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Jones of Oswestry steelwork meets challenging demands of flagship Liverpool development

12 June 2008

Chosen for their durability and aesthetics, Jones of Oswestry’s steel landscaping products have been specified by BDP for the Paradise Project, Grosvenor’s £1 billion regeneration of the heart of Liverpool.

Block paving and landscaping materials coverage have been maximised using Jones’ recessed products for paviour infill. They include Suprabloc access covers, Solobloc covers with assisted lift, Telebloc approved, assisted lift telecommunications access covers, and Aquaslot recessed drainage. Special Arborslot recessed tree surrounds were supplied with hinged inset covers providing a watering point to the tree root irrigation system.

Jones also designed over 250 linear metres of bespoke linear slotted drainage combined with Supradrain high volume channels, reduced in depth for installation in shallow concrete slab.  Other special products included a recessed multiple leaf fire-fighters’ access system and a smoke venting assembly, both in stainless steel and with features such as safety barriers, walk-on safety grids and integral chamber ladder.

Grosvenor’s Paradise Project is creating Liverpool One, six interlinked districts over 42 acres, master-planned by Grosvenor and BDP, with another 25 firms of architects designing individual buildings and Laing O‘Rourke, Balfour Beatty and Kier as main contractors. Grosvenor was selected by Liverpool City Council (LCC) as developer for the Paradise Street Development Area (PSDA) project in March 2000.

Jones’ provision of service life data for its products, including certification of the company’s Duragalv post-galvanising, simplified compliance with design life needs in Grosvenor’s QCD (Quality Cost Delivery) document. 

James Millington, BDP landscape architect associate, said: “The client’s QCD document required 25 years longevity from metalwork in the ground, so post-galvanising of steel products was an important specifying issue for us together with assurances of product durability. Performance data provided for Jones’s Duragalv protection system made it easy to demonstrate compliance with durability criteria.” 

Jones applies different grades of Duragalv hot dipped zinc protection – 70 microns, 100 microns or 140 microns - to its steel landscaping products to meet modern service life needs, typically 25 or 30 years for public sector building. Very importantly, predicted longevity takes into account local atmospheric corrosivity and corrosive factors borne in surface water, such as de-icing agents and gritting salts, which can significantly accelerate product ‘weathering’ from location to location.

BDP’s James Millington said: “Jones of Oswestry products meet the demanding, high quality requirements of high profile public realm schemes. Great attention has been paid to the aesthetics of paving designs at Paradise Street and Jones’s recessed products allowed us to minimise the visual impact of metalwork on these crucial landscaping elements“.

Also key to the quality and enduring performance of Jones’s recessed products is the use of 6mm thick steel plate as standard. This minimises deflection, provides increased impact resistance and assures ease of removal combined with the tapered tray design. A full flange on the frame further assures stability of the unit in service.

Risk of a slip

By maximising paviour coverage and minimising metalwork, recessed landscaping products reduce the risk of a slip caused by differentials between paving materials in line with BS 8300: 2001: Amendment 1 and health and safety considerations. They also aid movement of wheelchairs and pushchairs in line with local authority ‘Access for All’ initiatives and their responsibilities under the Disability Discrimination Act.

The assisted, one person lifting mechanism of Jones’ Solobloc and Telebloc units
enabled compliance with other health and safety requirements.

BDP’s James Millington said:Telebloc provides modular design, assisted lifting and a choice of multi-leaf systems that divide access into smaller, manageable covers for easy handling by one person in compliance with Manual Handling regulations. This ease of access also ensures that on-going use of the products, for maintenance access, for example, complies with CDM requirements.”

Jones’ high specification products are a key feature of the Paradise Street district, suiting the quality and aesthetics of the wide, boulevard style design of this flagship pedestrianised retail, housing and leisure complex.

One of Europe’s largest city centre regeneration projects, the Paradise Project will link Liverpool’s existing main retail area with the waterfront and business district, as well as being a key attraction in its own right. It incorporates over 1.6 million square feet of shopping and catering, 625 residential units, together with two new hotels, cinema complex, four storey underground car park, a green park and performance space.

Main building work commenced in autumn 2004 and is due to be complete this summer.  


Jim Ennis Construction Ltd, a public realm works subcontractor to Laing O’ Rourke, has ordered and installed a range of Jones’s products in areas LA3, LA2, LA4b and Discovery Axys.

Darren Durose, contract procurement manager for Jim Ennis, said: “Jones of Oswestry’s service has been first class, from start to finish.

“Their sales team provided very professional technical advice and prompt pricing when we made our initial product enquiries. This was followed by quick and accurate design work by their design department, enabling us to progress approval of special products with BDP very efficiently.

