Cressingham Gardens Tulse Hill, London Residential Conversion

Cressingham Gardens Tulse Hill, London

Residential Conversion Feasibility Report - Draft

February 2016

For the London Borough of Lambeth Produced by Tibbalds with GSA

Confidential Tibbalds Planning and Urban Design 19 Maltings Place 169 Tower Bridge Road London SE1 3JB

Telephone 020 7089 2121 [email protected] www.tibbalds.co.uk

Cressingham Gardens ❚❚Contents

1.0 Introduction

2.0 Description of the Existing Buildings

3.0 Residential Quality

4.0 General Considerations

5.0 Block Specific Considerations

6.0 Typical Block Study

7.0 Strategic Sitewide Considerations

8.0 Example Projects

9.0 Summary

©Tibbalds Month 2016 Cressingham Gardens Residential Conversion Feasibility 1 ❚ 1.0 Introduction

The estate was designed in 1969, since that time some aspects of the housing estate have worked well, but there have also been issues. As a result London Borough of Lambeth are currently considering the future of the estate, and ways in which the area can be regenerated.

There is some opposition from the local residents’ group to regeneration options that would involve demolition of the existing housing stock. Despite some negative issues (such as break-ins to the basement parking, problems with drainage and foul water leakages in the garages – to name a few), the estate appears to be popular. It is well kept and appeared to be relatively safe (despite its less than conventional layout). The residents have put together an alternative Peoples Plan for the future of the estate that does not involve demolition – involving the conversion of basement / undercroft parking to residential use.

This report is preliminary investigation of the design issues that would be raised by such a conversion programme.

This report focuses on testing ideas for the residential Schematic drawing showing Hardel Walk conversion of four garage areas within the estate as shown (diagram from ‘Tulse Hill’ document by opposite. London Borough of Lambeth - Jan 1969)

Existing Section (showing Hardel Walk)

Cressingham Gardens Residential Conversion Feasibility ©TIBBALDS FEBRUARY2016 2 ❚ 1.0 Introduction

Location Plan showing the four blocks with basement car parking

©TIBBALDS MONTH 2016 Cressingham Gardens Residential Conversion Feasibility 3 ❚ 2.0 Description of the Existing Buildings

This study looks at four apartment buildings:

■■ Hardel Walk;

■■ The adjacent block we are referring to in this report as Hardel Walk South;

■■ Longford Walk;

■■ Crosby Walk.

The building form is broadly similar for all four blocks, however there are site speciﬁc issues relating to each block which will be described later in this report. Each block has a communal undercroft or semi-basement car park.

The structure visible within the basement is a concrete Crosby Walk frame. The downstand beams are of varying depths, with a deeper beam occurring every two bays.

Within each basement the general arrangement includes garages along the southern edge (western edge of Hardell Walk) and open parking areas along the northern side (or east for Hardell Walk) with railings onto the adjacent road, path or external space. Each of the basement areas gets light from one side only.

Access to the basement parking areas is generally from either end via electric gates. Often this access is ramped.

Each of the garage areas is set back behind an overhang of the residential accommodation above.

Longford Walk

Hardel Walk Hardel Walk South

Cressingham Gardens Residential Conversion Feasibility ©TIBBALDS FEBRUARY2016 4 ❚ 3.0 Residential Quality

