Tuesday, 2 June 2015

Beech Gardens, Barbican EC2 - Creation of a new garden by Nigel Dunnett

In the introduction to The 1959 Proposals & Final Scheme for the Barbican the architects Chamberlain Powell & Bon set out their ambitions 'Despite its high density the layout is spacious; the buildings and the space between them are composed in such a way as to create a clear sense of order without monotony. Uninterrupted by road traffic ... A quiet precinct will be created in which people will be able to move about freely enjoying constantly changing perspectives of terraces, lawns, trees and flowers seen against the background of the new buildings or reflected in the ornamental lake' .

‘.. key elements are the vistas between the blocks and the disciplined landscape, here given hard lines of fountains and formal squares of trees. There are 23 acres (9.3 hectares) of open space, including 12 acres (4.8 hectares) of public walkway … where planting was set in large concrete boxes, some of storey height to permit trees to be grown.’ Chamberlain, Powell & Bon by Elain Harwood (RIBA Publishing) 2011

The original landscaping at Beech Gardens was sparse, formal with giant concrete planters and set out over a grid pattern. By the late 1960s early 1970s the residents wanted a softer look. Hence the construction of raised beds that meandered across the expanse. It was planted with trees and shrubs interspersed with seasonal planting. An irrigation system had to be installed to ensure the trees would survive in such a shallow depth. Over time it was a concern the trees were growing too large for the site, remember Beech Gardens is effectively a roof terrace. Plus the business premises below, complained of damp and water ingress which could have been caused by several things including the age of the building, possibly blocked drains or part failure of the watering system.  The jury is still out, but something had to be done and extensive work began.

In these two pictures you can see Floradrain© Powerful drainage and water storage element of thermoformed hard plastic for use on intensive green roofs and roof landscapes. It is made from recycled plastic.

Below there is Geotextile of thermally strengthened polypropylene, applicable as filter sheet above drainage elements for normal mechanical stress.  This is only one of three layers each lightweight including FLL tested, hot air weldable sheet, applicable as root and rhizome protection for extensive and especially for intensive green roofs.

The top layer of tiles were removed to fix and waterproof, a long project which is only just coming to an end. The meandering raised beds have been reinstated exactly as before but with a four layer system to avoid leakage of water into the area below and yet nurturing the plant stock above.
A special seal has been set down to stop water seeping through, on top of that a sustainable urban drainage system, the black upside down containers, allow water to drain through but also retain water to become a mini ‘reservoir’ to allow plants to absorb the moisture. A further covering of fibrous absorbent material to again hold moisture and to support the growing medium above.

Substrate "Zincolit Plus" Mineral Substrate for extensive greenroofs in single or multilayered constructions (made from crushed high quality brick - again a recycled product).
System Substrate "Roof Garden" Substrate consisting of Zincolit (high-quality crushed bricks) and other selected mineral aggregates, enriched with Zincohum (subnstrate compost enriched with fibre and clay materials). Particularly suitable for intensive green roofs with demanding perennials. Deeper thicknesses can support shrubs, bushes and tr5ees. The vegetation can be established by planting plug plants.

A shallow lake will be reinstated also under and around the overhang with planting recommended Nigel Dunnett.

The original tiles that covered the area were made and imported from Portugal in the 1960s, it has been a long and difficult task to find a suitable replacement to satisfy English Heritage and the Grade II listing (as a whole) of the site.

The residents wanted trees again and that is understandable, but no irrigation system is to be installed, thus the complex system of layers to retain moisture as described above.  As trees grow they get weightier so their position within the landscaping is paramount. Only 14 trees will be planted on a grid system, they will be set over the pillars that support the structural loading.  A hose pipe facility will be provided for any necessary top up during particularly dry spells.  The trees need to be planted within a narrow time frame so the pressure was on.

Photographs taken in 14th April 2015

Trees planted are silver birch, flowering cherries, prunus serrula. Shrubs will have leaf and berries to give year round interest or colour such as mahonia and spindle berry. Additional to the trees and shrubs will be 22,000 plants which had to be planted no later than the end of March, choices again to encourage bio diversity and nectar rich.

Here are some of the plants included in the extensive list of over 50 varieties:

Sedum ‘Jose Augergine’
Achillia ‘Terracotta’
Euphorbia characias 'Humpty Dumpty'
Thymus ‘Silver Posie’
Salvia 'Caradonna'
Limonium platyphyllum

Photographs taken on 6th May 2015

The design and implementation is under the auspices of Nigel Dunnett, famous for his Gold Meadows at the London Olympic Park 2012. As a renowned roof garden expert we hope his creation for the City of London Corporation, the Barbican residents and the public, will be a great success. A challenge indeed as the whole project has been up against the clock from the beginning. The results? Only time will tell, as people with gardens, and responsibility for them, know.

Beech Gardens is accessible to the public and is featured in Open Garden Square Weekend 13/14 June. Louisa Allen from Open Spaces, City of London Corporation will be giving a tour on Saturday June 14th at 10am. Well worth a visit.

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