We spent two weeks looking at the building, studying it and learning from Phase 1. We noticed the remnants of lives lived there, the traces of inhabitation and how residents had made their flats homes. Some had painted their balcony cheeks different colours, all had laid patterned linoleum on their doorsteps. We won the competition with our proposal: to faithfully restore the building keeping as much of the existing fabric as possible, upgrading it thermally and acoustically, and giving each flat its own identity using patterned doormats and coloured balcony reveals.
It was another milestone in the life of a scheme that has remained one of the lodestars of UK post-war housing since being built and a bellwether of attitudes to them.
Mikhail Riches’ sensitive picking up on and referencing of clues offered by the existing fabric has been a feature of its nuanced approach throughout the project.
Internally, rooms have been lined like ‘insulated boxes’– with insulation added to the cavity wall brick panels, windows moved back into thermal line and balcony flank walls and the soffits of living spaces all lined in insulation. The latter, while aiding with acoustic separation and providing a concealed service zone, also results in an unfortunate squeezing of head height, given the already low floor-to-floor dimensions of 2.515m, to just 2.215m.
Repair mortar and an anti-carbonation coating was applied to all exposed concrete elements. The aim of this coating was to provide a barrier to mitigate further carbonation and extend the design life of the superstructure frame.
Park Hill is an exposed concrete frame building. Its Grade II*-listed status means that overcladding the concrete, which acts as a massive cold bridge, was not an option; we needed to insulate both sides of the concrete in each room.
Completed in 1961 by Sheffield City Council, Park Hill is a Grade II*-listed Brutalist housing scheme, containing 1,000 homes, making it Europe’s largest listed structure. Urban Splash took on its redevelopment and Phases 1, 2 and 3 are now complete.
Civic Engineers acted as civil and structural engineer on Park Hill Phase 2 for Urban Splash. Having provided the same service and support on Phase 1 (2007-2011) and Phase 3 (2017-2020), Phase 2 saw our role evolve as we designed a retentionist repair strategy for the existing concrete frame. The principal design aims of this were:
- To prolong the useful design life of the concrete frame
- To do so in a way that would not permanently damage its heritage importance, which was also in keeping with the proposed façade treatment
- To do so in a way that would provide a durable exterior to gain approval from building warrantee providers
- To maximise the period to first maintenance.
The brickwork has been lightly cleaned externally and insulated internally. New windows are pushed back to the thermal line with pressed aluminium reveals creating depth to the façade, providing some solar shading while giving the brick an equivalent treatment to Phase 1’s brightly coloured panels.
Alim Saleh, senior architect, Mikhail Riches
The only major demolition of the frame has been around the entrance areas, where new double-height lobbies have been created through the removal of flat units. The treatment of these lobbies is much rawer than in Phase 1. There, elements like a shiny sculptural stainless-steel stair were inserted; here, lifts and stairs remain strictly orthogonal and utilitarian, with existing concrete walls left showing all their history, including the cast-in timber chocks used to attach skirtings in the lost flat units.
The listing, while saving the building, threw up extra issues for retrofitting it and making it financially viable for a developer to take it on. Given this, it was agreed, after discussions with English Heritage, that for Phase 1, Urban Splash could strip the structure back to the frame and rebuild from there. The bright-hued ‘look-at-me’ transformation was the result, with the pinkish and buff brick infill panels replaced by powder-coated aluminium. In addition, the previous balance between window and solid wall was inverted, significantly increasing the proportion of glazing on the façade.
Gobsmackingly, it was just one of four huge estates – and not even the largest – planned and built in a ring around Sheffield by Womersley’s team. However, as with many other large Modernist estates in the UK and against a background of deindustrialisation and rising unemployment in the 1970s and 80s, all four estates suffered from lack of maintenance and antisocial behaviour. By the following decade, the other three had been totally or partially demolished. It’s a fate Park Hill might have suffered too but for its Grade II*-listing in 1998, in recognition of its importance as a fully realised version of ‘streets-in the-sky’ and its inspired use of its hillside site.
Source:Left: Keith Collie, right: Daniel Hopkinson
We are also working with low existing ceiling heights: floor-to-floor dimensions are 2,515mm (these would be at least 3,100mm in a modern building) but to achieve the best results thermally within the tight parameters we have added insulation to bring ceiling heights to 2,215mm.
