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Making buildings: Term contractor changes working landscape at Greenhill place

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Words:
Jan-Carlos Kucharek

William Haggard, of Carver Haggard, tells Jan-Carlos Kucharek about the limitations – and unexpected freedoms – of working under a term contractor, with the firm’s new public realm scheme in Harrow

What is the background to the project?

Harrow’s placemaking team is dynamic, and in addition to Section 106 levies in 2018 it applied the Mayor of London’s Good Growth Fund for funding to convert a town centre surface car park into a public square. The site was identified as being of strategic value as 500 units of housing are going up around it and it’s on a key pedestrian route. The quality of space and its ‘play’ aspect were important – the council was drawing lots of people into this urban centre and needed to make it more suitable for public use. Some council departments were worried about loss of parking and almost all our efforts at Stage 1 of the design were about allaying concerns, verifying actual demand or proving parking could be redistributed elsewhere in the borough. Now the site has been stopped up, with land transferred from Highways to Commercial Property departments. The square is leased to operator Tudor Markets and the Arts kiosk run by Harrow Arts Centre.

What were the contractual relationships that brought it about?

Councils procure highways and public realm works using a few, sizeable ‘term contractors’, usually for a five-year term. And because councils want price certainty, works such as fixing a pothole or installing a bollard or lamp post are priced on material rates rather than on a project basis. The term contractor has a list of products that it regularly uses and a schedule of associated rates. This might give price reassurance to councils but what’s good for a road is not necessarily good for a one-off public realm project. It can be a challenge to specify items that aren’t on the contractors list because if you do, they’re treated as specials. For us, the key aspect of working with a term contractor was that it was about fixed rate rather than fixed cost, meaning constantly monitoring any design changes.

Greenhill Place Market looking north – a public realm to support new housing.
Greenhill Place Market looking north – a public realm to support new housing. Credit: Francesco Russo

How did you manage to overcome the limitations of the contractors list?

We accepted that baseline public realm stuff  like level-setting, surface finishes and lighting would be done by the term contractor; but first we asked what it had left over in its yard that we might be able to use. It turned out to have some big slabs of granite over-ordered from another project – enough to make some bench seating and create granite steps leading up to the highway around the square. We also used pieces of leftover basalt for the kiosk dining area. Drainage kerbs and grilles were standard elements, as were the ‘power’ bollards, though we colour-matched these to go with the rest of the scheme. Pricing for supplying, cutting, delivering and installing the items on site was a little opaque, but the material itself was almost zero cost, and we’ve since done the same thing on another project.

How did you manage to include specific products not on its list?

We had to defer to the term contractor on the public realm works but we had a good relationship with Harrow’s Highways project manager and so were able to work in a few specials into the job – priced by suppliers so that the council was confident to order them in itself.

We had originally wanted quality paving for the square and so were surprised by the design review panel’s suggestion to use tarmac, but it really worked for the project. We conceded that using it was probably the best way to deal with all the level changes, avoiding unsightly cutting of stone on site which, in our consultant’s role, would have been out of our control to manage anyway. And cost savings on that perhaps left the panel more amenable to our other specials such as the terrazzo ‘welcome mat’ spelling out the name of the square. This was relatively costly but has civic quality, adding both colour and material delight to the project. Andrews Terrazzo cast it in Leeds, brought it down and laid it and we’re really happy with the result.

We also designed special steel cruciform bollards, made of four standard angles welded and painted by a Broxap and delivered to the council, with the contractor installing them at standard installation rates. We were worried we’d end up with standard play equipment from the list, but managed to get the council to agree to our designing it, with supplier PlayEquip matching the kiosk design aesthetic.

A key element for us was also bespoke cast cruciform brass pitch markers running at 3m centres on the site’s edge which, set into the tarmac and paving, are more subtle than we thought. Each has a unique grid reference marked on it to place it. We had to fight for them but feel it’s a small detail that creates extra nuance for the project and which we hope the public will discover through use.

  • Kiosks were built by Halo Structures under a D&B contract distinct from the landscaping one.
    Kiosks were built by Halo Structures under a D&B contract distinct from the landscaping one. Credit: Francesco Russo
  • The ‘welcome mat’ and art kiosk both announce the market square to shoppers on Station Rd.
    The ‘welcome mat’ and art kiosk both announce the market square to shoppers on Station Rd. Credit: Francesco Russo
  • Small brass markers set into the tarmac and paving denote pitch positions.
    Small brass markers set into the tarmac and paving denote pitch positions. Credit: Francesco Russo
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But you say the project was eventually procured under separate contracts?

Yes, two. The council and community stakeholders wanted to encourage local retail business. The GLA funding bid had included food kiosks around the square, although the council’s estates team raised concerns including security risk, so the original idea was that these would be off-the-peg units brought to site.

But we built a case to show that combining them into a single structure would create a more cohesive public space – in effect a market square. Because it was a very particular kind of ‘special’, this element was procured from a specialist fabricator.

So how did you eventually procure the kiosks?

Kiosk foundations were procured through the term contractor because it was civils work. We were uncomfortable with the amount of concrete it required –  even as pads it amounted to 130 tonnes. Luckily, with our engineer Toby MacLean, we and the term contractor agreed on helical steel coil foundations topped with a bolted, galvanised grid. A sustainability argument was won for sequencing and construction – it was simpler and required less in the way of earthworks, which were employed only for the attenuation tank that sits under the central play space.

We tendered the kiosk job publicly to find a specialist company able to do this work under design and build, to mitigate Harrow’s risk concerns. Halo Structures won the tender using its own lightweight steel structure of Meccano-like castellated beams which are screwed together on site and just as easily demounted for re-use at end-of-life.

The built structure is a simple shell and core – no fit-out – just a water and power supply for tenants. Aluminium shutters are installed over the kiosks and dining space to address security concerns. The collaboration with Halo was good and we really liked its system, so we exposed it where we could. Its laser cut steel structure with threaded fixings is visible through the grille soffit of our roof overhang. On this, Halo suggested that our frieze could be made using layered Tricoya MDF as a fascia plate, and it came out well. Although we had intended the outer columns to be structural, they became redundant with the Halo system, but we decided to keep them to retain a colonnade language.

In the end we missed out on some nice-to-haves, like getting green glass chips set in the tarmac to make it sparkle, and couldn’t get our desired kiosk lighting, but we came away from the experience surprisingly philosophical about it. It made us realise that had the whole project been procured as D&B, there would always have been a punitive aspect to design changes. Instead, working under the term contractor gave us in some ways more flexibility to make design changes as we saw fit; so that, with their support, we weren’t bound into one approach.

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