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City of Westminster – The Basements Revision to Westminster’s City Plan – Examination March 2016

Inspector’s Main Issue and Questions for the Council

1. The Council has addressed the duty to co-operate in Section 6 of its Consultation Statement. However, does it consider that the BR relates to a strategic matter as referred to in section 33A of the Planning and Compulsory Purchase Act 2004 in that it would have a significant impact on at least two planning areas?

1.1 While there is an argument that strictly speaking basements do not constitute a strategic matter, the council considers that as an issue of importance to a number of boroughs, and with similar issues, there is value in actively engaging, and for this reason the council has gone further in this regard than strictly necessary. The growing trend towards basement development is of importance to a number of Central London boroughs, including the Royal Borough of Kensington and Chelsea, and the London Boroughs of Camden and Islington, as well as other boroughs such as Richmond upon Thames. Trends in residential renovations, such as that of basement development will tend to ripple across other similar residential markets in neighbouring areas as homeowners facing space constraints in central London seek to increase the space in their homes. For those boroughs where space is at a premium, and where heritage designations limit the potential for rear or roof extensions a basement can offer a solution. However the extended construction period, associated noise, vibration and dust impacts as well as resulting impacts on highways and parking do negatively affect neighbours, and have cross-boundary impacts, both from increases in construction traffic, as well as noise and air pollution which does not stop at a borough boundary.

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2. What is the overriding purpose of the BR? Briefly, what is the justification for introducing a policy on basements development and what is it trying to achieve?

2.1 The overriding purpose of the BR is to provide a policy framework within which a balance can be struck between enabling basement development, and limiting the significant quality of life and other impacts arising for residents living alongside or near basement developments. This includes managing construction phase impacts relating to noise and traffic disruption, but also around longer term aspects such as ensuring structural stability of the building and neighbouring buildings and infrastructure, protection of heritage assets, protection of trees of townscape value, the provision of appropriate landscaping and protection of the character of the garden setting. There are also important ways in which the policy aims to provide a degree of cumulative protection on issues such as flood risk, from for example the loss of permeability and water storage capacity. The justification for introducing the policy relates to highly constrained densely populated nature of Westminster (with an average population per square km of 10,937 compared to 5,510 for London as a whole, or 468 for the South East1), with tightly knit streets which compound the negative amenity effects for those living nearby. With population and employment growth projected to increase there will be an increasing intensity of use in Westminster neighbourhoods, which will increase the sensitivity of amenity impacts. In this context imposing reasonable limits on the depth and extent of construction will:

(a) limit the amount of soil excavated, thereby reducing vehicle movements to and from the site, and the overall construction programme, and

1 Greater London Authority, (2015) London Datastore available at: http://data.london.gov.uk/dataset/land‐area‐

and‐population‐density‐ward‐and‐borough/resource/cc4e7e08‐3071‐488f‐bdd9‐a62cb1ed1c5c# 

 

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(b) limit the extent of excavation beneath a garden, thereby ensuring flexibility for potential future planting including for mature trees, which will maintain garden character; and reducing the likelihood of drainage problems and surface water flooding from loss of permeability and water storage capacity which could arise from the cumulative changes over time if gardens become increasingly built out.

3. How has the adopted Supplementary Planning Document (SPD) on Basement Development in Westminster operated in practice since 2014? Does it give confidence that the BR will positively promote sustainable development?

3.1 The adopted Basement Development SPD [B/EB/05] has operated well, providing applicants with guidance on information to be submitted with their planning application. Detailed guidance on issues such as the level of topsoil, a structural statement self-certified by a suitably qualified engineer and the submission of a Construction Management Plan have all been set out in the SPD, and have operated smoothly and effectively and without challenge, and presenting no operational problems, having been welcomed by applicants. However as an SPD this is only able to provide guidance and the adoption of the policy is required to formalise these arrangements by giving them development plan policy status

3.2 Guidance on the hierarchy of listed buildings, which is aimed at ensuring that alterations do not adversely affect the significance of listed buildings is also contained in the SPD. A recent appeal decision [B/EB/10] on the creation of a sub-basement beneath a listed building, found in favour of the Council, referencing the SPD.

3.3 This gives confidence that the policy requirements which formalise those elements are appropriate, deliverable, and accepted by the development industry, and supports a conclusion that the policy will effectively promote sustainable development.

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4. What is the rationale for applying the policy to buildings originally built for residential purposes as well as existing ones? Is it realistic to expect that such buildings can be readily identified given the passage of time?

4.1 The rationale for applying the policy approach to buildings originally built for residential is that the impacts which the policy seeks to mitigate through its limits and requirements would be the same as for a residential typology. Proposed changes are set out in Appendix A. The criteria in the redrafted policy at B and C apply for the same reasons that they applied to residential buildings; because the site would be likely to have a garden, issues of landscaping and biodiversity are relevant and the character and appearance of the area is the same as for a residential area.

4.2 Although the policy wording has been reworked in Appendix A, it is noted that this does not alter the way in which policy applies buildings originally built for residential purposes.

