The distinction between chattel and land (realty) is firmly established in Common Law. It was best set out bySir John W. Salmond, former Solicitor General of and Supreme Court Judge in NZ, who in 1902 wrote Jurisprudence.

In §155. Movable and Immovable Property, Salmond explains the elements of immovable property (i.e. land):

Among material things the most important distinction is that between movables and immovables, or to use terms more familiar in English law, between chattels and land. In all legal systems these two classes of objects are to some extent governed by different rules, though in no system is the difference so great as in our own …

5…all objects placed by human agency on or under the surface with the intention of permanent annexation. These become part of the land, and lose their identity as separate movables or chattels; for example buildings, walls and fences. Omne quod inaedificatur solo cedit [Everything which is erected on the soil goes with it] said the Roman Law. Provided that the requisite intent of permanent annexation is present, no physical attachment to the surface is required. A wall built of stones without mortar or foundation is part of the land on which it stands. Conversely, physical attachment, without the intent of permanent annexation, is not in itself enough. Carpets, tapestries, or ornaments nailed to the floors or walls of a house are not thereby made part of the house. Money buried in the ground is as much a chattel as money in its owner’s pocket.

Footnote 2: Unlike a chattel, a piece of land has no natural boundaries. Its separation from the adjoining land is purely arbitrary and artificial, and it is capable of subdivision and separate ownership to any extent that may be desired. 

Salmond’s footnote 2 is most helpful. Land has no natural boundaries. Land as property is an arbitrary and artificial construct of society. A mobile home has a natural boundary.