Character contradiction: The exclusionary nature of preservationist planning restrictions

Preservationist planning broadly describes planning instruments that purport to preserve physical qualities of neighbourhoods by preventing demolition of historic dwellings. Here, we analyse land use conversion of almost 6000 lots in Brisbane, Australia, to understand if, and how, preservationist planning impacts the built environment. Results demonstrate that preservationist planning suppresses multi-family housing construction, even where increased density is encouraged by the planning scheme. We suggest that preservationist planning is exclusionary in nature and not solely focused on built heritage, particularly as substantial modifications to existing dwellings are allowed. These findings run counter to the purported aim of built heritage protection and suggest that the preservationist planning framework should be revised.


Introduction
The debate regarding how best to preserve the heritage of the built environment vis-a`-vis the housing needs of an urban population remains central to many urban planning conversations (Glaeser, 2010).In most cases, an underlying tension exists between the priority of redevelopment, particularly at higher densities, and the rationale underpinning the conservation of historical building typologies.While the most ubiquitous tool for preservation is the designating of historic buildings, sites or neighbourhoods, a variety of planning tools also serve preservation aims (Avrami, 2016;Redaelli, 2021).Conservation overlays or zonings are widespread in the United States, Australia and New Zealand, and purport to '. . .protect ''neighbourhood character''' (Lemar, 2015(Lemar, : 1525)).This unique form of heritage protection, employed by planning authorities, differs from heritage listing by accommodating alteration to existing buildings, often subject to development approval by a local authority.
Preservation of older buildings tends to prevent redevelopment of existing lowdensity structures and ensures that new construction is of a similar scale (Avrami, 2016).This creates conflict between preserving historical low-density residential areas and allowing their redevelopment at higher density.Neighbourhoods targeted for increases to residential density are often in proximity to the central city, public transport infrastructure and high amenity areas such as waterfronts.These are often established neighbourhoods with older housing stock, making them targets for both high density and built heritage protections (Avrami, 2016).While architecture is prominent in decisions for or against built heritage protection, consideration of planning, socioeconomic factors, and the impact to property rights, are also highly influential in the decision-making process (Mualam and Alterman, 2020).
Many cities around the world currently face a 'housing crisis' (cf.Pawson, 2022 for Australia; Badger and Washington, 2022 for the United States) due at least in part to a failure to construct enough housing to keep pace with population growth and household formation.Cities with growth management or urban consolidation polices are often required to source most new dwellings from existing urban areas (e.g.greyfield and brownfield sites), known as infill development.These policies are implemented with intentions to prevent habitat destruction and loss of urban fabric tied to 'greenfield' development on the urban fringe.While historic preservation is extensively discussed in the planning and property economics literature, due to its ability to influence property prices, there is limited analysis on the built form implications of conservation overlays or zoning (Been et al., 2016;Glaeser, 2010;Tan and Ti, 2020).Most research focuses on the ability of conservation policies to prevent redevelopment (cf.Kovacs et al., 2008 in Canada;Tan and Ti, 2020 in Singapore; Neilsen and Pojani, 2020 in Australia).There is little analysis of the compatibility of historic preservation and densification goals, and whether preservation zoning regimes can respond to changing urban dynamics and housing preferences.
The conflict between densification of existing urban areas and the preservation of historic housing typologies is further compounded by the exclusionary nature of zoning more generally (cf.Grey, 2022), which preserves low-density residential areas (Longstreth, 2011), at times without a 'character' or 'heritage' designation in place.The term exclusionary zoning features largely in American literature (Taylor, 2013) and refers to any form of land use zoning that prevents low to middle income households from finding housing in a neighbourhood (Whittemore, 2021).While land use zoning cannot explicitly dictate who can live in a certain area, it can be an effective means of social segregation by increasing the cost of building or maintaining housing.There is a large body of literature on the intersection between historic preservation and gentrification (Allison, 2005;Bures, 2001;Jones and Varley, 1999).For example, while historic preservation in New York City contributed to the economic revitalisation of designated neighbourhoods, it did displace lower income residents (McCabe and Ellen, 2016).There is, however, a significant research gap in understanding whether preservation policies can simultaneously facilitate infill development.