The London Residential Design guide has been developed London Design Guide 5.4.1 requirement for 2.5m min to ensure that all new housing in London is of a good quality. floor to ceiling height in habitable rooms (ideally higher The guidance promotes residential accommodation that in ground floor homes). is robust and appropriate for use by people throughout The current floor to ceiling height is generally low (it varies, their whole lifetime (Lifetime Homes). It also should be but on average it is about 2.3m to underside of the concrete sustainable and allow people to lead a good quality of life. slab). The existing buildings all have a concrete structure The Peoples Plan suggests that the proposed dwellings with downstand beams of various depths which are even would be affordable tenures. It is worth noting that in lower (in some instances only about 1.8m clear beneath the addition to the London Residential Design Guide, affordable beams). homes will be expected to comply to further design ■■ Lowering the ground floor slab would require a structural and performance criteria (often associated with funding review (for impact on foundations). This might require arrangements), such as Housing Quality Indicators (HQI). expensive underpinning. These criteria are in place to ensure that the design of homes take into account how people want to use their home and ■■ Consider how services (including existing services their surroundings, now and in the future. to / from existing flats above) and ventilation is accommodated within the ceiling zone. This will impact Any new proposed housing within the London Borough of on the floor to ceiling height Lambeth would be expected to comply with the guidance within the London Residential Design Guide. The prospect ■■ Possible requirement for insulation at ceiling level. of converting basement car parking to residential at ■■ Possibly request a dispensation regarding floor to ceiling Cressingham Gardens raises the following issues regarding height, particularly where downstand beams would occur the quality of the resulting residential accommodation. The within the new flats. items listed below are not exhaustive, but represent the key issues that might have implications for cost planning and the delivery of the proposal.

Longford Walk - showing the low ﬂoor to ceiling heights Design proposals suggest lowering the ground ﬂoor slab

©TIBBALDS MONTH 2016 Cressingham Gardens Residential Conversion Feasibility 5 ❚ 3.0 Residential Quality

London Design Guide 5.5.1 Daylighting London Design Guide 3.1.3 Level access into the home.

Getting adequate daylighting into ground floor flats would This would require the external landscape scheme to provide be challenging, particularly getting adequate light levels a very gently sloping or flat pathway to the new front doors. into kitchens and living rooms. The following considerations There are a couple of options for accessing the front doors of could help: the proposed dwellings - either from a communal corridor at ■■ Design facades with generous amount of glazing. the rear of the flats, or giving each dwelling its own front door directly from the public realm. ■■ Locate the façade to align with the building face above (not set back from it) The greatest challenge to achieving this would be at Hardel Walk where the existing ground level noticeably slopes in a ■■ Don’t make the habitable rooms too deep. north – south direction. The floor slab of the car park is also ■■ Place bathrooms and storage at the backs of the flats / sloping here. maximise habitbale accommodation next to the facade, ■■ Consideration must be giving for achieving access for the where there is more light. disabled.

Existing Section- undercroft does not recieve much daylight Hardel Walk - the change in level between garage ﬂoor and outside

Cressingham Gardens Residential Conversion Feasibility ©TIBBALDS FEBRUARY2016 6 ❚ 3.0 Residential Quality

London Design Guide 4.10 - Requirement for all homes London Design Guide 5.2.1 requirement to avoid north to have private amenity space. facing single aspect dwellings.

The minimum width of private amenity provision is 1.5m. 3 of the 4 blocks (Longford Walk, Crosby Walk & Hardel This could be achieved by the provision of private patio Walk South) would have predominantly north facing aspect space or small gardens outside the existing buildings. (resulting in primarily north facing single aspect dwellings). This would require localized external works schemes – of ■■ Consider use of bay windows. The design of which could varying degrees of complexity – according to particular site ﬁt beneath the existing projecting oriel windows above. conditions. ■■ Or even a projecting extension with roof glazing (like a The Hardel Walk block would present the greatest conservatory). challenges, because of the considerable change in level between the car park ﬂoor and the external access. This could result in the loss of further existing parking spaces.

Localised landscape works would be required. This would result in a net loss of communal open space (communal open space being converted to private amenity space). However a mitigating factor could be the proximity of high quality public open space in Brockwell Park.

Crib wall precedent Projecting extension with roof glazing precedent

©TIBBALDS MONTH 2016 Cressingham Gardens Residential Conversion Feasibility 7 ❚ 4.0 General Considerations

There are other general issues that are common to all blocks.

■■ The car park areas are deep plan and generally single aspect. The rear space would not receive adequate daylighting for residential use. Perhaps these areas could be used for lock-up storage, bike stores or refuse stores (if effective ventilation can be achieved).

