Adaptive Reuse, Issue #1: How to Navigate Recent U.K. Legislation Changes

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Eddie Jump, BEng, CEng, FICE Director Eddie’s wide-ranging expertise includes working with clients to find value in complex urban sites in London. His diverse portfolio ranges from the delivery of six-storey extensions atop Grade II* listed buildings to schemes for low-embodied-carbon towers, all within the City of London.

+44 7799 765988 EJump@ThorntonTomasetti.com

Sabina de Jesus, MEng, CEng, MIStructE Senior Associate Sabina is an experienced structural engineer who has worked extensively on refurbishment projects in the commercial, education and leisure sectors, from concept through delivery.

Her portfolio includes commercial extensions such as Easton Street in Farringdon and the conversion of commercial buildings into leisure facilities, such as Minories in London.

+44 203 900 2923 SDeJesus@ThorntonTomasetti.com

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ADAPTIVE REUSE

Issue #1:

How to Navigate Recent U.K. Legislation Changes As we move to a zero carbon economy, the reuse of buildings will increase, and recent legislative changes to encourage building extension are amongst the government’s first steps towards a lower-embodied-carbon construction industry.

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A Collaborative Response to Climate Change

Climate Change, Growing Population & the Decline of High Street The events of 2020 motivated us to rethink our definition of city – what it means now and what it might mean in the future. Everything about how we work; go about our daily lives; and use our surroundings, infrastructure and built environment is changing.

This has accelerated trends that were already affecting society, with climate change, technology, a growing population and e-commerce shaping our lives to the detriment of the high street on a scale that was unimaginable just a few years ago.

Our Thinking Much of our current building stock performs inadequately to prevent global warming, and technological changes are causing major disruptions in sectors of the built environment, such as retail.

The COVID-19 pandemic has accelerated the decline of brick-andmortar retail and compelled office personnel to work remotely, prompting firms to plan enhancements to the functionality of their workplaces to attract employees back.

As some sectors struggle, building stock will be freed up to adapt to market needs, permitting low-value or vacant buildings to be repurposed based on value rather than on the previously narrow Use Class system.

Meanwhile, as we pursue our 2050 commitment to reduction of climate change, building standards will adapt at an unprecedented rate, affecting new and refurbished building stock as we adapt all buildings to support a far lower embodied-carbon future.

This document, the first in a series exploring how such trends will impact the built environment, focuses on engineering opportunities relating to recent planning changes.

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Retain & Reuse Should we demolish and rebuild or retain and reuse? This is a fundamental question at the outset of many projects. The move to zero carbon commitment in construction will increasingly impact this choice as planning authorities encourage the retention of buildings.

With this in mind, the U.K. government is prioritising extension over replacement by enacting a series of changes to planning legislation.

Two recent key changes relate to the repurposing of buildings on high street and in town centres: • Permitted Development • The new Use Class system

Permitted Development to Rebuild Where Buildings are Vacant 1 From 31st August 2020 The revised legislation includes a new Permitted Development right allowing the demolition and rebuilding of “vacant and redundant” office and light industrial buildings into dwellings, without planning permission. This right applies when a building has been vacant for more than six months. Buildings must measure less than 1,000 square meters on plan, but replacement buildings may be up to two storeys taller than existing ones, so long as they are less than 18 meters tall.

The existing building must be one that was constructed before 1990 and may not be located in a conservation area, national park or a site of special scientific interest.

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The Town a n d C o untr y P l an n i n g ( Us e C l a s s es ) ( A m en d m ent ) ( En g l a n d ) Regu l at io n s 20 20. https://ww w. l e g i s l ati o n . g ov. uk/uks i / 2 0 20/ 7 5 7/p d f s /u k s i_20 20 07 5 7 _en . p d f

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Climate change is among the factors that will determine how we use our built environment in the future.

Permitted Development to Increase Building Height 2 From 31st August 2020 New Permitted Development rights will enable the upward extension, by up to two storeys, of existing post-war homes. These rights will extend to the creation of new homes above terraces, offices and shops, without requiring planning permission outside of conservation zones.

The Creation of a New Use Class 3 From 1st September 2020 The creation of new Use Classes allows businesses to alter the use of a property without seeking planning permission for changes of use within the same Use Class. Existing buildings that are already used for Class A1, A2, A3 and B1, and certain D1 and D2 uses, will fall within a new single Class E.

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As high-street businesses struggle, changes to legislation will allow underused

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buildings to be repurposed based on value.

Use Classes are as follows:

Class E – commercial, business and service.

Includes a variety of uses that are now considered in the same Use Class, including: • Retail • Restaurant • Financial, professional or other commercial services • Publicly accessible indoor sport, recreation or fitness • Publicly available medical or health services • Crèches, day nurseries and day centres • Offices, including research and development • Industrial uses which do not harm amenity

Class F1 – learning and non-residential institutions.

Includes community-type uses for the general public. For example: • Schools • Libraries • Art galleries

Class F2 – local community facilities.

Includes community-type uses for physical group activities such as: • Community halls and meeting spaces • Swimming pools • Skating rinks • Areas for outdoor sports • Rural community local shops • Residential development local shops Buildings that do not fall into any particular Use Class are categorised as “sui generis.” The new regulations confirm that certain changes of use in this category are prohibited without planning permission.

Building types newly classified as “sui generis” include drinking establishments, hot food takeaway, live-music venues, cinemas, concert halls, bingo halls and dance halls.