This research aims to understand whether the practical outcome of preservationist planning results in built heritage preservation, and whether redevelopment can both conserve historic housing and increase residential density.We make a unique contribution to the literature by analysing land use transitions of almost 6000 houses from 1951 to 2021.We question whether preservationist planning is necessary to preserve built heritage.To answer this question, we focus on the city of Brisbane, a state capital city at the centre of one of Australia's fastest growing metropolitan areas.In addition to a legacy of low-rise housing and extensive preservationist planning that prevents the removal of historic houses (but allows modifications), Brisbane has significant pressure on housing supply, and state-sanctioned growth management policies that require almost all new dwellings to be sourced through infill development.This provides a unique opportunity to analyse how both preservation and infill policies influence redevelopment patterns.

Background
Built heritage is defined as any building or group of buildings that 'offer significant values and benefits such as the conservation of the history and narration of a city's existence' (Aigwi et al., 2021: 45).The protection of built heritage is a social process where buildings, monuments, structures, and areas are deemed to be of heritage value (Negussie, 2007).While some argue that conservation of built heritage effectively places public interest above private interest by seeking to protect the built environment for the common good (Phelps et al., 2002) and that heritage protection is an important tool to 'slow the pace of change' (Ashworth, 1997: 99), others claim that conservation policies artificially inflate dwelling costs, and prevent the construction of affordable housing, to the benefit of owners (Been et al., 2016).Defining what constitutes built heritage involves a complex group of stakeholders who compete to determine the future of a city (Short, 2007).Advocates for conservation argue that market-driven development is unable to protect built heritage, whereas critics argue that those advocating for conservation policies are another lobby group opposing change (Been et al., 2016).
Built heritage is generally protected through regulatory mechanisms, either legislative or policy, which seek to prevent inappropriate development or demolition (Short, 2007).Built heritage can broadly be conserved in two ways, through heritage listing, and through conservation or preservation strategies employed by planning authorities (Negussie, 2007).While both can be defined by legislation, and arguably contribute to local culture by linking current residents with the past (Tan and Ti, 2020), conservation strategies related to heritage listings of individual monuments or buildings do not generally support alterations to the original building (Tweed and Sutherland, 2007).In contrast, conservation strategies employed by planning authorities 'often epitomise a unique population density, historic nature, street pattern or other urban morphological or cultural feature' (Tweed and Sutherland, 2007: 63).These conservation strategies are described with varying terminology, ranging from historic, preservation or conservation districts or zoning, design overlay, demolition control precincts and many more (Avrami, 2016).For the purpose of this article, we describe any land use planning instrument that seeks to preserve a historic built form as 'preservationist planning'.Preservationist planning can stipulate allowable building uses, heights and profiles, and requirements for the building fac xade, roof, colour, and interior finishes (Kovacs et al., 2008;Tan and Ti, 2020).In most contexts, properties are graded on a point-scale, with the highest value being assigned to those of significant cultural value that cannot be altered without detailed plans, while the lowest value requires only the preservation of fac xades and other cosmetic elements.
Using zoning to influence new housing typology.Zoning has also long regulated the bulk and scale of buildings through maximum heights, setback requirements, lot coverage and floor to area ratios (Lemar, 2015).However, the suburban development that characterised the post-war period saw cities following a general trend of reducing flexibility in housing construction, with secondary dwellings ('granny flats'), duplexes and corner stores gradually prohibited in suburban estates (Grey, 2022).Preservationist planning instruments go beyond regulating land use and size by dictating aesthetic standards such as building materials, siting, and roof lines (Lemar, 2015).In jurisdictions with growth management, infill development is the primary source of new dwelling construction, often by local governments upzoning specific properties to allow developers to construct more dwellings on the same site than was previously allowed.It is viewed as a policy tool to increase housing supply and decrease dwelling prices (Rodrı´guez-Pose and Storper, 2020).Upzoning is, however, contentious as it has the potential to alter existing housing typologies in a neighbourhood.To this end, proposals to increase residential density are often met with community resistance, despite urban planning trends from the 1980s attempting to re-think carorientated design in favour of mixed land uses, transit-oriented development and higher density living (Raynor et al., 2017).As a result, while upzoning is used in some neighbourhoods to allow change to existing housing stock, low-density zones, including those aimed at built heritage conservation, are also used to prevent change or exclude housing typologies such as apartments.
