In the area of public building law, the legislative competence lies with the states, insofar as the German Constitution

Grundgesetz für die Bundesrepublik Deutschland (GG) in der im Bundesgesetzblatt Teil III, Gliederungsnummer 100‑1, veröffentlichten bereinigten Fassung, das zuletzt durch Artikel 1 des Gesetzes vom 19. Dezember 2022 (BGBl. I S. 2478) geändert worden ist.

German planning law distinguishes between three areas in which buildings can be constructed: the (fully or partially) planned area (§30 BauGB), the unplanned inner area (§34 BauGB) and the unplanned outer area (§35 BauGB). A clear distinction must be made between the different unplanned areas, as the inner area may be built upon under certain conditions while the outer area is to be kept free of any building development as a matter of principle.

The amendments to the Baulandmobilisierungsgesetz are intended, on the one hand, to create opportunities to make land available for housing construction more quickly or efficiently, e.g. by extending the possibilities for exemption from development plans and making it easier to build in inner and outer areas. On the other hand, the development of previously unused areas is to be promoted. This is done primarily by expanding the scope of the application of municipal pre-emption rights and the building order for areas with tight housing markets.

Some of the amendments in the Baulandmobilisierungsgesetz aim to facilitate or accelerate the possibility of building and thus have an effect at the usage rights level. Other regulations, however, are intended to promote physical construction and thus have affect disposal rights. The most important innovations of the Baulandmobilisierungsgesetz – differentiated according to their effect level – are presented below.

The following innovations concern both the planned and unplanned inner area as well as the unplanned outer area and are intended to make it easier to mobilise building land.

The following innovations are intended to strengthen the actual land mobilisation by the municipalities.

The Baulandmobilisierungsgesetz aims to strengthen the municipalities’ abilities to activate building land more quickly and secure affordable housing, thus counteracting the tight housing market in German cities. It is questionable whether this has been achieved with these amendments.

The new regulations focus on measures that purely impact usage rights and have little or no influence on the physical development of the land. In addition, the amendments often only affect individual cases, such as the amended exemption options under §31 para. 2 and 3 BauGB. The new regulations with an effect on disposal rights, on the other hand, are only selectively related to individual detailed aspects. The amendments to the pre-emption rights in §§24, 25 BauGB expand the existing legal options of the municipalities. Still, it is questionable whether they can help ease the situation in the housing market since they are purely reactive instruments and the municipalities cannot act on their own initiative (Kment 2020: 181).

The amendments to the building order (§176 BauGB) expand the regulation’s field of application, but the extent to which they can make a real contribution to the mobilisation of building land remains to be seen. Even in previous planning practice, the building order did not play a significant role, as it was considered too “complicated and court-heavy” (Parzefall 2020: 27), a “blunt sword” (Krautzberger/Stüer 2021: 37) with too many obstacles to enforceability.

In summary, it can be said that apart from new possibilities to improve buildability, there are still hardly any instruments available to enforce physical development. It remains to be seen whether the legislative changes listed here can fulfil the legislators’ intentions. The Building Land Mobilisation Act currently seems to be only one step on the long way to effective building land mobilisation.

Since 1969, spatial planning has been explicitly listed in the catalogue of state responsibilities in the Swiss Constitution (BV).

Bundesverfassung der Schweizerischen Eidgenossenschaft (BV) vom 18. April 1999, Stand am 13. Februar 2022.

The main body of federal law is the 1979 Spatial Planning Act (RPG) and the principle of separation contained therein, i.e. the division of land into the building zone and the non-building zone. The former can be further differentiated by cantonal law, while the latter is conclusively regulated by federal law (Hänni 2016: 255; Griffel 2017b: 58, 137). In the building zone, there is freedom to build, although a building permit is required upfront to ensure conformity with planning and building law (Aemisegger/Moor/Ruch et al. 2016a: 289). In the non-building zone, there is no freedom to build as long as there is no explicit exception under federal law (e.g. for agricultural buildings, infrastructure, or other place-related issues) (Griffel 2017b: 22). In addition, the main procedural instruments for planning within the building zone are predefined in the Spatial Planning Act, such as the structure plan (usually at the cantonal level) and the zoning plans (usually at the communal level). While the structure plan is only binding for the authorities, the zoning plans are directly binding for the owners: thus, they form the legal basis for building permits (Aemisegger/Moor/Ruch et al. 2016b: 65). The federal government merely lays down abstract conditions about which aspects must be considered in zoning planning. The concrete decision is the responsibility of the municipalities.