Historic photograph of Park Hill Flats by Sheffield City Architect’s Department, 1961
Architect’s view
‘It’s also incredibly complex – more like a 3D jigsaw puzzle. That meant every corner has had to have a bespoke solution to the wet-cold frame. It would have been so much easier just to overclad it!’
But the completion of Phase 1 undoubtedly remains a signature model for the reimagining and rehabilitation of Modernist estates, both as places to live and in the public imagination. It was shortlisted for the 2013 Stirling Prize at a time when the demolition of other prominent examples, such as London’s Heygate Estate, was gathering pace.
This report was crucial for our performance specification and repair strategy which included removing areas of defective concrete, including cleaning and removal of corroded reinforcement. Where corrosion of exposed reinforcement was significant, bars were locally cut out and replaced with new welded reinforcing bar primed for application of repair mortar.
In 2015 Urban Splash held a competition for Phase 2 of the project: 195 flats and 2,000m2 of commercial space. It gave the five shortlisted practices a flat in the derelict building and two weeks to demonstrate their ideas. The brief asked the architects to ‘spend as much time on the site, live and breathe it, wholeheartedly commit – can you do this?’
‘We noticed how many people had painted their balconies,’ says founding director Annalie Riches, pointing to the range of hues the practice chose to paint the flank-walls of each balcony. ‘We wanted someone to be able to point at the block and say that turquoise one is my flat.’
While the scheme still contains some three-bed units, usually at atypical, cranked knuckle points in the plan, it feels as though the demographic encouraged and expected here is more couples than families.
Internally, the tight layout of each flat has been eased by converting most three-bed units to two-bed with an added en-suite. The sense of openness has also been increased by removing walls between stairs and landings. The wall finishes wrapping around the stairs are nicely left as raw concrete – it being far enough away from the external envelope for insulation to offer only limited thermal benefit.
The past decade has seen the focus on reducing embodied carbon shift the approach of retrofit to maximum retention of fabric. Indeed, the choice of Mikhail Riches – a practice known for its fabric-first, materials-based work – was perhaps itself reflective of this changed thinking. In the final round of the 2015 competition, when each shortlisted practice was given an empty flat to work with for the final interview, rather than attempting a temporary wasteful fit-out, the practice illustrated its concept simply and economically with drawn sketches on the room walls. Looking appropriately like 50s magazine illustrations, these incorporated patterns and cartoons from the fragments of remaining wallpaper into the design. ‘We felt from the beginning that they really understood the DNA of the block,’ says Latham.
The scope of other future elements remains under question. The S1 artist-led gallery space and studios planned for Phase 4, won in competition by Carmody Groarke in 2017, is still seeking more funding.
It was one of the earliest and most complete manifestations of the ‘streets-in-the-sky’ concept first mooted by the Smithsons in their 1952 Golden Lane Estate competition entry – itself channelling Le Corbusier’s original Unité in Marseilles. The basic model was of mega-blocks or estates functioning as self-contained neighbourhoods, with dwellings accessed off supposedly street-like pedestrian walkways, separated from vehicular traffic.
More successfully, glazed slots with built-in shelves have been cut next to front doors, allowing better light and overlooking and also a chance to display objects as a marker personalising each entrance – a feature inspired by the corner display windows incorporated into the entrances of Phase 1.
Phase 1 by Studio Egret West and HawkinsBrown
The works to the concrete frame created a robust and durable exterior allowing safe reoccupation of the structure.
Dan Podesta, associate, Civic Engineers
‘We wanted it to be visibly transformed,’ said Urban Splash development manager Mark Latham at the time of this initial zingy regeneration of 260 of the almost 1,000 flats in the Modernist estate, originally completed in 1961 to designs by Ivor Smith and Jack Lynn, which sits prominently on a hilltop to the east of Sheffield’s city centre. ‘It was important for making people realise what it could be.’
One can’t but help read a slightly bish-bash-bosh noughties optimism in the first phase compared with Mikhail Riches’ more subdued and subtle rework, slightly austerity-Britain
This was Rory Olcayto in the AJ in 2013 describing the vivid visual hit of anodised aluminium panels used by HawkinsBrown and Studio Egret West in the first phase of Park Hill’s retrofit for Urban Splash.
In any case, the steer from English Heritage – after the more billboard nature of Phase 1 – was that this phase should retain more of the original fabric in light of the estate’s listing. Another factor was the knowledge that, whereas the enormous amount of spoil from Phase 1 was reused to form the landscaping, any demolished fabric from later phases would have to be expensively removed from the site.