Contemporary zoning cannot be uncoupled from its discriminatory history (Raitt, 2022), with social segregation being a major motivator for their introduction and subsistence (Whittemore, 2021).It has long been argued that land use regulations are a mechanism of preserving affluent areas, as 'minimum lot sizes and setback requirements ensure that only members of acceptable social classes could settle' (Jackson, 1985: 242).Exclusionary zoning tools are not the same in every jurisdiction (Whittemore, 2021) and examples include planning regulations that restrict the construction of multifamily dwellings such as apartments and townhouses by preventing their development altogether or imposing requirements around minimum lot sizes, car parking, setbacks and street frontages that make such developments unfeasible (Ihlanfeldt, 2004).By preventing the emergence of different housing typologies, low density residential zonings exclude residents that cannot afford the price of a house in the suburb.These regulations reduce the presence of rental properties (Pendall, 2000), with higher income neighbourhoods most likely to adopt restrictive land use zoning (Ihlanfeldt, 2004).
There is a large body of research that demonstrates how low-density residential zones have been used to ensure racial and economic homogeneity by restricting dwelling supply and elevating housing costs (Grey, 2022).Preservation of low-density residential areas through restrictive zoning practices bars many people from living in high opportunity and high amenity locations and ensures that opportunity is not evenly distributed across a metropolitan area, disproportionately impacting minority and low-income families (Manville et al., 2020).Research from Los Angeles shows that properties that were rezoned for higher density development were generally in areas with less political resistance (or influence) and areas with high political resistance were more likely to retain a low-density residential zone (Gabbe, 2017).Similarly, wealthier areas in Melbourne have higher levels of planning disputes and a greater number of objections to new development (Taylor, 2013).The conflict between densification goals and the preservation of historic housing typology makes planning decisions highly political.There is little investigation in the literature of the exclusionary nature of planning schemes with the purported aim of preserving historic housing typology (cf.Lemar, 2015;Taylor, 2013).
Preserving urban character in an Australian context.How neighbourhood character is defined and conserved varies depending on the jurisdiction.In Australia, character homes are generally those constructed prior to World War Two when the national population was less than one-third of what it is today.Often located within 5-10 kilometres of the centre of Australia's major cities, the former streetcar and railway suburbs were previously targeted for urban renewal, and pre-war housing considered slum-like and demolished.However, in the 1980s and 1990s these areas became highly sought after and property prices rose exponentially (Badcock, 2001;Pegler et al., 2020).
Queensland has a hybrid planning system where development compliant with the requirements of the relevant planning scheme must be approved.Discretion is also given to decision-makers to approve development that is not compliant with the relevant planning scheme zone code, but these applications must be publicly advertised, with properly made submissions providing the ability for community members to appeal the granting of a development approval, and decision-makers can consider any 'relevant matter' when assessing the application (Planning Act 2016 [Qld] 2021).The styles of character homes vary but they are generally detached single-family houses, colloquially referred to as 'tin and timber' or 'Queenslanders' (Neilsen and Pojani, 2020).
Brisbane homeowners use zoning to prevent densification of their neighbourhoods (Nielson and Pojani, 2020).A study of residents living in character houses in Brisbane shows conservation planning can be understood as protecting the local identity of a neighbourhood, but also as a 'manifestation of political and economic power' (Neilsen andPojani, 2020: 1058).In addition to purchase price, the maintenance cost of character houses can be large, with some residents associating maintenance costs with economic status and extensive renovation signifying greater financial power (Nielson and Pojani, 2020).There are some differences in how planning systems work in practice, and the discretion given to decision makers, but this study is applicable to any city that employs preservation through its planning framework.

