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Planning a Pond - Pond Liner Underlay

21st Nov 2019

Aquatic underlay is a geo-textile fabric membrane which is rot proof, will last a life time and is extremely puncture resistant.It is essential to use underlay when constructing your liner pond. Once the pond has been filled, the weight of the water can put tremendous pressure on the liner, even a relatively small 1,000 litre pond holds 1 tonne of water. The underlay offers protection from stones and rocks which would otherwise penetrate your liner’s underside under this weight. Underlay also protects the liner from roots which could penetrate and puncture the liner.

Less experienced pond builders have used carpeting, newspapers and hessian as underlay. These materials will rot over time leaving insufficient protection for the liner, and some make-shift underlays can release chemicals as they begin to deteriorate which can cause the liner itself to degrade.Underlay should always be fitted before laying liners as all liner guarantees are invalid if an aquatic underlay is not used.Underlay can also be used to protect the top of a liner if rocks, monoliths or large statues are going to be placed onto the liner in the completed pond.

Permalay Underlay

Permalay is an underlay which is used in the construction of reservoirs. It is incredibly strong, much more puncture resistant than it first appears, and is very light and flexible making it very easy to fit.


Polyfibrelay is a thick, soft underlay which is exclusive to Bradshaws Direct. The extra density of this underlay gives the pond liner even more protection. Polyfibrelay is recommended if the ground is quite stony, or for larger ponds where the waters mass puts more pressure on the liner, which may require extra protection.