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ADAPTA B I L I T Y G UID E BY B UI L D I N G TYPO LOG I ES I N T H E UN IT E D K IN GD O M RETAIL

Sector

COMMERCIAL

Current Use

Class A

Thornton Tomasetti Adaptability Index

Highly suitable for change.

Highly suitable for change.

Highly suitable for change.

*****

*****

*****

Historic buildings of hollow pot concrete slab/steel filler joist and steel encased in concrete and masonry walls.

Reinforced concrete frame.

Reinforced concrete frame.

Class A1/2/3 revoked from 1st September 2020, effectively replaced by the new Class E without planning permission 1, 2.

Class A1/2/3 revoked from 1st September 2020, effectively replaced by the new Class E without planning permission 1, 2.

Class B1 revoked from 1st September 2020, effectively replaced by the new Class E without planning permission 1, 2.

Most Common Type of Construction

Legislation Changes

1,2

Class A

1,2

Class B (B1)

1,2

New permitted development rights 1 (AA) allow extension of 2 storeys of residential use on top of an existing building of 2 storeys or more.

Suggested Change of Use

Extension Potential (storeys)

Residential and mixed-use Class E, including retail, collaborative workspaces, community hubs and leisure.

Residential and mixed-use Class E, including retail, collaborative workspaces, community hubs and leisure.

Residential extension and mixed-use Class E, including retail, collaborative workspace and community hubs.

Up to 100%

Up to 65%

Up to 100%

Di s c l ai me r:

T h i s tabl e is inten d ed to p rov id e in it ia l gu id a n ce a n d over v iew of t h e variou s as pect s o T h e f i n al des ig n req u ires en g in eer in g ver if ic at io n o n a c a s e- by- c a s e bas is , an d as s es s m T h i s i ntro du c to r y gu id e rel ates to p l a n n in g regim e fo r En g l a n d a n d is n ot a def in it ive s o

Refe re n ce :

1 . T h e Tow n a n d C o u nt r y P l a n n in g (G en era l Per m it ted Devel o p m ent ) (En g lan d) (Am en dm 2 . https : //www. p l a n n in g p o r t a l . co . u k / info / 20 01 30/co m m o n _p ro j ec t s /9/ch an g e_ of _ u s e

RESIDENTIAL

Class B (B1)

LIGHT INDUSTRIAL

Class C (C3/C4) 1,2

Class C (C3/C4)

Highly suitable for change.

Somewhat adaptable.

Somewhat adaptable.

Suitable for change.

*****

**

**

****

Reinforced concrete frame.

Concrete floors with load-bearing masonry walls.

Reinforced concrete frame.

Historic buildings of hollow pot concrete slab/steel filler joist and steel encased in concrete and masonry construction.

Class B1 revoked from 1st September 2020, effectively replaced by the new Class E without planning permission 1, 2.

Class C is not affected by the 1st September 2020 changes.

Class C is not affected by the 1st September 2020 changes.

New permitted development rights 1 permit the construction of up to 2 additional storeys of residential accommodation on top of existing, purposebuilt blocks of flats, where the existing dwelling house is 2 or more storeys tall, or one additional storey where the dwelling house consists of one storey.

New permitted development rights 1 permit the construction of up to 2 additional storeys of residential accommodation on top of existing, purposebuilt blocks of flats, where the existing dwelling house is two or more storeys tall.

B1(c) Business/industrial process revoked from 1st September 2020, effectively replaced by the new Class E.

Residential extension and mixed-use Class E, including retail, collaborative workspace and community hubs.

Additional residential and community hubs.

Additional residential and community hubs.

Collaborative workspace, leisure and community hubs.

Up to 65%

Limited to 4

Up to 20%

Up to 100%

1,2

New permitted development rights 1 (AA) allow extension of 2 storeys of residential use on top of an existing building of 2 storeys or more.

1,2

Class B (B1)

1,2

f a d a pt ive re use in the contex t of i m prove m e nt pote nti al . ment m ust be finalised based o n th e par ti c ul ar bui l d i n g ty p o l o gy, s ite co n d it io n s a n d s ite- s p ec if ic co n s t ra int s . ou rce of le ga l information.

ment ) (No . 2 ) Order 20 20 (S I 202 0/ 755) e

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67kg CO2/m2 SavedÂ

50% Height Added

Case Study The Record Hall Applying our knowledge and experience in façades, structural engineering and sustainability consulting, we contributed to the project’s decision-making process during the site-acquisition and opportunity-appraisal stages, even ahead of developing concept designs. This expertise enabled us to provide insight into the impacts of change of use and the building’s ability to accommodate extension and adaptation.

Dating from the late 1920s, the building housed office spaces and record storage for Prudential Insurance. In the late 1970s, Prudential sold the building to Camden London Borough Council, and it was later acquired by Workspace Group.

The Record Hall featured a single basement with four upper storeys that gradually stepped back from the site perimeter. Deep floor plates, narrow light wells and awkward circulation routes hindered our client’s ability to achieve a good rental return on investment.

In collaboration with Workspace and Karakusevic Carson Architects, we developed ideas for the building’s refurbishment and redevelopment. Through infilling and by adding roof extensions to double the height of the building, we increased its floor area by 40 percent, and by retaining the existing frame and much of the masonry façade, we saved 67kgCO2 per square meter versus a new-build option and 39 percent of the total embodied carbon.

We also saved an estimated year in construction time through refurbishment of the existing building.

The modern spaces are designed to promote well-being, with the new floors benefiting from natural ventilation and access to roof terraces while providing biodiverse green spaces. The existing floors’ greater access to daylight, thanks to the new light well, also serves to reduce operational energy consumption.

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