Study area, data and methods
Brisbane is a sprawling metropolis at the centre of Southeast Queensland, one of the fastest growing regions in Australia, with a population of over 3.6 million in 2021 (Australian Bureau of Statistics [ABS], 2022).Like many Anglo-American cities, urban growth in Brisbane has been characterised by low density and car-centric peripheral expansion.In the 1970s and 1980s Brisbane became known as the 'demolition capital of Australia', when numerous historic public buildings were demolished (cf.Herde, 2022).As a result, Brisbane's architectural character exists largely within private housing stock (Lockwood, 1994).While Brisbane's postwar planning instruments have allowed multi-family dwellings, the area of the city where they are allowed has generally decreased over time (Lockwood, 1994).
The introduction of protections for character houses in Brisbane.By the early 1990s Brisbane's population had trebled from 502,000 in 1954 to over 1.4 million in 1991 (ABS, 2022).Momentum was also growing for the protection of houses constructed prior to World War II.A 1993 Brisbane City Council plan stated that the 'impact on our residential suburbs includes removal or demolition of ''Queenslanders'', erosion of the character of neighbourhoods by inappropriate new buildings and intrusion of non-residential uses into residential areas' (BCC, 1993: 16).Amendments to the Brisbane Town Plan 1987 were introduced in 1995 where some neighbourhoods were declared demolition control precincts, requiring an advertised planning application to remove or demolish a character house (Sommerfield, 2003).Bipartisan changes were incrementally introduced between 2005 and 2008 to refine protections for houses built before 1947 from demolition or removal, which had previously only been protected if they were in groups of three, and to introduce a minimum lot size of 450 m 2 to prevent subdivision of lots containing character houses (Falvey, 2007;Griffith, 2005).
At the same time, new planning instruments shifted the balance to infill development as the major source of new dwelling supply.Infill development ranges from large-scale master-planned high-rise developments to ad hoc subdivision of backyards for additional house construction (Gallagher et al., 2020).A state planning instrument mandates that 94% of new dwellings in Brisbane are to be sourced from the existing urban area (Department of Infrastructure, Local Government and Planning, 2017).It is, however, the local government planning scheme that specifically outlines how and where new dwellings are to be constructed.Both the 2000 and 2014 iterations of the Brisbane City Council planning scheme focussed on higher density development and mixed uses around existing railway and busway stations, but also increased protections for character houses.The Brisbane City Plan 2014 simplified provisions to allow owners to shift character houses and subdivide the vacant side of the lot.However, pre-1947 houses could only be demolished if 'structurally unsound' (BCC, 2021, section 8.2.21).
In the current iteration of Brisbane's planning scheme, development in the Character Residential Zone 'provides for low density suburban and inner-city living though the development of predominately 1 or 2 storey dwelling houses comprising of existing houses built in 1946 or before and infill housing that incorporates any housing built in 1946 or before in the development' (BCC, 2021, section 6.2.1.5).These policies preserve buildings based on a threshold house age, rather than specific architectural traits or social histories.Planning requirements for modifications are generally limited to site density, building height, number of storeys, setback and the appearance of fences and garages (BCC, 2021, section 8.2.22).This was an intended policy outcome, with Brisbane City Council's then Deputy Mayor making clear that regulations on renovating character houses should be eased, but demolition controls tightened (Falvey, 2007).Under Brisbane's planning scheme, character houses can be lifted and built under, extensions can be added, and the house can be moved so that the lot can be subdivided.However, any additional dwellings must be located between or behind character houses and of a similar scale (BCC, 2021, section 6.2.1.5).This effectively limits new development to detached houses or, where the planning scheme allows, low-set townhouses and apartments (BCC, 2019).Multi-family dwellings, referred to as 'multiple dwellings' in Brisbane's planning scheme, must be no more than two storeys, with a maximum dwelling yield of one dwelling per 300 m 2 in the Character Residential (Infill) zone (BCC, 2021, section 6.2.1.5).Character Residential zones began in suburbs within four kilometres of the city centre (Lockwood, 1994) but now account for 12.3% of Brisbane's residential zoned land area.In comparison, the low-density residential zone contains most residential zoned land (73.2%), with the remaining 14.5% distributed into higher density zones.
Data selection and analysis.To analyse the implications of preservation policies on redevelopment, we selected five study areas containing houses built before 1947, in both Character Residential and other zones.Each study area is located within 10 kilometres of Brisbane's city centre.Three (South Brisbane, Woolloongabba and Newstead) are adjacent to the city centre and two (Nundah and Indooroopilly) were identified as major centres in the Brisbane Town Plan 1987 (Figure 1).