4.3 The building typology in Westminster includes a large number of terraced houses of the 18th and 19th centuries, as well as Edwardian townhouses and later mansion blocks built for residential use. In the vast majority of cases, it will be obvious from visual inspection of the architecture whether they were originally built for residential purposes. Where this is not obvious the council has a range of historical sources available, including historic maps of various dates and documents such as the Survey of London, and records within our archives, which should allow the historical use to be established. Any building post-1945 will have a planning history and therefore its original use can also be identified. Further information sources can be found including listed building information, Conservation Area Audits, the Survey of London, Pevsner, title deeds and other records held by the landowner, particularly the Great Estates.

5. What is the justification for the specific limitations in A1a) in relation to site coverage (either 50% or 4m). Why have these figures been selected as opposed to higher or lower ones? Is this provision sufficiently clear? Would a diagram assist?

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5.1 The council has proposed a 50% figure with regard to development beneath gardens because it believes this to be a reasonable figure which strikes a balance between enabling individuals to add additional accommodation, while limiting the extent of garden excavation, and ensuring a reasonable amount of undeveloped land, which will support flexibility in future garden planting, including mature trees. Because average garden lengths across different parts of Westminster vary significantly (See page 6 Supporting Information B/EB/01) the 50% figure is felt to be reasonable. Furthermore, no alternative figure has been proposed to the Council.

5.2 The policy allows for a simple measurement of the allowance of basement area that can extend beyond the original building. It is 50% of the entire site minus the original building defined as ‘garden land’. This is preferable to multiple calculations for separate garden areas for example. This enables flexibility where sites have a larger front or side garden (which may also be more accessible), rather than necessarily limiting basements to back gardens. It is important that there is 50% of the garden land wherever that may be on the site in relation to the house. A measure of area rather than length is also more straightforward where gardens are not a regular shape.

5.3 A requirement for an undeveloped margin, which is supported in the Sustainable Design and Construction SPG [B/EB/03, page 29], will ensure that no garden will be developed in its entirety, (which would alter the character of gardens, constrain future planting options and biodiversity benefit, and cumulatively, could exacerbate flood risk for example). The intention is for this to apply to smaller sites as well as larger. While the Council has some sympathy for the reduction in net useable space that this may result in for smaller sites (particularly terraces of limited width), nonetheless this is considered to contribute towards meeting the aim of what was policy B2 (now A3b) i.e. “not increase or otherwise exacerbate flood risk on the site or beyond”.

5.4 In certain areas of the city, small courtyard gardens prevail. A strict adherence to the 50% figure in these cases is considered unreasonable, and so the 4m figure for those sites with gardens of less than 8m in length, affords such sites a reasonable allowance to enable

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them to meet their accommodation needs, e.g. a site with a garden of only 5m will be allowed to excavate 4m in that direction, rather than 2.5m, or almost the whole site if only 4m, subject to the need to provide a margin. The provisions of the General Permitted Development Order also allow up to 4m as ‘permitted development’, and it makes sense for the policy to align with this figure.

5.5 It is agreed that diagrams would be helpful for this part of the policy. These will be published this year either as part of a householder guide to basement development or as a revised Basements SPD or both. Early working diagrams are included at Appendix C.

6. Is the definition of “garden land” clear in A1a), on page 6 and the Glossary? The definition of “original building” in the Glossary is the same as in Annex 2 of the NPPF but should this be referenced in the third paragraph on page 6?

6.1 The use of the term ‘garden land’ in A1a) is considered clearer than the original ‘site curtilage’ in the Regulation 19 publication draft, which attracted comments regarding its lack of clarity. The definition of garden land is on page 6 and in the glossary, but the slight difference in wording between the two may create confusion. Amended text is suggested at Appendix A, bringing the policy application in line with the Glossary.

6.2 The Council agrees that the definition of the term ‘original building’ in the glossary could usefully be added to the policy application to assist with interpretation of garden land, which refers to this term. The amendments to the policy application set out in Appendix A would address this.

7. What is the distinction between the TLRN and other public highways for the purposes of the policy in A1b)? What is the justification for the dimensions given in A11 and A12? Do the terms highway, footway and carriageway need to be defined?

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7.1 The change proposed in the Submission Draft at policy A1b) and a similar change at policy A11 results from a consultation response from Transport for London.

7.2 The council agrees that congestion and the impact on the highway’s functioning is an important consideration that equally applies to the City Council’s own highway network. Indeed, congestion on borough roads can contribute to congestion on TLRN ones and vice versa. Given that Westminster’s road network includes key roads such as Oxford Street, the impacts are potentially similar. Having considered this further the City Council considers that the Submission Draft wording at policies A1b and A11, which effectively treats the TLRN differently, would be better addressed by applying the requirements to all roads, rather than only the TLRN. Alternative wording is set out in Appendix A to apply the criteria raised by TfL to the whole Highway network (Appendix A, new subsection A3c). This addresses TfL’s concerns in part.

7.3 TfL consider that the ‘Publication Draft’ wording could be read as encouraging development beneath the highway. Appendix A includes amended wording to clarify that Submission Draft Policy subsection A1b, which applies an exception for one boundary is only applied where development under the highway is going to happen in any case. This applies in the relatively limited numbers of cases: 54 applications for residential pavement vault excavation have been received since 1st April 2011. It is considered that this wording addresses TfL’s concerns whilst being more positively prepared, and clearer than the Submission Draft wording, which had been proposed by TfL.

