensive and reparable without the need to tear everything apart.  Of course, leakage isn’t a huge concern in those venerable bodies of water because they are typically fed by nearby streams or rivers, and a certain amount of leakage is expected.’


Clay still might play a useful role in larger modern waterfeatures, but for backyard ponds and swimming pools I recommend steel-reinforced concrete – gunite, shotcrete, poured in place or hand-packed – as the best way to create permanent high-quality pond and stream structures.  When properly engineered and installed, these structures can last centuries without disintegrating the way liners inevitably will.’


‘Watershaping is the bridge that brings us together in ways that neither [pool contractors nor pond installers] probably ever considered possible.  This notion of using concrete instead of liners to create more permanent structures,’ Roth concluded, ‘is a prime example of where the convergence could and should begin.’  

How has this discussion evolved in the past ten years?  As a pond installer, do you ever work with concrete as an alternative to liners, or do you stick with rubber?  As for pool builders, have any pond installers asked you for input of a technical sort?  Please do share your thoughts on this interesting topic below!


Douglas M. Roth is publisher of The Journal of Japanese Gardening.  Widely considered to be America's leading authority on Japanese pruning techniques, he is a graduate of the U.S. Naval Academy in Annapolis, Md., and served for six 6 years as a naval officer in the Philippines, Hong Kong and Japan.  He resigned his commission in 1988 and established The Isshiki Zoo, an English language school for children in Hayama, Japan.  After passing the National Language test, he began a five-year gardening apprenticeship in Kamakura and became the first foreigner qualified to practice gardening in Japan.  His company, Roth Tei-en, designs and maintains Japanese gardens throughout North America.

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