We first collected the 1951 land use survey maps covering the five selected study areas from the Brisbane City Council's Library Services (BCC, 1951).These maps were compiled around 1950-1951 to determine the land use zones in the Brisbane Town Plan.The original key to the colour codes used in these survey maps was lost but the codes can be deduced by historical knowledge and verified using 1946 aerial photos.These aerial photos were also used by Brisbane City Council to determine which houses should be retained as part of their planning scheme.Using the 2021 digital cadastral database (DCDB) obtained from the Queensland Government Spatial Data Portal (Queensland Government, 2021) as the base map, we georeferenced the 1951 survey maps for the selected areas to the DCDB and added the land use information to each land parcel.We then scanned, georeferenced and digitised Brisbane's 1952 proposed zones, which guided council development decisions prior to a formal planning scheme being gazetted in 1965, and the Brisbane Town Plan 1987, to obtain the land use and zoning data for these times and assigned these data to each lot using the 2021 DCDB as the base map (Figure 2).
The 1987 planning scheme had three residential zones, with the Residential B applying to much of the inner city and the only zone where apartment buildings were allowed.Height limits varied depending on location and minimum lot sizes.In contrast, the Residential A zone -the predominant residential zone across the city at the time -expressly prohibited apartment buildings.
We collected contemporary zoning data in Shapefile format from Brisbane City Council's planning scheme (2021).Residential zones include the Character Residential, Low Density (houses only), Low-Medium density (building of up two to three storeys in height, depending on location), Medium Density (up to five stories) or High Density Residential (up to eight or 15 stories, depending on location).Contemporary land use data was  derived from the Queensland Land Use Mapping Program (2019).Land use types were standardised across the 1951 and 2021 datasets to use the same terminology to classify land uses.Across all time periods housing typologies were categorised as either a house, defined as a single-family, detached dwelling on a single lot, or multiple dwelling (apartment, townhouse and the like).Industry included manufacturing and warehousing, commercial services included offices and retail, and public services included schools and hospitals.
Using ArcGIS, we spatially joined the land use data in 1951 with zoning in 1952 and 1987 and land use and zoning in 2021.Through a series of queries in GIS based on the attribute features of each land parcel, we identified 5984 lots in the five selected study areas that contained a detached house (as per the property boundaries defined in the 2021 DCDB); their land use in 2021 and zoning in 1952, 1987 and 2021 were also recorded in the attribute table.This integrated dataset enables us to track the change (if any) of land use and zoning on each lot from 1951 to 2021.For example, a lot in South Brisbane was used as a residential dwelling (detached house) in 1951 but was zoned for industrial use in 1952.By 1987 this same lot was zoned for warehousing and, in 2021, the lot was zoned for high density residential use and contained an apartment building.Through this data we can track land use and zoning transitions for almost 6000 lots containing a house in 1951 and analyse how planning instruments influence redevelopment patterns.

Results
Our results provide insight into the implication of fluctuating urban policy trends, such as inner city, low density housing being earmarked for redevelopment in 1987 through the Residential B zone, and the introduction of character zoning in the 1990s, which protected remaining pre-1947 houses from removal (see Figure 1).Figure 3 provides a summary of the results, outlining changes to zoning (1952, 1987 and 2021) and land use (1951 and 2021) over time for the 5978 lots containing houses in 1951.
More flexible zoning prior to the 1980s facilitated the construction of apartments and other multiple dwellings.This was a policy change from the 1950s, where there was a clear intention of relocating residential dwellings away from inner city and riverfront areas and rezoning these houses to warehousing or industrial use.A focus on the redevelopment of inner-city areas occurred in the late 1980s and these properties were again rezoned but, in this instance, to mixed use or high density residential.By 2021, a large number of lots were used for commercial services (20.2%) or multiple dwellings (46.7%), with 28.6% of total lots containing a detached house.Using the Character Residential zones as an indication of where pre-1947 houses were retained, 1221 lots (20.4%) contained a character house protected from removal (Figure 3).While it cannot be assumed that all pre-1947 houses will be in Character Residential zones, this figure indicates that approximately four out of five pre-1947 houses were removed over the 70-year period.The introduction of character zoning in the early 1990s not only encouraged the retention of remaining character houses but also facilitated the construction of additional detached houses, as only a small number of multiple dwellings were constructed on these lots despite the zone allowing infill development.