■■ An option could be looked at to retain the rear part of the basement as parking (requiring at least 11m for a 5m space and 6m reversing zone), with just the front part converted to residential (approximately 5m deep). Hardel Walk - existing gas pipe

■■ Drainage from upper ﬂoors come down into the basement. Some pipes appear to be rainwater, others appear to be foul water. Where the pipes enter the basement form above, it is likely that a rodding point (for access to the pipework) would be needed. This should ideally be located outside the demise of the dwelling.

■■ Other services are routed through the basements (there is a noticeable gas pipe in the Hardel Walk basement). This would require the gas supply to the ﬂats above to be re-routed.

■■ There are noticeable manholes in the floor surface of some areas of the car parks. This suggests that services run beneath the floor slab. If the internal floor level needed to be lowered to achieve sufficient floor to ceiling heights, this would need to be re-routed. Hardel Walk South - services coming down from the flats above

■■ There may be issues to do with sound transmission from above that would need to be checked.

■■ Consideration of energy performance (especially cold bridging) will also be important. There is likely to be a need for insulation below any residential accommodation at ground ﬂoor.

Hardel Walk - services coming down from the ﬂats above

Cressingham Gardens Residential Conversion Feasibility ©TIBBALDS FEBRUARY2016 8 ❚ 5.0 Block Seciﬁc Considerations

Although all the apartment blocks bear similarities to each other, the site conditions and context for each block is different. Here are some of the block speciﬁc observations:

Hardel Walk South (connected to the main part of Hardel Walk)

■■ Pro - has an existing light well, that might be incorporated into the residential design.

■■ Pro - the relationship of the car park ﬂoor slab to the existing external levels work better the rest of Hardel Walk block basement.

■■ Pro - the aspect to the north is pleasant looking out onto a public space.

■■ Con - some parts of the car park are an internal corner and therefore have no aspect so could not be converted Hardel Walk South- constraints and opportunities to residential space.

■■ Con - the aspect is north facing.

■■ Con - ﬂoor to ceiling heights are low.

Existing Section

©TIBBALDS MONTH 2016 Cressingham Gardens Residential Conversion Feasibility 9 ❚ 5.0 Block Seciﬁc Considerations

Hardel Walk (the largest of the blocks)

■■ Pro - has some of the highest ﬂoor to ceiling heights (due to a sloping ﬂoor slab) although these do vary considerably.

■■ Pro - has west facing aspect.

■■ Con - the external level is much higher than the internal ﬂoor slab (estimated to be 1.2-1.5m difference in some places). This could be overcome by lowering the external ground level, but that in itself raises other issues: - Major external works. This could involve retaining walls (parallel to Tulse Hill) in some places. - Existing Pedestrian accesses up to the’ internal street’ of Hardel Walk. At the moment it is easy going steps, these would become much steeper, or would need to be closed off. - Possible impact on signiﬁcant existing mature trees (especially plane trees) next to Tulse Hill.

Hardel Walk - constraints and opportunities

Existing Section

Cressingham Gardens Residential Conversion Feasibility ©TIBBALDS FEBRUARY2016 10 ❚ 5.0 Block Seciﬁc Considerations

Longford Walk Crosby Walk

■■ Pro - the relationship of the car park ﬂoor slab to the ■■ Pro - the relationship of the car park ﬂoor slab to the existing external levels could work OK. existing external levels could work OK.

■■ Con - the aspect is north facing. ■■ Con - the aspect is north facing.

■■ Con - seems noticeably dark due to orientation, and ■■ Con - seems noticeably dark due to orientation, and proximity a large existing trees. proximity a large existing trees.

■■ Con - ﬂoor to ceiling heights are low. ■■ Con - ﬂoor to ceiling heights are low.