7.4 The dimensions in policy provisions A11 and A12 reflect current UDP policy TRANS 19 [BMU/SD/02], and are considered necessary to ensure that where such development is taking place, sufficient space is retained for the provision of essential services and street furniture as well as maintaining the integrity of the highway. This policy has been applied effectively in the past.

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7.5 Primary legislation does not define the term ‘Highway’, and as it is a complex field, there is a risk that a poor definition could create unintended loopholes. In practice, existing policies which refer to highway, carriageway and footway, have been applied without difficulty or challenge and for this reason a definition is not proposed.

8. What is the rationale for limiting development to only one storey in A3? Is the definition of “large site” sufficiently clear?

8.1 The rationale is to limit the disruption to neighbours. This will be achieved by a limit on the amount of soil that must be excavated, (indirectly reducing the length of the overall programme), as well as limiting vehicle movements to the site (i.e. fewer vehicles to remove excavated soil). While the relationship between programme and size of basement is not necessarily straightforward, it is linked to site access as well as construction methodology as set out at page 4 in a further Baxter Report being tabled as EX/08 (enclosed). While smaller basements require from around 65 lorry movements, the largest deeper basements can require up to 700 lorry movements. [See page 8, Supporting Information B/EB/01]. Therefore the proposed ‘exceptional circumstances’, for which the single storey limit may be relaxed, is limited to large sites with high levels of accessibility.

8.2 The term ‘large sites’ has purposely not been defined, as in

Westminster this is felt to be a relative measure, owing to the variable sizes of development sites across the borough. Changes made in the submission draft included additional wording in the policy application expanding on how, for the purposes of policy A3a, sites will demonstrate that they are a “large site with high levels of accessibility”. While this will depend on circumstances, it would generally include being able to accommodate plant and machinery onsite and appropriate access to the rear or side of the site for example.

9. What is the justification for requiring a suitable pumped device in A13 given that the Alan Baxter report recommends this for high risk areas?

9.1 This change was proposed by Thames Water on the basis that new basement development be protected against risks of sewer flooding,

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with additional supporting text also inserted into the reasoned justification explaining that the alternative of a ‘non-return valve’ is not effective in directing sewage away from the building. The Baxter Report [B/EB/02] makes clear at s 4.3.3 that this risk links to periods of high rainfall when surface water flooding overwhelms the main sewers, which cannot cope, leading to other sewers backing up. Although the report [B/EB/02] includes a map of critical drainage locations at Figure 7, this is indicative only for initial guidance purposes, and shows areas where there is a significant increased risk of drains being surcharged during heavy rainfall events. This includes the majority of Westminster. Areas outside this may be at lower risk, but there is still a risk, and for this reason the inclusion of this provision is endorsed.

10. Having regard to the findings of the Alan Baxter report and the SPD, should the policy contain a provision that expects proposals to demonstrate that increased flood risk would be avoided?

10.1 Policy provision B2 (now A3b) requires applicants to demonstrate that their development will “not increase or otherwise exacerbate flood risk on the site or beyond”.

11. The Consultation Statement indicates that guidance is to be provided on how the hierarchy of a listed building and its significance is to be assessed (Response 8 to comments on CM28.1). What is the current position?

11.1 Guidance on this point is included in the current Basements SPD [B/EB/05, page 28].

12. Are the occasions when basements for non-residential development or for new build residential development should be judged against the criteria in the policy sufficiently clear and precise in Part C? Is the reference to adjoining residential properties apt? In any event, should this also be reflected on the first line of Part A?

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12.1 On reflection the wording in part C could be improved. In addition, and following further consideration of the comments by the WPA, it is considered that greater clarity could be given to which criteria would be applied to which types of development. Changes have been proposed in Appendix A to address this. The changes will each be taken in turn below.

12.2 The revised Part C removes the following development types from the requirements to meet the following criteria set out in paragraphs 12.3-12.7 below:

non-residential development adjoining residential, and new build residential, within the core commercial areas where there is potential for similar impact, and

12.3 Limits on extent of garden land and margins, and requirements for soil depth: The provisions relating to garden land, an undeveloped margin, and soil depth should not apply to non-residential development in the Core Commercial areas because in most cases these sites would rarely have a garden on which to apply this provision. Those that do, would most likely be buildings originally built for residential purposes, and therefore the provision would apply under that criteria. Similarly the provisions relating to soil depth should not apply to commercial development in these locations because commercial buildings will usually occupy the whole site.

12.4 This criteria should not apply to new build residential in the Core Commercial Areas because within these areas net gains in residential floorspace tend to have commercial floorspace at the lower floors and be on very constrained sites, occupying most of the site area at ground floor level. There is therefore not the same need to limit the extent of construction, and a larger basement which enables parking and storage onsite may be appropriate. A new build residential building in this area may also be more likely to develop up to the site boundary.