The system aims to legally define the limits and restrictions on the owners’ land use (Berisha/Cotella/Rivolin et al. 2021: 195). The actual implementation of construction work is a decision made by the owners. In this respect, the system is passive (Hengstermann 2019). Building use of the land is made possible and the corresponding incentives are created. However, the planning authorities cannot guarantee the physical implementation of building work, so the property owners have a veto. Despite the economic incentives, considerable areas remain unused or underused, even in high-priced locations. Precise quantification is difficult, but estimates suggest that Switzerland’s building land reserves could provide additional housing for 0.7 to 1.94 million inhabitants (Nebel 2014: 146). However, if the development pressure is instead met by expanding the building zone, then this will result in precisely those sprawling spatial structures that contradict the constitutional goals and the entire political legitimacy of spatial planning. Promoting the mobilisation of building land thus serves the achievement of objectives and is not only sensible in planning terms but legally required.

However, the fact that the system does not work so effectively in everyday political life became clear to politicians and the electorate through the so-called Galmiz case (Hengstermann/Gerber 2015). Although the planning and nature conservation regulations stipulated otherwise, a 55-ha area in the municipality of Galmiz in the canton of Fribourg was zoned to enable an industrial development to satisfy economic policy. The procedure is questionable for legal reasons. Politically, however, it shows the weakness of spatial planning: the planning system cannot prevent urban sprawl if it primarily tries to prevent external development (negative planning) (Koll-Schretzenmayr 2021). What is needed is effective inner development (positive planning), which requires assertive spatial planning and instruments for mobilising building land. This realisation is the main motive behind the partial revision of the planning law (so-called RPG1-reform), which the Federal Assembly enacted in 2012, which was approved by the electorate in 2013 with 62.9 % in favour, and which entered into force on 1 May 2014.

The RPG‑1 reform aims to increase the effectiveness of spatial planning. In addition to Article 8a RPG (cantonal planning) and Article 5 RPG (compensation for added value) (Hengstermann/Scheiwiller 2021), Article 15 RPG (building zones) was reformed as well. This contains the federal requirements for the local planning authorities (usually the municipalities). However, it is also indirectly essential for property owners, as it determines which building zone their property belongs to and thus whether it can be built on.

In the old version, Article 15 RPG included three criteria that must be fulfilled for land to be eligible to be assigned to the building zone by municipal planning (so-called zoning). The land must be suitable, be serviced by the municipalities within the next 15 years and be expected to be needed within the same period (Art. 15 para. 2 RPG old version). In comparison, the new wording of the same article includes further quantitative and qualitative general principles of the building zone (Art. 15 para. 1, 2, 3 and 5), as well as five cumulative criteria under which conditional land can be newly assigned to the building zone (see Table 1).

The quantitative dimensions of the building zone must (as in the old version) be based on the anticipated demand for the subsequent 15 years (Art. 15 para. 1 RPG). If the existing building zone already exceeds this anticipated demand, there is now an obligation to reduce it (Art. 15 para. 2 RPG) (Huser 2019: 107). In addition, the calculation of this requirement is regulated in detail and made binding in the form of a technical guideline (Art. 15 para. 5 RPG). The municipalities are also explicitly bound by planning law requirements regarding the quality of the building zone (Art. 15 para. 3 RPG). Explicit reference is made to the binding conformity with the objectives and principles of planning (Art. 1 and 3 RPG). In addition, the principle of functional, i.e. cross-border planning, applies (Art. 15 para. 3 RPG) (Aemisegger/Moor/Ruch et al. 2016a). Taken as a whole, these new regulations result in the general principles of building zones being defined much more precisely (Griffel 2017b). They also result in legally binding framework conditions within which municipal zoning must take place.

Since the reform, five cumulative criteria must be fulfilled when assigning land to the building zone (Art. 15 para. 4 RPG): (i) suitability, which refers to both technical and legal aspects; (ii) need, servicing and development within the next 15 years; (iii) the reservation that cultivated land is not fragmented; (iv) the legal guarantee of actual availability; and (v) compliance with the requirements of the structure plan. With this catalogue of criteria, the federal legislature has now given the municipalities more precise guidelines for their spatial development, which they must translate into binding specifications for the type and extent of permissible building use of land.

Overall, the density of land-use regulations has increased significantly. While Article 15 RPG in the 1980 version served to provide an initial, nationwide, uniform definition of building zones, the cantons now have significantly more precise requirements under federal law regarding the quantity, quality and conditions for expanding the building zone. The cantons’ scope for interpretation (e.g. the interpretation of the anticipated demand) and legal loopholes (e.g. the compensation of planning-related added value) have been reduced as a result, even though this can lead to an increase in requirements and considerable additional expenditure in local planning practice.

The RPG‑1 reform also includes new provisions that affect the level of disposition law. For example, actual availability is explicitly mentioned in Article 15 RPG for new building zones and is even extended to old building zones with the contemporary Article 15a RPG.

