BENVGTC2 URBAN DESIGN: LAYOUT, DENSITY & TYPOLOGY
Analysis of density, typologies, and urban character in CA4 Hatton Garden Wing Sze Catherine Chao October 2017
CONTENT INTRODUCTION 3 SITE PLAN 4 TWIN TOWER - BABINGTON AND CHANCELLORS COURTS
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HYBRID - BOURNE ESTATE 6 KEY SPATIAL CHARACTERISTICS 7 VITALITY 8 QUALITY OF OPEN SPACE 9 QUALITY AND EASE OF MOVEMENT 10 REFLECTION 11 CONCLUSION 12 REFERENCE 13
INTRODUCTION Character Area 4 Hatton Garden lies within Holborn district of the London Borough of Camden. The area has a mix of building typologies that support primarily residential, retail and commercial uses. The outlined site located to the north of CA4 Hatton Garden is the controversial Mount Pleasant redevelopment site approved by former Mayor of London Boris Johnson. In face of widespread opposition, Mayor Sadiq Khan has decided to develop alternative schemes that pay regards to the existing buildings, urban character, and communities living in surrounding neighbourhoods. Hence the aim of the report is to help support the Mayor’s decision through examining the key spatial characteristics of urban typologies, and their relationship with the qualities of the urban environment and the way it is experienced. The report consists of a comparative analysis on the density, typologies, and character of two urban building types in CA4 Hatton Garden: 1) twin tower and 2) hybrid (courtyard block and rows).
Twin tower - Babington and Chancellors Courts Babington and Chancellors Courts locates in the west of CA4 Hatton Garden. They are two identical free-standing 14-storey postwar council buildings. The typology of the buildings is identified as a twin tower, which is contrasting to neighbouring buildings. Further, they exhibit unique configuration of open space; unlike the majority of buildings in the area where back gardens and courtyards are enclosed by buildings, Babington and Chancellors Courts stand in the centre of the site and are surrounded with open space. Their spatial character is outward-facing.
Methodology
Hybrid - Bourne Estate
Babington and Chancellors Courts, and Bourne Estate were chosen for the comparative analysis. Babington and Chancellors Courts are twin towers, whereas Bourne Estate is a composite of courtyard block and rows. Despite their distinct typologies, they also exhibit different building scale and location, land uses, use of open space, and accessibility, which in turn affect the character of the place and human experience.
Bourne Estate locates in the east of CA4 Hatton Garden. While it is a Grade II listed Edwardian estate primarily for residential uses, some of the building blocks with frontage facing Clerkenwell Road and Leather Lane also housed ground-floor retail shops and food establishments. Typology of Bourne Estate is made up of a uniform courtyard block as well as buildings laid out in parallel rows, which create a hybrid urban building type with inwardfacing spatial character.
Site visits were conducted on 7-Oct-2017 and 19-Oct-2017. The purpose of the site visits was to gain first-hand observations of the character of the built environment and experience on the social context and qualities of the local area. Various literature and government documents have also been taken into account in the analysis. The key spatial characteristics that differentiate the typologies are how the buildings define the streets, amount and use of open space, and locations and number of access points. These characteristics reflect impacts in the vitality around site area, quality of open space, and quality and ease of movement.
Figure 3. Map of London
Figure 4. Hatton Garden CA4
Figure 1. Babington and Chancellors Courts
Figure 2. Bourne Estate
Figure 5. Figure-ground map of Hatton Garden
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SITE PLAN
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Figure 6. 1 : 4000 site plan of CA4 Hatton Garden
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TWIN TOWER - BABINGTON AND CHANCELLORS COURTS The twin tower contains 112 dwelling units. It comprises two 14-storey residential buildings and on each floor there are 4 dwelling units. There is only one north-east facing entrance on each of the twin tower. The total site area is 12,881m2 and the total floor area is 10,772m2. A high proportion of the site is open space and is managed by the Camden Council.
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The parking space is for private parking only, mainly provided for the residence of the twin tower. It is managed by the Camden Council and an estate parking permit is required. Residents have direct access to the parking space from the open space, and vehicles can enter from New North Street. There are no physical barriers at both the entrance of the parking space and the main entrance to the site from Orde Hall Street, which means everyone has free access to the site. Although on the map it may appear to have free access to the green space, access is not encouraged due to the presence of railings around the green space. Also, while the playground is located next to a public street (Figure 9), it is enclosed by taller railings and a gate that is facing inwards towards the buildings, which suggests that it is for residence use only.