12.5 Notwithstanding this, there will still be a requirement for them to mitigate any surface runoff under A3b).

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12.6 Limiting to a single storey of basement development: Part C excludes non-residential development in the Core Commercial Areas from this criteria. Because these areas are characterised by a vibrancy and level of construction activity that will generate a higher level of background noise, the impacts are not the same as in parts of the city characterised as more residential. In those areas identified, the economic benefits of the additional commercial floorspace would outweigh the short term harm caused by the development construction nuisance and would maximise the development opportunity of the site without demands for excessive height and bulk.

12.7 In new build residential schemes in Core Commercial areas, basements are usually proposed to accommodate car parking, storage for waste, cycles, and plant. The council supports reducing pressure on street, and for this reason believes that in these parts of the city for these types of development an exception to the limit on a single storey is indeed justified.

12.8 The revised Part B is the same as the submission draft policy in effect.

12.9 Revised Part A clarifies that the Submission Draft section B applies to all basements, not just those referred to in the Submission Draft section A. The exception to this is safeguarding significant archaeological deposits, which it is considered all basement development must do. For this reason it has been moved to part A.

12.10 Making these changes allows us to give greater certainty for applicants in line with the NPPF, and ensure that it is only applied where necessary to address impacts. It also addresses the point about the possible need to refer to non-residential and new build residential in part A. Consequential changes have also been made to the policy application policy application, with a map at Appendix B.

12.11 The term “adjoining” was used because most significant impacts are likely to be in terraces or semi-detached properties: a basement excavation in an adjoining building results in a range of impacts such as noise, dust, vibration, but importantly including structural stability. the residential properties is considered apt. It was for this reason that

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that term was used. However the council does accept that adjacent could also be appropriate. However this term can be imprecise and difficult to apply. Use of the term “adjoining boundary” could be a suitable alternative to both of these.

13. Some representors say that the policy should go further in relation to listed buildings, terraces, properties with existing basements, self-certification, controlling highway impacts and hours of working. These matters have been responded to in the Consultation Statement but does the Council wish to add anything to those comments?

Listed Buildings

13.1 With regard to listed buildings, from a structural engineering viewpoint, whether a building is listed generally makes little difference to the overall engineering challenge [Baxter’s Report B/EB/02, para. 5.1.6]. The Council does not therefore consider there is evidence to support a ban on basements under all listed buildings, but instead has developed an approach more in line with national guidance, which considers first and foremost the impact on the significance (National Planning Policy Framework, para. 129). The policy therefore identifies the elements of significance most likely to be affected by basement development. Taking into account Westminster’s building stock, the council considers that the aspects of significance basement development is most likely to affect, and which differentiate this from other forms of development, are the impacts on original vertical hierarchy of spaces and historic fabric.

13.2 With regards to hierarchy, this approach has been informed by the significant number of Georgian and Victorian terraced houses in Westminster. Guidance on London Terraced House 1680-1860 produced by English Heritage [EX/11] notes that, although London terraced houses are varied, certain aspects of their character are common to their special interest and it specifically points to the importance of hierarchy of spaces. Where basements are proposed under London terrace houses which have a characteristic hierarchy of spaces, this can be imbalanced by the addition of a basement storey.

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This has therefore been specifically identified in the policy and means that under many listed buildings in Westminster, basements will be unacceptable. Further guidance on this is set out in the Basements SPD and the council has been applying this approach and consistently supported in decisions at appeal in this [see for example, EX/09; EX/12; EX/13]. This approach is also supported by Historic England.

13.3 However, it should also be noted that there is a greater concentration of listed buildings across Westminster than in some other central London boroughs and these include large numbers of buildings from a wide range of eras. While there is a large percentage of Georgian and Victorian houses where the issue of hierarchy would apply, there are also a significant number of other building types, such as Victorian and later commercial (some originally residential) properties, mansion blocks and villas, or other building types converted to residential, where hierarchy is not regarded as something which strongly contributes to significance. In addition, the character of some of the larger Victorian/ Edwardian houses is that they have been subdivided and internally altered from early in their history and this again reduces the significance of hierarchy as an issue. With a range of types and ages of listed building stock, some will be more suitable than others, and solutions more easily engineered. In this circumstance, the specific reference to hierarchy of spaces in this policy is still considered the most appropriate, proportionate policy response.

13.4 In addition to the impact on hierarchy, in almost all listed buildings, the impact on the building fabric will be a key consideration and part of significance. If original, historic or other important fabric was to be removed as part of the basement construction, then a basement may not be acceptable. While the engineering challenges can usually be overcome as set out above, the degree of intervention required to construct a basement, means that there can be more significant impacts on fabric than with other forms of development. However, the importance of this will depend on the amount of historic or original fabric affected and its sensitivity.

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13.5 Other than the principles relating to hierarchy of space and protection of fabric, the policy requires applicants to demonstrate site-specific feasibility of approach. All listed buildings are subject to the requirement for a structural statement and supporting text seeks to ensure engineers working on listed buildings are Conservation Accreditation Registration for Engineers (CARE) accredited. Other detailed listed buildings policies and guidance also seek to protect listed buildings from any form of development which may harm their significance.