Apartment zonings facilitate multiple dwelling construction
Our results show that in 1987, 3479 out of 5978 (58.2%) of the total lots were zoned as Residential B in 1987, which allowed for higher density residential development such as apartment buildings (Figure 3).This zone did not contain requirements for retention of pre-1947 housing.The majority of lots containing a multiple dwelling in 2021 were in the Residential B zone in 1987 (73.9% of the 2792 lots containing a multiple dwelling in 2021).A number of lots (584 or 16.8% of lots zoned as Residential B in 1987) were dezoned between 1987 and 2021, by having their allowable densities reduced through the requirement to retain a pre-1947 house.This indicates that a number of character houses remained in the study areas despite being zoned for apartment building construction until the early 1990s.There were 695 lots that contained houses in 2021 despite being in a zone that allowed multi-family housing.Allowable densities on these lots ranged from rowhouses to 15-story apartment buildings (Figure 3).This figure means that 40.7% of existing detached houses are not subject to retention requirements and could, in theory, be replaced with higher density housing.In fact, 302 lots containing houses could be redeveloped into apartment building of four stories or more, accounting for 12.9% of all lots in these higher density zones.

Small lot sizes prevent upzoning and redevelopment
The mean lot size in 1951 for the 5978 lots studied was 714.7 m 2 .For lots that were upzoned to Residential B (apartments allowed) in 1987, the mean lot size was 759.9 m 2 , compared to lots zoned as Residential A (houses only) which had a mean lot size of 568.5 m 2 .The mean size of lots in a zone allowing for apartments of five storeys or more in 2021 was 945.8 m 2 , compared to a mean of 690.7 m 2 for lots in a Character Residential zone.Across all zones, the mean lot size (in 1951) of a house that was preserved between 1951 and 2021 was 575.1 m 2 , whereas the mean lot size (in 1951) of a house that was converted into a multiple dwelling by 2021 was 880.9 m 2 .
Limited infill development in character residential zones.Of the 1707 lots that contained a detached house in 2021, following changes to heritage protection in the 1990s and 2000s, the majority (1221 lots or 55.0% of all lots containing houses in 2021) were in a zone that required retention of any house constructed before 1947 (Figure 3).Put simply, a two-bedroom, character house can be renovated and extended to become a house with five bedrooms, a two-car garage and two living rooms, but cannot be demolished.See Figure 3 for renovations in practice.The majority of these houses (1804 lots or 63.5% of all lots containing houses in 2021) had previously been zoned as Residential B in 1987 (allowing for apartment construction), indicating that a large number were dezoned between 1987 and 2021.We found that 177 out of 1087 lots (14.5%) in a Character Residential zone, allowing for additional dwelling construction, contained a multiple dwelling.

Discussion
Our results demonstrate that changes to urban policy have a definitive impact on the built environment by facilitating both redevelopment at higher densities and preservation of houses.Just 1.0% of lots that allow for medium to high-rise development still contain houses, whereas lots in a Character Residential zone had limited uptake in the opportunity to add extra dwellings, despite infill development being allowed.Given that the degree of modification to character houses allowed under the existing planning scheme (cf.BCC 2021, sections 6.2.1.5and 8.2.22), that the default position is protection from demolition or removal based on the age of the structure rather than specific architectural traits (cf.BCC 2021 section 8.2.21) and that the policy does not apply to all character houses in the city but to select areas based on neighbourhood zoning (see Figure 1), there are clearly exclusionary implications to this policy (Lemar, 2015).

