Imperial Wharf, London

Imperial Wharf, London

Type of works: supply and installation of Protecto-drain membrane.

This phase of the project was carried out in the summer of 2008. The client had an area of hard landscaping in a courtyard with a series of planters at various intervals.

These planters had been waterproofed, but, as they were going to be filled with shrubs and other plants, the client needed to ensure two things: that the waterproofing was protected from backfilling and root damage, and that the drainage outlets would not become clogged up and allow consistent free drainage. A membrane that would not leach chemicals or pollute the water run-off was also essential.

Protecto-drain G8 was chosen. The HDPE membrane was lightweight and flexible enough to be folded into the corners and details of the planters easily, without having to be constantly cut and bonded together. It was easy to fix using nails or screws and Wallbarn fixing studs, which seal the holes to prevent leakage. The geotextile fabric bonded to one side also meant a constant filtration layer.

The consistency of the membrane remained intact throughout, due to the superior nature of HDPE material. Wallbarn does not fill its HDPE mixtures with calcium carbonate (unlike some other manufacturers in the market), so no ugly white score marks or weak spots appeared at the folds or creases.

Working around tricky details such as the outlet pipes was easy as the plastic membrane could be cut around the object, and the geotextile fabric could then be wrapped around it, ensuring that a filter layer was always present at the key points.

The planters were lined with insulation boards, which were then filled with soil and planted up with vegetation. The units were topped with coping slabs.

The geotextile acted as a filter layer, allowing water to pass through but holding the soil in place, and the cupped HDPE membrane kept a constant air gap between the structure and the soil, protecting the waterproofing and ensuring no pressure points arose, thereby giving proper drainage at all times.

The planters thrived and gave the whole area a classic, luxurious, natural feel. The vegetation gave an attractive focal point to the pedestrian walkways, and also muffled a lot of the sound and echoing between the tall buildings.

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