Terraces

13.6 In terraced properties, the key factor is likely to be whether or not the properties are founded on a stable sub-soil. If they are, then it should be feasible to install a basement without causing undue damage to adjacent buildings. However, if the terrace is subject to seasonal movements then a basement should be resisted. This is covered in the Baxter Report [B/EB/02] at Section 5.4. The Council considers that the flexibility of its wording of what was part B (now part A, Appendix A), around provision of a structural methodology statement, will enable those in terraces, to demonstrate that the basement is feasible, and where the structural stability cannot be demonstrated this will not meet the requirements of B1 and B4 and will therefore be refused.

Properties with existing basements

13.7 The policy is proposed to limit to one storey in addition to the lowest original floor – so that those properties with an original basement layer might excavate one additional level – being afforded the same approach as others, on the basis that one additional level would not generally result in more disturbance than one storey excavated in a building with no existing basement, subject of course to the applicant demonstrating the general feasibility requirements of part B of the policy. However the link with the ‘original’ building is intended to prevent repeated applications to excavate deeper and deeper.

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13.8 The Baxter Report [B/EB/02 at para 6.6] highlights potential risks to existing houses with basements or lower ground floor areas where the “existing perched water level is close to the lowest occupied area”. In these circumstances new basements construction in the vicinity could “slightly raise groundwater levels ‘upstream’”, which could cause some previously dry basements to become damp or wet. The report advocates very careful consideration in these circumstances, and advises an extended monitoring of groundwater pre- and post-construction, as well as incorporation of drainage measures to provide flow paths around or under the basement. The Council considers that its policy provisions at what was part B (now part A, Appendix A) adequately covers this, with the requirement for applicants to “take into account site-specific ground condition, drainage and water environment(s) in the area of the development”. This does not necessarily merit an outright ban on additional basement development.

Self Certification

13.9 With regard to self-certification the Council believes its approach of relying on the skills of suitably qualified professionals, the professional duty of care owed to the client, and the existing civil law remedies between neighbours is the only practicable way forward because it does not retain the skills in house to be able to sign off such statements.

Controlling highway impacts

13.10 The Council is currently consulting on its Code of Construction Practice [EX/10], with the end date for this consultation Monday 22nd February. The responses from this will be collated and summarised ahead of the basements examination.

13.11 In particular, in the draft Code of Construction Practice the Council has taken on board comments raised by Knightsbridge Association regarding the possibility of timing the granting of its highways licences in such a way as to ensure the free flow on its highway network (which includes both footway and carriageway). While the council is clear that

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this is a power of last resort, which would only be of use in limited circumstances, it has explicitly referred to its powers under s16 Traffic Management Act 2004 and s122 Road Traffic Regulation Act 1984 in the draft Code at section 1.10 and 5.2.

Hours of Working

13.12 The Council’s draft Code of Construction Practice [EX/10] contains provisions regarding limits on working hours, which have been amended with regard to residential areas, to take into account the strength of comments regarding construction site noise. Section 3.2 states that

“Core working hours will be from 0800 to 1800 on weekdays and 0800 to 1300 on Saturday. In residential areas noisy works associated with a development (e.g. demolition, piling and earthworks) will be limited to weekdays from 0800 to 1800 hours, unless otherwise agreed.”

Comments relating to the Basements Revision indicated that while basement construction noise was of particular nuisance, all types of construction noise at weekends were unwelcome. Therefore the Code of Construction Practice imposes limits on all noisy works associated with all types of development covered by the Code in residential areas, rather than just associated with basement development. This aims to allow a certain flexibility with regard to works that are not noisy, but will avoid a situation whereby basements have restrictions, but other sites do not, which might render a limit on basement construction pointless, where neighbouring building sites are able to proceed on Saturday mornings.

13.13 Although some representors have suggested that an 08:00am start is too early, this is considered to be an industry standard, which also takes account of daylight hours, employment, school start times and general traffic and noise build up. Later starting hours every day would also be likely to result in a longer programme.

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14. Does the BR have clear and adequate mechanisms for monitoring the effectiveness of Policy CM28.1?

14.1 The council proposed two monitoring objectives, relating to numbers of Sustainable Urban Drainage Systems, and number of Code of Construction Practice compliant schemes. These are intended to add to existing monitoring the Council undertakes relating to numbers of basement developments. Section 6 of the Integrated Impact Assessment B/SD/2E sets out the monitoring indices that will be collected and included in our Authorities Monitoring Report. Monitoring of these is considered to be straightforward, with the Code of Construction Practice monitoring visits affording an opportunity to monitor SUDs where these are to be provided.

14.2 However, additional or slightly amended monitoring objectives would aid the Council’s understanding of the effectiveness of elements of the policy. The following suggestions are considered clear indicators which can be monitored to demonstrate effectiveness of policy elements.

enforcement investigation relating to basements constructed not in accordance with the approved permission.

numbers of appeals for basements where the refusal relates to non- compliance with the basements policy.

numbers of appeals upheld on the grounds of impact on heritage assets or impact on the hierarchy of spaces; and enforcement investigation relating to the damage of listed buildings during construction of a basement.

numbers of basement permissions which include the loss or damage to a tree of townscape of amenity value; and enforcement investigations relating to damage to trees during construction of a basement.

proportion of applications permitted which do not include an adequate volume and minimum soil depth (of 1m plus drainage layer).

numbers of basement construction complaints received by Environmental Health.