The aforementioned legally binding cumulative criteria for expanding the building zone also include actual availability (Art. 15 para. 4 lit. a and d RPG new version). First, the technical and legal suitability of the land for building on (Art. 15 lit. b RPG old version) is adopted from the old regulation as a mandatory criterion. In addition, it is now compulsory that the land is needed, serviced and built on within the next 15 years (Art. 15 para. 4 lit. b RPG new version). In this list, the legislator thus adds a “de facto building obligation” (Hengstermann/Gerber 2017) to the existing infrastructure service obligation and the anticipated need. Accordingly, municipalities must legally ensure that the land they want to assign to the building zone is actually built on. They must also legally ensure this outcome (Art. 15 para. 4 lit. d RPG new version), which can be achieved through general building code regulations or individual contracts with the landowners. The latter means linking zoning decisions to the consent and contractual agreement of the landowners. The concrete building intention, schedule and consequences in the event of non-occurrence are then laid down in the contract. If applied, the legal consequence is most often the takeover of the land by the municipality so that the implementation of the zoning plans is also ensured, under the law of disposal if necessary.

All in all, these two regulations (Art. 15 para. 4 lit. a and d RPG new version) mean that in addition to the rights of use, the zoning process now also includes deadlines with an obligation to use the land, thus preventing future building land from being hoarded. If physical development does not occur within the time limit, the original zoning becomes null and void. It is thus withdrawn without compensation (non-zoning) or the land is taken over by the municipality at the general market value (expropriation) and used for development.

Not included in the provisions of Article 15 RPG is building land under the old law, i.e. land that had already been assigned to the building zone when the partial revision came into force in 1980. To promote the availability of this land, the legislator has added the new Article 15a RPG and established two essential mechanisms in the process. The article states: “The cantons shall work with the communes to take the measures that are required so that building zones are used for their assigned purpose” (Art. 15a para. 1 RPG new version). Apart from a reference to building land readjustment (according to Art. 20 RPG), the concrete measures are not defined. Moreover, the idea of a building obligation is also taken up. Accordingly, the cantons must enact concrete, applicable regulations with which building obligations can be imposed (Art. 15a para. 2 RPG new version) (Hengstermann/Gerber 2017: 16–17). Compared to Article 15 RPG, the provisions in Article 15a RPG are thus much more abstract and formulated as performance-based regulations (Hartmann/Albrecht 2014: 246–248). There is no direct applicability of federal law (Griffel 2017a: 30–32). Instead of the basic competence of the Confederation, the legislator has instead specified binding objectives in Article 15a RPG which the cantons must achieve. The exact way in which the objectives are accomplished remains within the decision-making competence of the cantons.

Similar to the German Building Land Mobilisation Act, the partial revision of the Spatial Planning Act with several regulations aims to ensure actual availability of building land. In contrast to the German law reform, however, the political motivation lay less in creating affordable housing. Instead, the legislative reform was legitimised with the goal of reducing the conversion of agricultural land via effective inner urban development and ultimately putting a stop to urban sprawl.

The reform is characterised by new regulations that affect both the level of land-use law and the level of land disposal law. The federal requirements that affect land-use law were specified to enable the municipalities (as primary planning authorities) to allow inner development through stipulating land use. In addition to this traditional planning approach, the Swiss reform took into account the dimension of disposal rights (property rights) for the first time. To ensure physical development, availability was included as a mandatory criterion for new zoning and a de facto building obligation was also introduced. In addition, a binding legislative mandate was formulated so that the cantons can use further measures to promote the availability of building land governed by the old legislation.

In order to ensure output-legitimacy, the democratic decisions concerning future settlement development should not be made impossible by the veto of individual property owners. Accordingly, the reform is to be understood as an essential step from pure land-use planning, which relies on the possibility of building during the implementation of the plan, to a land policy that also takes property rights into account (Hengstermann 2019). Ultimately, this also includes the intensified implementation of spatial planning using instruments under private law, such as civil law building rights (Gerber/Nahrath/Hartmann 2017: 1699–1700).

In both Germany and Switzerland, it can be observed that spatial planning and land policy have received increased political attention, which has ultimately led to remarkable legislative activities. In both countries, the relationship between increasing housing supply and simultaneously reducing land consumption is of central importance and represents the factual problem definition in both cases. However, the individual priorities differ in the two countries. In Germany, political activities are mainly legitimised by public debates on the provision of (social) housing. Although many of the measures also aim at inner development (e.g. §176a BauGB as a masterplan for the promotion of inner development; see Spannowsky/Uechtritz 2022: 1846–1848) and the reduction of land consumption is a clear political goal (Deutscher Bundestag 2020: 22), the expert discussion on these points takes a back seat to the housing issue.