■■ Caution - check overlooking distance to residential block to the north. (Although the overlooking distance will be the same for existing upper ﬂoor ﬂats)

Longford Walk - constraints and opportunities Crosby Walk - constraints and opportunities

Longford Walk & Crosby Walk- existing section ❚ 6.0 Typical Block Study 1- Residential

Plan Setting Out:

■■ Typical bay width of 10.5m (estimated) between the deeper down-stand beams

■■ Depth of unit limited by daylight requirements (TBC) and column grid

■■ Resulting Unit Area = 61m2 (approximate)

■■ Follows existing building line, entry via communal corridor

■■ Leftover deep space could be utilised for storage

Sectional Setting Out:

■■ Existing undercroft height from top of structural slab to underside of slab = 2.25m (estimated)

■■ Works to reduce slab levels sufﬁciently required to apartment and corridor zone

■■ A reduction of circa 0.5m would be necessary to provide a clear height of 2.4m (subject to structural constraints)

■■ NB This assumes a relaxation in comparison to LHDG requirements for 2.5m minimum

Other Design Considerations - Location of external retaining wall minimises impact on existing parking and landscaping Proposed Plan-Study1 - Single aspect design not ideal for north facing conditions

Proposed Section-Study1

Cressingham Gardens Residential Conversion Feasibility ©TIBBALDS FEBRUARY2016 12 ❚ 6.0 Typical Block Study 2- Residential

Plan Setting Out:

■■ Typical bay width of 10.5m (estimated) between the deeper down-stand beams allows for one apartment to be accommodated

■■ Resulting Unit Area = 66m2 (approximate)

■■ Projecting glazed bay enhances daylight and aspect assuming external entry

■■ Leftover deep space within undercroft sufﬁcient for single sided parking zone

Sectional Setting Out:

■■ Existing undercroft height from top of structural slab to underside of slab = 2.25m (estimated)

■■ Works to reduce slab levels sufﬁciently required to apartment zone

■■ A reduction of circa 0.5m would be necessary to provide a clear height of 2.4m

■■ NB This assumes a relaxation in comparison to LHDG requirements for 2.5m minimum

Other Design Considerations: - Projecting bay enhances daylight penetration and Proposed Plan-Study2 opportunities for dual aspect - Location of external retaining wall further away from building edge enhances daylight and creates opportunity for external entry

Proposed Section-Study2

©TIBBALDS MONTH 2016 Cressingham Gardens Residential Conversion Feasibility 13 ❚ 6.0 Typical Block Study 3- Non-residential

Plan Setting Out:

■■ Typical bay width of 10.5m (estimated) between the deeper down-stand beams

■■ Study proposes potential light-wells to increase usable depth

■■ Resulting Unit Area (full bay width) = 132m2 (approximate)

■■ Projecting glazed bay enhances daylight and aspect assuming external entry

■■ Leftover deep space within undercroft could be utilised for storage

Sectional Setting Out:

■■ Existing undercroft height from top of structural slab to underside of slab = 2.25m (estimated)

■■ Works to reduce slab levels sufﬁciently required to undercroft zone

■■ A reduction of circa 0.5m would be necessary to provide a clear height of 2.4m

■■ NB This low in comparison to commercial best practice

Other Design Considerations: - Projecting bay enhances daylight penetration and Proposed Plan-Study3 opportunities for dual aspect - Location of external retaining wall further away from building edge enhances daylight and creates opportunity for external entry

Proposed Section-Study3

Sitewide issues that would need to be considered at a strategic level:

■■ Parking strategy - if all the basement parking (and possibly the at-grade parking next to Hardel Walk), there will a big reduction in the amount of residential parking available. At the same time there would be an increase in the number of households.

■■ London Design Guide 4.9.1 requirement for 10% wheelchair housing. If this applies to the uplift in dwellings a wider review of access would be required to the blocks. The structural bay size may not lend itself.

■■ Generally the existing estate does not easily facilitate disabled access.

■■ Need for renewable energy on site? There would need to be a strategic response to this.

Hardel Walk - At-grade parking currently in use Some areas of the basment car parks appear to be well used

There are some other examples of garage to residential conversion schemes in London. It is not clear if all of them have been built yet. The following pages illustrate some of them. However it is worth noting that:

■■ Low ceiling heights are a noticeable feature of all of the schemes;

■■ Most (though not all) successful schemes have the beneﬁt of being dual aspect.