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numbers of enforcement investigations relating to the discharge of pre-commencement conditions.

numbers of basements in imminent danger of collapse under the London Building Act. This will pick up dangerous basement structures which collapse, or are in danger of collapsing. It triggers powers that the council has to act in basements which the Council’s Building Control is not dealing with (i.e. are being dealt with by an Approved Inspector)

15. What is the position with the Article 4 Direction that is referred to?

15.1 The Council consulted on a non-immediate Article 4 Direction, to withdraw permitted development rights in respect of basement excavation or extension beneath a dwellinghouse or its curtilage. This is intended to apply across the whole of the city of Westminster. The use of the non-immediate rather than an ‘immediate’ Article 4 Direction is intentional, to avoid compensation being payable.

15.2 The Council received one objection from Cranbrook Basements regarding this Article 4 Direction. Two points were made in this objection. The first noted that Cranbrook Basements considered the use of the Article 4 Direction an unnecessary infringement of the house owner’s right, and that its use was not justified because the local amenity and wellbeing of the entire borough was not compromised. This referred to paragraph 200 of the NPPF, which requires Article 4 Directions to be “limited to situations where this is necessary to protect local amenity or the wellbeing of the area”. In response to this objection the council notes that basements do negatively impact amenity to such a degree, for such a length of time, and are distributed across all parts of the borough, being a densely populated area, such that a borough-wide article 4 is justified. [B/EB/01, B/EB/02].

15.3 The second point made was that a suggestion that because the applicant does not need to pay a planning application fee where its right to develop a basement is being removed, that the council should pay all costs associated with producing a planning application;

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“this means the full cost of assessing applications must be carried by the Council. The full cost should include the cost of producing all of the documents that form the planning application…. including Construction Method Statement, Subterranean Structural Method Statement and Construction Management”.

Effectively, Cranbrook Basements considers that compensation is payable in respect of this Article 4 Direction. This is not the case as the Basements Article 4 Direction:

applies to ‘prescribed rights’ under section 2 of the Town and Country Planning (Compensation) (England) Regulations 2015;

has been withdrawn in the prescribed manner (i.e. by way of an Article 4 Direction - section 3 of the Town and Country Planning (Compensation) (England) Regulations 2015); and

with notice of the withdrawal having been published in the prescribed manner not less than 12 months or more than the prescribed period (two years) before the notice took effect - section 3 of the Town and Country Planning (Compensation) (England) Regulations 2015 – in effect a minimum of 12 months’ notice of the withdrawal of the PD rights must be given.

15.4 The Article 4 cannot legally come into effect until it is confirmed. The period within which the Secretary of State could have amended or quashed the Direction has expired. Therefore consent for the Article 4 direction is deemed, and the Council will move to confirm it ahead of the summer.

Other Matters

In response to the other points raised the council thanks the Inspector for pointing out inconsistency with regard to numbering and the need for the acronym CARE to be written in full.

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The Inspector rightly points out that the council has not made a change requested by one of those commenting on the draft policy. This is because prior to submission of the Regulation 19 draft it was agreed by Grosvenor in an email dated 12 November 2015 that as the Basements SPD [B/EB/05] already includes this wording that they were satisfied, and the change need not be made in the policy supporting text.

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APPENDIXA:SUGGESTEDCHANGESBlue ‐ changes between adopted text and Pre‐Submission Regulation 19 version Red ‐ changes between Pre‐Submission Regulation 19 and Submission Regulation 22 versions Green ‐ changes post‐Submission Regulation 22 version 

 

POLICY CM28.1 BASEMENT DEVELOPMENT 

A.  applicants All applications for basement development will:2  

1.  demonstrate that they have taken into account the site‐specific ground 

conditions, drainage and water environment(s) in the area of the development; 

2.  All applications will be accompanied by: 

a)  A detailed structural methodology statement and appropriate self‐

certification by a suitably qualified engineer with separate flood risk 

assessment where required. In cases where the council considers there is a 

high potential risk that the development will have significant impacts on the 

matters covered by this policy or where work will affect a particularly 

significant and/or sensitive heritage asset, the council will have reports 

independently assessed at the applicant’s expense.  

b)  A construction management plan will be provided to which demonstrates 

that the applicant will comply with adherence to the relevant parts of the 

council’s Code of Construction Practice and awareness of the need to comply 

with other public and private law requirements governing development of 

this kind. 

 

2 This was formerly in section B. See Question 12.  

22

 

  3.  All basement development will:3 

a)   safeguard the structural stability of the existing building, nearby buildings and 

other infrastructure including the highway and railway lines/tunnels; 

b)   not increase or otherwise exacerbate flood risk on the site or beyond;   

c)   be designed and constructed so as to minimise the impact  at construction design 

and occupation stages on neighbouring uses; the amenity of those living or 

working in the area; and on users of the highway; and traffic and highways 

function4; and 

d)  safeguard significant archaeological deposits. 

