All appeals are dismissed.

The costs of appeal are assessed against the Defendants.

The grounds of appeal are examined.

1. The Act on the Ownership and Management of Aggregate Buildings, which prohibits a sectional owner's right to use a site and a disposition of separation of a section for exclusive use, (amended by Act No. 3725, Apr. 10, 1984; hereinafter referred to as "Aggregate Buildings Act

B) Article 20 of the Aggregate Buildings Act is effective to dispose of a right to use a site separately from his/her section of exclusive ownership before the application of the provision of Article 20. Since Article 20 of the same Act is effective to dispose of a right to use the site, Article 20 of the same Act does not retroactively apply to the section of exclusive ownership before the application of Article 20, and if the right to use the site was disposed of separately from the section of exclusive ownership before the application of Article 20, such disposition shall not be deemed null and void as it violates the unity of the section of exclusive ownership and the right to use the site (see, e.g., Supreme Court Decision 2010Da7279, 72786, Jan. 27, 201). Meanwhile, since the right to use a site, which is prohibited from a separate disposition under Article 20 of the same Act, has a right to the site of a building for the purpose of owning the section of exclusive ownership, a person other than the sectional owner, regardless of the ownership of the section of exclusive ownership, has not been subject to restrictions on separate disposal under Article 20.

2 AD sold a corridor and rooftop in proportion to the selling area among the co-owned parts of the building of this case, Gangnam-gu, Seoul, the site of the building of this case at the time of the sale, and the common part of the building of this case. However, the above underground floor AE and the land of this case, among the above underground floor AE and the land of this case.