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Figure 7. 1 : 1250 schematic plan of twin tower
Figure 8. Paved area around twin tower
Plot coverage
Floor area ratio (FAR)
Number of dwellings
Figure 9. Playground next to twin tower
Figure 10. Birdeye view of the twin tower (Google Earth Pro a, 2017)
Dwelling density/hactare (net density)
Tower buildings often associates with high density, however despite being at least twice as tall as the courtyard blocks in the hybrid, the twin tower has lower dwelling density per hectare than the hybrid. This could be because the twin tower is built at a small scale, covering only 12.71% of total site area, and a lower FAR. According to Alexander (1977), use of land can be optimised and a continuous urban fabric can be formed by building no more than 50% of the total site area. Whilst the twin tower has not exceeded the suggested limit, it failed in maintaining at the predominant height as the surrounding buildings, hence creating an over-scaled built form that disturbed the continuity in built form within the neighbourhood.
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Figure 11. Cross-section of twin tower (A - A’)
36m Paved area
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HYBRID - BOURNE ESTATE The hybrid contains 315 dwelling units. It consists 6-storey buildings that formed a courtyard block with perimeter along Clerkenwell Road, Leather Lane and Portpool Lane, and six parallel 5-storey buildings laid out in rows within the courtyard block (Figure 14). There are multiple entrances to the buildings. The total site area is 12,880m2 and the total floor area is 33,394m2. Compared to the twin tower, the hybrid has relatively lower proportion of open space, which is also managed by the Camden Council. Whist the open space is enclosed by the hybrid buildings, it is accessible for all through the main archway entrance at the north-east of the site.
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With respect to Bourne Estate’s historical and architectural significance, the Camden Council devised a redevelopment scheme for the estate buildings in 2013. The scheme includes 75 new housing units with a mixture of private sales, shared ownership and council housing units (Camden Council, no date). Whilst the hybrid exhibits relatively less open space, unlike the open space in the twin tower site, detailed designed landscaping that complements the architectural character of the buildings has been applied to the green space and paved area in the courtyard of the hybrid (Figure 13). The hybrid also has relatively more trees, shrubs, and garden beds.
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Figure 12. 1 : 1250 schematic plan of hybrid
Figure 13. Courtyard of hybrid
Plot coverage
Floor area ratio (FAR)
Number of dwellings
Figure 14. Rows of buildings within the courtyard
Figure 15. Birdeye view of hybrid (Google Earth Pro, 2017b)
Dwelling density/hactare (net density)
It is suggested that with the combination of city blocks, courtyard blocks can increase building density and optimise the use of land (Bürklin, 2007). In the case of the hybrid, the courtyard block is combined with one / two-sided rows. It demonstrates higher percentage of plot coverage and FAR than the twin tower.
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Figure 16. Cross section of hybrid (A - A’)
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KEY SPATIAL CHARACTERISTICS Defining of streets
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Figure 17. Street edges created by the buildings The typology and position of buildings within the site can influence on how streets are delineated. For instance, the twin tower is two independent blocks that does not form a perimeter around or along the streets. Also, the twin tower is positioned in the centre of the site at a distance from the streets, given that it is constructed at a relatively smaller scale with low plot coverage, this would mean it is not possible to form an adjacent edge that defines the streets. In contrast, the courtyard block in the hybrid are a series of adjoining buildings that run at the periphery of the site and along the streets. Not only does it confine the space within the courtyard, its outward facing side also serves as a consistent street edge that creates well-defined streets and continuity in the building fronts.
Figure 18. Amount and shape of open space In relation to the total area of the site, open space takes up 87% of the twin tower site and 51% of the hybrid site. Open space in twin tower exhibits irregular shape and is bounded by the site boundary rather than the buildings. On the contrary, the shape of open space in hybrid is uniformed and confined by the courtyard block. The shape and size of open space can influence the functional relevance and quality of the surrounding area. Further analysis on the diversity in use, shape, and scale and enclosure of the sites is presented in the QUALITY OF OPEN SPACE section (page 9).