Preservationist planning prevents housing diversity
Our results demonstrate that preservationist planning, in this instance, is synonymous with maintaining low residential density.One of the guiding principles for Brisbane City Council's planning strategy is to 'protect the Brisbane backyard and our unique character', which includes using planning instruments to prevent townhouse and apartment construction 'in areas for single homes', ensure minimum setbacks on property boundaries, and to seek 'greater enforcement powers. . . to protect Brisbane's character and values' (BCC, 2022).These principles were created following a survey of Brisbane residents.Where infill development in the form of multi-family housing is allowed, the planning scheme requires a maximum of one dwelling per 300 m 2 of site area (BCC, 2021, section 6.2.1.5).Our results show that even areas targeted for densification through infill development, character house retention requirements, combined with minimum lot sizes and maximum dwelling yields, preclude housing diversity.Where additional dwelling construction occurs, it is generally in the form of backyards being subdivided for additional house construction (cf.Gallagher et al., 2020).
Low levels of redevelopment imply that the existing use value of the character house is higher than the development value of adding new dwellings.The construction of new dwellings will not occur if the densities allowed are too low to make development economically feasible (Phillips, 2020).Research consistently finds that minimum lot sizes compel developers to build houses on lots larger than what the market would otherwise support (Gottlieb et al., 2012;Grey and Further, 2019), thereby increasing the cost of housing (Zabel and Dalton, 2011), exacerbating social segregation by adversely impacting would-be new residents and contributing to urban sprawl (Boudreaux, 2016).As the outcome of Brisbane's planning requirements to retain character houses suppress multi-family housing, we posit that the unstated aim of these planning instruments is exclusion (cf.Nally, 2022).

Small lot sizes protect character houses
Despite the assumed impacts of zoning, owners ultimately have agency in how land use changes (or does not change) (Acolin and Vitiello, 2018).Zoning does not decide whether construction will occur.Fundamentally, in a market-based economy, zone-based regulations determine what is allowed to be constructed and private actors, policy decisions (e.g. interest rates, subsidies to homeowners), and exogenous forces (e.g.migration, foreign investment) will determine if new structures are built.Due to preservation policies as well as minimum lot sizes, minimum car parking and setback requirements, new development in existing residential areas is largely limited to the construction of an additional detached house, which is often far below marketdetermined levels (Chakraborty et al., 2010).Our results indicate that character houses on larger lots were historically more likely to be rezoned for higher density, and, conversely, that lot size is a crucial factor in the conversion of pre-1947 housing.
Many of the lots containing multi-family housing in 2021 were in the Residential B zone in 1987.This zone allowed for walk-up apartment building construction, including the 'six-pack' apartment (see Figure 2).This housing typology has been historically highly stigmatised but is often of a similar size and bulk to contemporary Australian houses (CommSec, 2020).Where they still exist, these apartments provide affordable housing in some of Australia's most expensive suburbs (McGreevy, 2018).Previous research of one Brisbane inner city suburb in 1994 found that take-up of the Residential B zone was as low as 9.5%, meaning that most property owners chose to retain the original house despite the absence of character house retention requirements (Lockwood, 1994).This is supported by our research which shows that 695 landholders opted to retain a house on the lot, despite Character Residential zones not applying and zoning allowing a higher density use.Our results indicate that in the absence of Character Residential zones, many pre-1947 houses are likely to be retained by their owners.As such, widespread preservation requirements may not be required to conserve built heritage and could potentially be limited to areas of historical significance.The question therefore becomes whether the perceived benefits of conserving character areas, where the built environment is unable to transform, denser development is prohibited and the 'leafy green suburbs' are maintained (Fernandez and Martin, 2020: 3241), justify exclusionary zoning practices (Andersson et al., 2019;Koster and Rouwendal, 2017).
Preservationist planning is a form of exclusionary zoning.The imposition of zoning can be viewed as a contract between a landholder and the state, with landholders restricted in their ability to develop a property but benefitting from constraints imposed on neighbours (Sheehan and Kelly, 2015).The allocation of specific uses, such as low density residential, occurs at a point in time and informs current and future landholders of whether a proposed use is permissible (Sheehan and Kelly, 2015).Issues arise when knowledge of future needs changes, requiring changes to applicable zoning such as increases to density.Nelson (1979) argues that zoning represents the evolution of a collective property right, with the practical effect being the transfer of key rights from the individual to the municipality.Zoning provides residents with the right to collectively decide what new uses are permitted and that 'in the absence of zoning, more desirable neighbourhoods would lack protection from and would be occupied by less affluent individuals living in higher density facilities' (Nelson, 1979: 719).In fact, zoning in the post-war period has evolved to create a framework where owners have significant power to restrict growth and change (Glaeser, 2011), reflecting the inherent conservatism of existing residents (Glaeser, 2011).Glaeser (2011) states that there are two powerful psychological biases behind this perceived need to protect neighbourhoods from redevelopment or change, the first referred to as 'status quo bias' where a person has a 'strong attachment to the current state of affairs' and the second, where people 'significantly over-estimate the impact that a negative shock will have on their happiness' (p.262).