Vulcan Way, Islington

■■ 60 disused garages converted to residential use/

■■ Single aspect homes converted from undercroft garage space.

■■ Bay windows used to maximise daylight.

■■ Existing services retained within a storage zone at the rear of the dwelling.

■■ Exisitng concrete ﬂoor was removed and a new ﬂoor cast at a lower level.

■■ Min ﬂoor to ceiling height shown = 2.3m.

Vulcan Way, Islington

Section thorugh existing parking and the new apartments (diagram from planning application - drawing AP(0) 231. P2)

Clarence Gardens, Regents Park

Initial Feasibility Study work undertaken by Tibbalds Planning and Urban Design

■■ Proposal to convert a number of under-used garages at the base of existing residnetial blocks.

■■ A series of single aspect 1 and 2 bedroom ﬂats or studio workshop units in the basement garage areas.

■■ Privacy strips provided.

Clarence Gardens - proposed plan Clarence Gardens - proposed section

Parkhurst Road, Islington

■■ This scheme has planning permission.

■■ Dwellings designed to ﬁt within exisitng strcutural grid.

■■ Initially, single aspect dwellings were proposed but this severely reduced the number of units possible and resulted in a scheme that was not viable.

■■ Light brought in through a new lightwell from the walkway above without impeding access for existing dwellings at upper level.

■■ Light ﬁnished and materials used at lower levels to increase perception of brighness in the new homes.

■■ The existing garages beneﬁtted from generous ﬂoor to ceiling heights.

Parkhurst Road - proposed plan (diagram from planning application - Design and Access Statement)

Parkkhurst Road - proposed section (diagram from planning application - Design and Access Statement)

Although converting the existing basement car parks to If the option of converting the car parking to residential use residential use may at first seem to be cost-effective and were to pursued, we would recommend that the following practical solution. Some of the issues mentioned in this work be carried out in order to gain a greater understanding report could prove to be expensive to overcome, in order of costs: to deliver residential accommodation of sufficient quality to ■■ Detailed survey of the basements; satisfy the London Housing Design Guide. ■■ Capacity study to assess the number of dwellings that The following principal issues have been identified in might actually be achieved; relation to the residential conversion of the parking areas at Cressingham Gardens: ■■ Services review / investigation with recommendations on how to arrange services to fit around the proposed ■■ Insufficient floor to ceiling heights mean that new ground floor flats, whilst still servicing the existing residential accommodation would not be able to meet apartments above; the requirements of the London housing design guide (LHDG) without expensive and potentially significant ■■ Structural advice impact on foundations of lowering excavation works. internal floor levels.

■■ Concerns about sufficient daylighting into the units. In In addition the conversion of certain blocks could result order to help overcome this large areas of glazing would in significant disruption to existing residents. For instance be required which may compromise residents privacy in the external works scheme required next to Hardel Walk in these locations. order allow access, private amenity space and sufficient daylighting would result in major works around this block. ■■ Most of the units would be single aspect north facing homes which would not be in accordance with LHDG. As an alternative to provide more homes, whilst retaining the existing dwellings, it may be more viable to provide ■■ Large areas of space would be left over without any additional space by building over the single storey / two natural light and so may not be very usable space. This storey elements of the existing blocks, using lightweight could possibly be used for storage or car parking but construction techniques. Although this too could result in without the current overlooking would be even less considerable disruption to existing residents. secure than the current parking areas.

■■ The need to relocate services that sit within the parking areas or deal with these within the new homes (note other garage conversions have had problems due to water ingress).

■■ The private amenity space required by the LHDG would be hard to achieve in some locations and would need to be taken from adjacent public realm areas within the estate.

■■ Because of the bay widths and downstand beams the areas may be more suitable for conversion to smaller 1 bed homes rather than larger or family units

■■ In some locations the conversion would mean bedrooms located on the ground ﬂoor/semi-basement facing onto the busy Tulse Hill, which is not an idea arrangement.