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Figure 19. Access points of the site and the buildings Access points presented in this report refer to 1) point of entry to the site, and 2) entrances into buildings. There are multiple points of entrance to the twin tower site and only one entrance to each of the two buildings, while the hybrid site shows the opposite. Access to the buildings in hybrid are mostly located in the courtyard, which means people have to pass through the same site entrance regardless of which building they head to. Hybrid offers site access points at three of the four sides of the site, with the appropriate open space setting, flexible choices of route from different direction can be generated. Access and barriers, and permeability of the site and its buildings are significance to the QUALITY AND EASE OF MOVEMENT, which is examined in page 10.
Building typologies and layouts that can establish well-defined streets can be one of the factors contributing to the vitality of the surrounding area. The VITALITY section (page 8) examines land use and active frontages, and how they influence the vitality of the neighbourhood.
Figure 20 & 21. Open space in twin tower (left) and hybrid (right)
Figure 22 & 23. Entrance to twin tower from Orde Hall Street (left) (Google Map, 2017a) and entrance to hybrid courtyard (right)
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VITALITY Both buildings in twin tower are dedicated to residential land use, whereas buildings in hybrid has a mixed use of residential, retail and food establishment. While it would be more challenging for single-use twin tower to establish strong vitality, effort has been made to create a more convivial environment by expanding the variety of use in the open space through soft landscaping and the presence of the playground. Entrances to the residential units in hybrid are located inward of the courtyard block, this has provided opportunities for non-residential uses at the building front to create streets that are usable and can induce social activities (Alexander, 1977). The six parallel rows of buildings in the courtyard and the south-facing side of the courtyard block are purely for residential use only. The north and east-facing side of the courtyard block have residential units above and commercial units on the ground floor facing Clerkenwell Street and Leather Lane, housing a total of 22 retailers and food establishments. This has created an active frontage along the 2 main streets in CA4 Hatton Garden that forms interactive street edges and encourages adaptive use of old buildings (Figure 26). Residential use
Retail use & food establishment
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Adding to the street activity in the surrounding area is the Leather Lane Market which is located directly next to the hybrid. It fosters a unique character and great sense of community where hustling street markets can coexisted with habited residential units in the courtyard block (Figure 24 & 25).
22 Figure 24. Leather Lane Market (ilovemarkets, no date)
Figure 25. Food stall in Leather Lane Market (Yaya, 2015)
Figure 26. Elevation of ground-floor retail shops and food establishments of courtyard block in hybrid (facing Clerkenwell Road) (Google Map, 2017b)
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QUALITY OF OPEN SPACE 13.0%
48.5%
Twin tower
Twin tower comprises greater variety than hybrid. However this does not imply that twin tower demonstrates better utilisation of space. Rather, most of its paved area and green space lacked amenity that could draw people to the space, encourage dwell time, and induce social behaviours (Figure 27). Paved area and green space in hybrid are purposefully designed to create paths, nodes and soft edges. There are greater variety of plants, and forms and appearance of raised garden beds that can also be used as places of sitting (Figure 30). While my two site visits and limited time for ethnographic observation may not be comprehensive enough to form a conclusion of whether twin tower or hybrid has prompt diverse and wider extent of social activities and behaviour, it is in theory that places like hybrid with greater variety, richness and good sitting opportunities possess favourable conditions to create responsive and better quality of outdoor environment (Gehl, 2006; Bentley et al., 1985).
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According to Alexander (1977) positive outdoor space has “distinct and definite shape…and when its shape is as important as the shapes of the buildings which surrounds it” (p.518), whereas negative outdoor space is shapeless. Positive and negative outdoor space can also be defined by the degree of enclosure. Open space in twin tower is irregular in shape and is not defined by the buildings, but rather by intentionally built fences and walls of surrounding buildings, suggesting a negative outdoor space. Open space in hybrid demonstrates positive outdoor space where its shape is uniformly defined by the courtyard block, it acts as a spatial constriction that differentiates areas within the site and public street space beyond the courtyard block (Bürklin, 2007).
