Facts
On 19 February 2018 the Municipality of Samedan granted respondent [D.] the building permit for the demolition of an existing residential building (main usable floor area 125.10 m2) and the construction of two residential buildings with an underground garage on parcel 1423 (residential zone 1). The northern residential building (430.95 m2) was subject to a use restriction 'primary residence' within the meaning of Art. 7 para. 1 lit. a SHA, while the southern residential building (159.58 m2) was approved without a use restriction. The objection of the heirs of [A.A.] sel. was dismissed.
The heirs appealed to the Administrative Court of the Canton of Graubünden, which dismissed the appeal on 12 July 2019. Against this decision, the heirs (appellant 1, objector and owner of the adjoining parcel 1418) and the Federal Office for Spatial Development (ARE) appealed to the Federal Supreme Court on 16 September 2019. Appellant 1 requested that a use restriction be entered in the land register for the southern residential building, or alternatively that the matter be remitted; the ARE requested that the building permit be refused. The Municipality of Samedan waived its response, and the respondent requested dismissal.
The question in dispute was whether a use restriction was required for the southern residential building, given that the share of second homes in Samedan undisputedly exceeds 20%. The lower court held that the dwelling could be approved without a use restriction, as it was a legacy-law dwelling that could be reconstructed within the main usable floor area and extended by up to 30%.
Considerations
The Federal Supreme Court joined the two proceedings 1C_478/2019 and 1C_479/2019, as they concern the same decision and the same building application. The appeals were deemed admissible (Art. 82 lit. a, 86 para. 1 lit. d, 89 para. 1 and para. 2 lit. a, 90 FSCA; Art. 10 para. 1 SHO).
Based on the wording, systematic structure and legislative history of Art. 11 SHA, a cumulation of reconstruction and extension of legacy-law dwellings is inadmissible. Art. 11 para. 2 SHA permits reconstruction only 'within the previously existing main usable floor area', whereas para. 3 provides, as an exception, for an extension of up to 30% only for legacy-law dwellings. If an extension were also permitted for reconstructions, the restriction in para. 2 would serve no purpose. The materials (Message FF 2014 2287 ff.; AB 2014 962-964) show that the legislature intended the 30% extension only for the preservation of existing buildings, not for demolition and reconstruction.
An extension to reconstructions would also contravene Art. 75b para. 1 Cst., which limits the share of second homes to 20%. Since the 20% share has already been exceeded in Samedan, any extension of second-home floor area runs counter to the constitutional objective. The densification of spatial planning invoked by the respondent does not justify a different interpretation, as the prohibition on additional dwellings in the case of extensions in any event prevents genuine densification, and primary residences remain possible at all times. Nor can the result be achieved through staggered construction steps (first extension, later reconstruction), since a dwelling extended after 11 March 2012 may only be reconstructed to its earlier extent.
By contrast, combining an extension of legacy-law main usable floor area with the creation of new primary residences subject to a use restriction is permissible (Art. 7 and Art. 11 para. 4 SHA). Only the extension of legacy-law dwellings together with a new, unrestricted…