There is a balance to be struck between redevelopment and preservation, particularly as more flexible zoning leads to greater housing diversity.In Brisbane, residents have called to extend Character Residential zoning to suburbs where Brisbane City Council proposed increases to residential density (cf.Nally, 2022), but residents in the same neighbourhood oppose heritage listing of their houses due to the restrictions on modifications (cf.Formica, 2023).Most residential land in Brisbane is zoned for single family houses (but not character housing) and these neighbourhoods are car-centric and lack mass transit.In comparison, inner city neighbourhoods with character housing are well-serviced by railway and busway stations, as well as significant commercial precincts.A study of Adelaide, Australia saw that wealthy inner suburbs that did not have exclusionary zoning until the 1980s had a greater diversity of housing typologies (and therefore more affordable housing) when compared to less expensive suburbs with homogenous, low-density housing due to the path dependant legacy of restricting multiple dwelling construction (McGreevy, 2018).This is evidenced in our study areas, which, due to the legacy of the Residential B zone, contain walk-up apartments and townhouses constructed in this period.Despite infill development provisions allowing for the construction of townhouses and walk-up apartments in some character areas, previous research shows that subdivision of lots for the construction of additional detached houses was the most common form of densification in Brisbane's inner-city suburbs (Gallagher et al., 2020).This is supported by our research which shows a limited uptake of opportunity to increase the diversity of housing typologies in these neighbourhoods.
Decisions to terminate preservation requirements can be taken to increase housing density and improve affordability (Fernandez and Martin, 2020).In adopting a new planning scheme in 2016, Auckland (New Zealand) terminated the preservation requirements of 30% of previously protected areas.Properties in New Zealand's character protection zones have controls on the demolition or alteration of existing buildings, and the design and appearance of new buildings, with most dwellings limited to use as a detached house.The main impetus of this decision was to improve housing affordability through greater housing diversity (Fernandez and Martin, 2020).While the removal of character protections zones did increase price premiums for upzoned lots, Fernandez and Martin (2020) concluded that this was due to land eventually being directed to its most valuable state, which includes redevelopment at higher densities.
Nevertheless, reform of existing zoning, especially in cities with high housing demand, can also drive gentrification and fail to produce housing for low-and moderate-income earners if efforts to ensure affordable housing provisions are not supported (Chakraborty, 2020).

Conclusion
Preservationist planning imposed through planning instruments aims to conserve the historical value of individual dwellings, and neighbourhoods.In the case of Brisbane, Character Residential zones restrict the development of multi-family housing and, without these preservationist policies, many character houses are nonetheless preserved on smaller lots.We argue that policymakers should be cautious of extending preservationist policies across a local government area, without due diligence paid to the expected versus intended outcomes and impacts.There is an argument that preservation should be a targeted policy affecting properties with specific architectural or social history traits, especially if the underlying impetus of conservation is not to limit housing diversity.

Figure 1 .
Figure 1.(a) Extent of the Character Residential zones compared to other residential zones in Brisbane in 2021.(b) Character Residential zones in the study areas in 2021.(3) Lots containing houses in 1951.

Figure 2 .
Figure 2. Transformation of character houses in Study Area 3.

Figure 3 .
Figure 3.The process of land use and zoning changes of 5978 lots containing detached houses in 1951, showing the rezoning of 3479 lots for apartment building construction (Residential B) in 1987, and 2792 lots containing apartments, townhouses, or other multi-family dwellings in 2021, and 1707 lots containing houses in 2021.Attributes for each lot includes (1) land use in 1951, (2) land use zoning in 1952, (3) land use zoning in 1987, (4) land use in 2021 and (5) land use zoning in 2021.