“Manufacture and delivery also went very smoothly, with Jones production department responding on time to our schedule and call-off needs on both standard and bespoke products.”

The precision and quality of Jones’s products were soon apparent to Jim Ennis’s site team during installation.

Darren Durose said: “The products, including specials, were very straightforward to install. Frames and grids went in perfectly, such is the quality, making paviour inlay and abutment to the units easy. Jones offered to send someone to site to trouble-shoot if we had any hitches, but this was not necessary.”

Specialised personnel access systems

Jones designed two pedestrian duty, recessed multiple leaf access systems in stainless steel, infilled with artificial turf to blend with the green space of Chavasse Park.

Providing access to emergency stairs for fire service personnel, the larger assembly has a 5750mm by 1650mm overall frame with three individual hinged covers providing a combined clear opening of 3800mm by 1350mm. Inside, three hinged barrier sections with pull handles can be deployed to create a 1100mm high guard around the chamber together with the main covers and a pair of stow-away gates at the non-entry end of the assembly.

Secondary emergency escape from the chamber is provided by a smaller hinged 900mm by 900mm clear opening cover set inside a blanking plate at one end of the assembly. Opening from the inside only, this provides personnel escape, should the stairway be impeded, in conjunction with a fixed ladder also fabricated by Jones.

The stowed barriers are engineered to provide fall protection resistant to a force of 740 N/M whether mounted vertically or lying horizontally across the chamber. The assemblies also feature drainage spigots within the frame, as well as turn-catch locking and cover lifting points.

At 3500mm by 1500mm overall, a smaller three leaf assembly provides a venting facility for smoke. Inside the cover, three lift-out mesh panels provide fall protection, while permitting pedestrian loads on top.

Surface drainage

Surface drainage for a feature stairway linking Chavasse Park with retail space posed particular problems. The required drainage is installed on relatively shallow building slab with limited depth for surface paving and associated metalwork. 

James Millington of BDP said: “We were unable to meet the application with a standard slot drainage system so Jones designed bespoke units. These allowed us to achieve the aesthetics we wanted but also met technical needs, overcoming the constructional constraints posed by the slab while providing the required drainage capabilities assessed by the drainage engineers, Capita Symonds.”

Jones designed six substantial, continuous drainage assemblies, four being curved-on-plan, to provide drainage for the staircase and adjacent areas.

On top, they incorporate mainly slotted drainage units with 120mm raised drainage slots, interspersed with Aquaslot recessed gratings where access is needed to catchpits or sumps below. Combining to present only slim drainage slots and frame edges, the two products allow maximum paviour coverage and minimise the impact of ground-laid metalwork.

Below, the gratings are teamed with high efficiency Supradrain channels, reduced in depth to just 100mm for installation in the shallow construction concrete slab but 300mm wide to provide generous water holding capacity .

Three of the curved drainage assemblies, providing over 85m of drainage at the top of the stairway, are based on a 220mm deep by 300mm wide overall module combining a 120mm high slotted drain with the 100mm reduced depth Supradrain. They have eight 600mm deep catch-pits to allow rodding of the channel, as well as sump units, with various sizes of outlet to connect into existing drains.

A 50m long curved and faceted drainage assembly was designed for the bottom of the stairway, again with eight catch-pits and sump unit.

Two other drainage runs were also designed for adjacent retail areas, both using the same 300mm wide and 220mm deep grating module.

Tree surrounds

Jones designed nine special, super-size Arborslot recessed tree surrounds measuring
2500mm by 2500mm overall and with a 50mm deep or 125mm deep recessed tray to suit
adjacent paviours.  James Millington of BDP said: “Recessed tree grids allow paving to run close to the tree, reducing ‘clutter’ on the floorscape and the potential hazards to users, while still allowing drainage to the tree for healthy growth.”

The grids provide a 688mm square aperture to accommodate a 200mm diameter tree trunk plus subsequent growth.

The two support beams required to carry these large span units – designed for B125 loadings - were engineered to leave a 1300mm space to give clearance for the 1200mm diameter root ball.

Due to its size, the Arborslot frame has been strengthened with extended backing plates for packing deep into the concrete tree pit to prevent rotation. Gussets along the outside of the frame provide extra reinforcement against frame distortion.

In one corner, a 439mm by 530mm removable sump cover has been provided with two lifting points for access to a 300mm by 300mm removable sump below.

In another, a 204mm by 204 hinged self-closing cover acts as a watering point to an embedded perforated flexible pipe providing irrigation around the tree root ball.

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