 

B.  Basement development to:5 

a)  existing residential buildings or buildings originally built for residential purposes; 

b)  non‐residential development adjoining residential properties where there is 

potential for similar impact on those adjoining properties; and 

c)  new build residential incorporating basements where there is potential for similar 

impact on those adjoining properties; 

will:  

1.  provide a satisfactory landscaping scheme, incorporating soft landscaping, 

planting and permeable surfacing as appropriate;  

2.  not result in the loss of trees of townscape, ecological or amenity value and, 

where trees are affected, provide an arboricultural report setting out in particular 

the steps to be taken to protect existing trees; 

3 This was formerly in section B.  4 See Question 7. 5 This section was formerly covered in section A but two additional development types have been added, derived from the previous section C.  

23

3.  use the most energy efficient means of ventilation, and lighting,  involving the 

lowest carbon emissions. Wherever practicable natural ventilation and lighting 

should be used where habitable accommodation is being provided;   

4.  incorporate sustainable urban drainage measures to reduce peak rate of run‐off 

or any other mitigation measures recommended in the structural statement or 

flood risk assessment; 

5.  protect the character and appearance of the existing building, garden setting or 

the surrounding area, ensuring lightwells, plant, vents, skylights and means of 

escape are sensitively designed and discreetly located; and 

6.  protect heritage assets, safeguarding significant archaeological deposits and in the 

case of listed buildings, not unbalance the buildings’ original hierarchy of spaces, 

where this contributes to significance; 

7.  be protected from sewer flooding through the installation of a suitable pumped 

device.  

will also be subject to the criteria set out above 

C.   Basement development to:6 

a)  existing residential buildings or buildings originally built for residential purposes;  

b)  non‐residential development adjoining residential properties where there is 

potential for similar impact on those adjoining properties outside Core CAZ, the 

Opportunity Areas and the Named Streets7; and 

c)  new build residential incorporating basements where there is potential for similar 

impact on those adjoining properties outside Core CAZ, the Opportunity Areas and 

the Named Streets;  

will: 

1.  a)   not extend beneath more than 50% of the garden land. site curtilage On 

small sites, where the longest distance between the existing building and any site 

6 This section was formerly covered in section A but two additional development types have been added, derived from the previous section C, and with additional area based criteria as set out in paragraph 12.1‐12.3. 7 See response to question 12, in particular paragraph 12.1‐ 12.3 

24

boundary is less than 8m, an exception will be made to allow the basement to 

extend up to 4m from the building in that direction. On all other sides of the 

building, the basement will not extend beneath more than 50% of the remaining 

garden land; and site curtilage 

b)   leave a margin of undeveloped garden land proportionate to the scale of 

development around the entire site boundary. Where D below applies, the 

boundary with the highway is excluded from this requirement. 8 

  with the exception of one elevation adjacent to the public highway9 (other than 

where the highway forms part of the Transport for London Road Network [TLRN])  10 where the basement may extend beneath the public highway provided it 

satisfies the requirements set out in paragraph 10 below.  

2.   provide a minimum of 1m soil depth (plus minimum 200mm drainage layer) and 

adequate overall soil volume above the top cover of the basement; 

3.   not involve the excavation of more than one storey below the lowest original 

floor level, unless the following exceptional circumstances have been 

demonstrated; 

a)  that the proposal relates to a large site with high levels of accessibility such 

that it can be constructed and used without adverse impact on neighbouring uses 

or the amenity of neighbouring occupiers; and 

b)  that no heritage assets will be adversely affected. 

 

D.   where constructing new Basement development under the adjacent (nonTLRN)11 

highway will: 

1.  retain a minimum vertical depth below the footway or carriageway of 900mm; 

and 

2.  not encroach more than 1.8m under any part of the adjacent highway; and 

8 See paragraph 7.1 9 See response to question 7, in particular paragraph  7.1 10 This change previously proposed by TfL is not supported by the Council. See response to question 7.  11 The Council does not support this amendment. See response to question 7, specifically paragraph 7.2 

25

3.  where extending or strengthening/improvement works to existing basements 

horizontally under the highway; 

a)  maintain the existing depth below the footway or carriageway to ensure no 

loss of existing cover level above a vault; and 

b)  will not be permitted where the existing basement already extends 1.8m or 

more under the highway.  

Policy Application 

This policy will primarily apply to basement extensions to existing residential properties but 

may also apply to new build residential incorporating basements, especially where these are 

located on constrained sites. 

This policy will apply differently for different types of application, with some provisions 

applying to all basements, and some applying depending on the type of basement. In terms 

of limits on the depth and extent of basement excavation, for new build residential and 

commercial basements, these apply to developments adjoining residential and where there is 

potential for impact on those properties, where the development is outside the Core CAZ, 

Opportunity Areas and Named Streets.12 

Garden land for the purpose of policy A1a) is the site area excluding the footprint of the 

original building.13 

The original building is, in relation to a building existing on 1st July 1948, as existing on that 

date, and, in relation to a building built on or after 1st July 1948, as so built14 

MONITORING FIGURE 56 MONITORING FRAMEWORK 

HEADLINEOBJECTIVES KEYINDICATORS’TOPICS POLICYREF   Objective2:Tosensitivelyupgrade Design quality (qualitative assessment)  25,26,28,

12 See response to question 12 13 See response to question 6 14 See response to question 6 

26

Westminster’sbuildingstocktosecuresustainableandinclusiveexemplarydesignwhichminimisesenergyandresourceconsumptionandtheproductionofwaste,reducestheimpactsoflocalenvironmentalpollutionandmeetsbothtoday’sneedsandthoseofthefuture,includingtheeffectsofachangingclimate;creatingattractiveplacesthatfunctionwellwhilstensuringthatthehistoriccharacterandintegrityofWestminster’sbuiltfabricandplacesisenhanced.