Public / private / semi-private? • Public open space – urban space, designated by a council, where public access may or may not be formally established, but which fulfils or can fulfil a recreational or non-recreational role (Planning Portal, no date a, no page)
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• Private open space – open space that is usually privately owned and is not usually accessible by members of the public (Planning Portal, no date b, no page)
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Figure 27. Underuse open space in twin tower
• Semi-private open space – include those where a limited number of people use the space but where the ordinary public would generally not be welcomed, and spaces generally accessed and be used by particular groups within society (Woolley, 2012, p.4) By definition, open space in twin tower is public. Exception is the playground where it is a semi-private open space because while there is no official restriction of entry, it is surrounded by tall railings and a gate that are facing inwards towards the buildings, which suggests that public use would not be welcomed.
Figure 28. Parking space in twin tower
Figure 29. Paved area between rows of buildings in the hybrid
Open space in hybrid is entirely public, but it may not be apparent to the public who are not familiar with the neighbourhood due to its lack of permeability. It is proposed that enhancement work for strengthening the potential of public space within the Bourne Estate is needed (Camden Council, 2016)
Figure 30. Green space in the hybrid
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The building height to open space width ratio for twin tower in 1 : 1.24, and 1 : 1.13 for the hybrid. It is suggested that open space with strong sense of enclosure can be created with a height/width ratio of 1:2 or 1:3 (LaGro, 2011). Despite an out-of-range height/width ratio for hybrid, the sense of enclosure created by courtyard block itself is sufficient to give people feeling of comfort and security (Alexander, 1977), but this may not always be true since perception of comfort and safety is subjective, it can be affected by physical and social factors such as orientation and lighting, and types of dominating users of the open space. Same applies to twin tower where some people may prefer spacious, unconfined open space.
Figure 31. building height/open space width ratio of twin tower (left) and the hybrid (right)
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QUALITY AND EASE OF MOVEMENT Permeability t
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Figure 32. Pedestrian and vehicle permeability
Figure 33. Flow of active pedestrians on adjacent streets
Figure 34. Types of barriers and points of access
Twin tower exhibits higher permeability across the site with more flexible choices of pedestrian routes, while pedestrian routes in hybrid are constricted by the only entrance to the site and the rows of buildings in the courtyard. Unlike twin tower that has designated parking space, vehicles and pedestrians have to share the same route and space which could hinder pedestriansâ&#x20AC;&#x2122; use and experience of space.
Street along the north frontage of hybrid has higher pedestrian movement since it is one of the main road in CA4 Hatton Garden and also due to the presence of active ground-floor frontage along the courtyard block.
Given that twin tower is unable to form a boundary around its site, barrier such as fences, walls, and gates are used to mark the periphery around the open space. Barriers play less role in the hybrid site due to the nature of typology as a courtyard block. However, possible entrances to the hybrid site are gated, leaving only one site entrance at the north-east of the site and limiting the permeability and choice of movement.
Pedestrian movement is distinctively lower on streets surrounding twin tower due to its distance to the main road. However, unlike hybrid where majority of movement concentrate at the periphery of the buildings, pedestrians were seen to go from one street to another by cutting through the site as a shortcut. This also highlights the high permeability of twin tower.
Railings in both sites restricted the use and access of green space, and the playground in twin tower is limited to a particular group of users i.e. residence of the twin tower buildings.
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REFLECTION Density may be a useful tool to help describe, project and manage the use of land, however it can often be a misleading indicator when it is not clearly defined. For instance, dwelling density per hectare can be measured as net density or gross density. Results can vary differently depending on whether or not variables of the wider urban space context are included into the calculation. In one of the tutorial sessions, I was told that my calculations for dwelling density per hectare was wrong because I had different sets of results than those who have the same site as mine. It turns out that our method of calculation was correct, but what we included into the total site area was different. One should not make assumption that a particular urban built typology can always create high urban densities without fail (e.g. tower, solitaire, high rise buildings). As seen in the case of the twin tower and the hybrid, whilst being at least