In Switzerland, this relationship is reversed. The protection of land against urban sprawl is the dominant political motive, while at the same time the provision of housing is discussed only in certain areas (among the professional public and in some Swiss cities). However, the different discursive starting points lead to a similar challenge for the planning systems in both countries: the difficulty of mobilising the corresponding land demand for inner development.

In their concrete legislative activities to improve the availability of building land, the two legislatures initially proceeded similarly, focusing on enhancing the provisions affecting the usage rights. The German Baugesetzbuch amendment contains a whole series of such regulatory changes creating, for example, the possibility of an exemption from the provisions of the development plan in favour of housing construction (§31 para. 3 BauGB), the option of drawing up a sectoral development plan for (social) housing construction (§9 para 2 lit. d BauGB), and the extension of the regulation on development in the outer area (§13b BauGB). In Switzerland, the provisions on the building zone were concretised (Art. 15 RPG) by introducing qualitative and quantitative principles and cumulative criteria for the expansion of the building zone.

It is noticeable that the weighting of provisions affecting disposal rights varies considerably in the legal reforms. The German legislator has attempted to increase the practical applicability of two instruments affecting disposal rights: the municipal right of pre-emption and the building obligation. For this purpose, the legal description of the cases of applicability has been expanded, particularly by explicitly listing the need for housing as a public interest and by listing unused and underused land as the application’s object. In both instruments, however, the new regulations only tackle some of the obstacles witnessed in planning practice, so it remains to be seen whether application of the instruments will actually increase. The Swiss legislator has attempted to enact much more far-reaching disposal rights provisions that guarantee the actual development of land suitable for planning purposes. The provisions are intended to prevent future undesirable developments and correct past undesirable developments retroactively. In the former case, detailed provisions have been enacted which suggest that spatial planning can effectively prevent urban sprawl in the future. Therefore, the individually justified possibility of building on a plot of land is linked to a publicly justified obligation of use – with corresponding restrictions under disposal rights in case of non-compliance.

The retroactive provisions are politically ambitious but legally much less detailed. Here, Article 15a RPG constructs a far-reaching planning competence but merely formulates a binding legislative mandate for the cantons with a building obligation and further measures.

In comparing the two approaches, it can thus be stated that both legislatures pursue similar planning policy goals but choose different focal points for the legislative mechanisms. The changes in German law aim to promote the mobilisation of building land by simplifying the buildability of areas suitable for development from a planning perspective. The changes in Swiss law also aim to promote the mobilisation of building land by increasing the owners’ willingness to build or by presenting regulations that ensure actual development if there is no willingness to build.

These differences are profound in terms of planning theory. They can be related to two differences between the German and Swiss planning systems despite all their similarities.

Municipalities in both countries are probably the essential public planning authorities. However, their political position and respective property owners differ, partly due to different planning law requirements. In Switzerland, zoning plans are revised when conditions have changed significantly (usually every 15 years) (Art. 21 para. 2 RPG). It is possible to politically re-debate past planning decisions and make different decisions – by rezoning and dezoning for example. In this respect, the municipality has a firm negotiating position every 15 years or so from which to find a suitable solution with the owners – or expressed in planning theory terms: to bring land-use planning in line with property rights. In Germany, this possibility does not exist in the same form (Feiertag/Schoppengerd 2022). After a plan is issued in the first place, there is no longer a regular review of the zoning.

The German planning system is based on the pure provision of development options (right-of-use level), as the coupling of planning policy plans and private law intentions is fundamentally prohibited (prohibition of coupling). Apart from some pragmatic solutions (e.g. by using urban development contracts according to §11 BauGB or strategic instruments like the urban development measure according to §§165-171 BauGB), the municipality cannot discuss the realisation of buildability with the owners. The German legislator has reacted to this situation by increasing the flexibility of the regulations. Thus, the plans themselves are not reformed, but they do allow reformed land uses. In contrast, the Swiss legislator has stuck to rigid instruments and developed a kind of coupling requirement. Following the primacy that the democratically determined plan needs to be implemented, public law and private law provisions are to be harmonised. The expansion of the building zone only makes sense in planning terms if the availability of the land is legally guaranteed, and only then is it lawfully permissible. Such a coupling has not been compatible with German planning law (§56 para. 1 p. 2 VwVfG).

Verwaltungsverfahrensgesetz in der Fassung der Bekanntmachung vom 23. Januar 2003 (BGBl. I S. 102), das zuletzt durch Artikel 24 Absatz 3 des Gesetzes vom 25. Juni 2021 (BGBl. I S. 2154) geändert worden ist.