Sustainable and inclusive design measures as part of applications and, including where relevant, Code for Sustainable Homes level 

Protection and creation of heating networks  

Creation of new heat and cooling networks 

Extension of existing heat and cooling network 

Achievement of 20% renewable energy generation 

New waste and recycling facilities 

Number of developments permitted against Environment Agency advice on flood risk grounds,  Installation of SUDS measures, Numbers of appeals upheld on the grounds of impact on heritage assets or impact on the hierarchy of spaces; Investigation  and enforcement relating to the damage of listed buildings during construction of a basement, 

Numbers of appeals for basements where the refusal relates to non‐compliance with the basements policy,  Enforcement investigation relating to basements constructed not in accordance with the approved permission,  Numbers of basement permissions which include the loss or damage to a tree of townscape of amenity value; and enforcement investigations relating to damage to trees during construction of a basement;  Proportion of applications permitted which do not include an adequate volume and minimum soil depth (of 1m plus drainage layer).15 

 

 

28.129,30,31,32,33,35,36,37,38,39,40,41,44,45

Objective3:Tomaintainandenhancethequalityoflife,healthandwell‐beingofWestminster’sresidentialcommunities;EnsuringthatWestminster’sresidentscanbenefitfromgrowthandchange,providingmoreemploymentandhousingopportunities,safetyandsecurity,andbetterpublictransportandlocalservices;toworkwithourpartnerstofostereconomicvitalityanddiversity,improvedlearningandskills,andimprovedlifechancesin

Business space development by area (Economic Development Area, Central Activities Zone and Opportunity Areas) 

Number of vacant units in District Shopping Centres in the Economic Development Area (Church Street/Edgware Road and Harrow Road) 

Social and community infrastructure improvements and development 

New entertainment uses in the Economic Development Area, No of Code of Construction Practice compliant schemes, 

1,3,4,5,6,8,9,10,12,13,14,19,28,28.129,30,31,32,33,34,35,36,37,38,41,42,43,44,45

15 See paragraph 14.2 

27

areasofdeprivation. Numbers of basement construction complaints received by Environmental Health, 

Numbers of enforcement investigations relating to the discharge of pre‐commencement conditions, 

Numbers of basements in imminent danger of collapse under the London Building Act.16    

16 See paragraph 14.2 

28

APPENDIXB:MAP

29

APPENDIXC:WorkingDiagrams

A B

8m 10m

17m

10m

5m

32m

2m

To calculate the maximum in addition to the basement area 

beneath the original dwelling housing:

A

Basement   = 50% of site area minus original dwelling house)

  = 50% of (32m x 8m) – (17m x 8m)

  = 50% of 120sqm

  =  60sqm 

B

Basement   = 50% of site area minus original dwelling house)

  = 50% of (32m x 10m) – (17m x 8m)

  = 50% of 136sqm

  = 92sqm

It is up to the applicant where this is located on the site, subject 

to the undeveloped margin.

30

To calculate the maximum in addition to the basement area beneath the original 

dwelling housing for a small with less than 8m rear garden:

C

Basement   = rear garden allowance plus remaining allowance

Rear garden allowance (RGA) = 4m from rear of house at longest measurement

Remaining allowance = 50% of site area minus original dwelling house)

  = 50% of (15m x 5m) – (13m x 5m)

  = 50% of 10sqm

  =  5sqm 

D

Basement   = rear garden allowance plus remaining allowance

Rear garden allowance (RGA) = 4m from rear of house at longest measurement

Remaining allowance = 50% of site area minus original dwelling house)

  = 50% of (15m x 7m) – (13m x 5m)

  = 50% of 40sqm

  =  20sqm 

It is up to the applicant where the remaining allowance is located on the site, subject 

to the undeveloped margin.

Small Sites

C D

5m 7m

13m

5m

20m

2m

RGA RGA 4m

31

To calculate the maximum in addition to the basement area beneath the original 

dwelling housing for a small with less than 8m rear garden:

E

Basement   = rear garden allowance plus remaining allowance

Rear garden allowance (RGA) = 4m from rear of house at longest measurement

Remaining allowance = 50% of site area minus original dwelling house)

  = 50% of (15m x 5m + 2m x 2m) – (13m x 5m + 2m x 2m)

  = 50% of 10sqm

  =  5sqm 

F

Basement   = rear garden allowance plus remaining allowance

Rear garden allowance (RGA) = 4m from rear of house at longest measurement

Remaining allowance = 50% of site area minus original dwelling house)

  = 50% of (15m x 7m + 2m x 2m) – (13m x 5m + 2m x 2m)

  = 50% of 40sqm

  =  20sqm 

It is up to the applicant where the remaining allowance is located on the site, subject 

to the undeveloped margin.

Small Site with irregular rear wall

E F

5m 7m

13m

5m

20m

2m

RGA RGA 4m

2m

2m 2m