two times as tall as the hybrid, the twin tower exhibits lower dwelling density per hectare. This could be due to low plot coverage and floor area ratio. Measurement of dwelling density should not be used alone, but rather multi-variable density models should be adopted (Boyko and Cooper, 2011). One example is the development of the Spacematrix model (Pafka, 2013). There can never be an “ideal” urban built typology. Whether or not a particular type of building works well in the urban fabric differs across cities and is highly dependent on the other elements of the built environment, (e.g. open space, street network, and natural landscape). It is stated that “typological thinking can be useful for urban design but types are inevitably simplifications of very complex assemblages” (Dovey, 2016, p.78). Built typologies have to adapt to the social and economic context of the area so as to recognise and fulfill local needs. As seen in the case of the hybrid, the combination of courtyard block and rows has morphed into a new type that forms unique spatial configuration that possess different qualities of the urban environment and user experience. 11
CONCLUSION
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Defining of streets
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Plot coverage: 12.71% Floor area ratio: 1.74 DPH:180.50
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• The typology and position of buildings can influence on how streets are defined • Free standing tower blocks that are in the centre of an area is unlikely to form street edge • Courtyard blocks that run at the periphery of site create welldefined streets and uniformed building fronts
• With the appropriate open space settings, single-use buildings can induce social interactions • Active frontage can be a form of interactive street edge that creates unique street characcter
• Quality of open space is not only determined by size but also shape and diversity of use • People are more likely to move • Sense of enclosure can be freely and have more choices of monitored and controlled by routes when open space is not following rules of height/width restricted by uniformed boundary ratio, but it can also be influenced and structures by subjective views on the physical and social conditions of the site
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Plot coverage: 48.83 Floor area ratio: 2.59 DPH: 244.55
• Barriers have to be purposefully installed to mark the boundary of the site if the building and its typology is unable to do so
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REFERENCE Alexander, C. (1977) A Pattern Language: Towns, Buildings, Construction, New York: Oxford University Press Bentley, I., Alcock, A., Murrain, P., McGlynn, S. and Smith, G. (1985) Responsive Environments: A Manual for Designers, London: Architectural Press Boyko, C. and Cooper, R. (2011) Clarifying and re-conceptualising density, Progress in Planning, 76, p.1-61 Bürklin, T. (2007) Basics Urban Building Blocks, Boston, MA: Birkhäuser GmbH Camden Council (no date) Bourne Estate regeneration. Retrieved from https://www.camden.gov.uk/ccm/content/environment/planning-and-built-environment/two/placeshaping/bourne-estate-regeneration/ [accessed 20 October 2017] Camden Council (2016) Hatton Garden Conservation Area – Appraisal and Management Strategy Consultation Draft. Retrieved from https://consultations.wearecamden.org/culture-environment/hatton-garden-conservation-area-appraisal-and-mana/supporting_documents/Hatton%20Garden%20Conservation%20Area%20Appraisal%20 and%20Management%20Strategy_nov%202016B.pdf [accessed 17 October 2017] Dovey, Kim (2016) Urban Design Thinking - A Conceptual Toolkit, London: Bloomsbury Gehl, J. (2006) Life Between Buildings: Using Public Space, Copenhagen: Danish Architectural Press Google Earth Pro (2017a) Babington and Chancellors Courts 51°31’17.32”N, 0°07’12.54”W, elevation 66ft [accessed 20 October 2017] Google Earth Pro (2017b) Bourne Estate 51°31’17.11”N, 0°06’41.12”W, elevation 98ft [accessed 20 October 2017] Google Map (2017a) Entrance to Babington and Chancellors Courts. Retrieved from https://www.google.co.uk/ maps/ [accessed 20 October 2017] Google Map (2017b) Clerkenwell Road. Retrieved from https://www.google.co.uk/maps/ [accessed 20 October 2017] ilovemarkets (no date) Leather Lane Market. Retrieved from http://ilovemarkets.co.uk/listing/leather-lane-market/ [accessed 24 October 2017] LaGro, J.A. (2011) Site Analysis : A Contextual Approach to Sustainable Land Planning and Site Design, New York: John Wiley & Sons Pafka, E. 2(013) Nothing Gained by only Counting Dwellings per Hectare: A hundred years of confusing urban densities, State of Australian Cities Conference, Sidney Planning Portal (no date a) Glossary – Public Open Space. Retrieved from https://www.planningportal.co.uk/directory_record/454/public_open_space [accessed 17 October 2017] Planning Portal (no date b) Glossary – Private Open Space. Retrieved from https://www.planningportal.co.uk/directory_record/450/private_open_space [accessed 17 October 2017] Woolley, H. (2012) Urban Open Spaces, London: Routledge Yaya (2015) Food stall on Leather Lane Market. Retrieved from https://handluggageonly.co.uk/2015/05/20/14amazing-street-food-markets-you-have-to-visit-in-london/ [accessed 24 October 2017]
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