Although the extent of the natural right of support for land from a neighbouring tenement is not affected immediately either by excavations upon the land or by buildings erected on it, or by the excavations of others on adjoining land, yet after the lapse of a sufficient time easements may be acquired for the support of the land in its altered condition, and for buildings on it.

Besides the easements for special support in excess of the original natural right, an easement of the opposite kind is sometimes created which gives to the dominant owner a right to take away support in excess of his natural right, so as to leave surface land unsupported. This kind of easement is not uncommon in some mining districts, where owners of minerals would be seriously restrained in the exercise of their natural right to remove coal and some other minerals if they were under continual obligation to maintain adequate support for the surface.

Any of these easements may be acquired by grant, express or implied.

It is not necessary here to discuss express grants. Such grants to create or transfer easements must be by deed, and the deed should sufficiently indicate and describe what is granted or what is reserved by covenant.

A more common means by which easements of support, like many other easements, are acquired, is by implication when real property is transferred.

When an owner of land with buildings sells any of the buildings, either with or without the land on which they stand, there is an implied grant of support for the buildings sold, which is binding upon the lands of the vendor and any other person deriving title from him. The vendor has, of course, no power to bind or impose burthens on lands or buildings other than his own, so that if he sells a new building recently erected near the margin of his land, the easement thus created by implied grant at the time of sale may protect the building against removal of support subjacent and adjacent on one side, while an owner of land on the opposite side may remain free to excavate his land at short distance from the building so as to jeopardise its safety without being liable for any consequent injury to the building.

The same principle of grant by implication arises when an owner of several adjacent houses sells the houses separately to different purchasers. If the houses have been in any way dependent upon each other for lateral support they will be affected with easement rights and obligations after the purchase and sale, the owner of each house being servient to his adjoining neighbour for lateral support. The rights and obligations thus created will be reciprocal. The owners of the houses must not in such cases excavate to such an extent or in such manner as to endanger the stability of the houses adjoining, and will be liable for any injury which may be caused to the adjacent neighbours as a consequence of such weakening of support by excavation or any other means. When land is granted for building purposes an easement right for support of the buildings after erection is impliedly granted. The easement for support of buildings may spring into existence directly the land is sold for building purposes. The vendor must not so weaken support for the land sold that buildings such as were contemplated at the time of sale could not be safely erected on the land sold, any more than the vendor could be allowed to jeopardise the safety of the buildings after erection by taking away the requisite support.

The general rules applicable to all ordinary cases where an owner of land sells part of it may perhaps be safely formulated thus. Whenever an owner sells part of his land or buildings there is an implied grant (binding upon him and his successors in title to whatever part is reserved) of such extent of easement right as is necessary to give full effect to the grant and secure full enjoyment for the grantee of what is intended to be bought and sold.

If an owner sells land for ordinary agricultural purposes, reserving right to minerals below the surface, the vendee takes the land subject to natural rights of support for the surface in the state in which it exists at the time of purchase, together with right of support for any buildings which may have been on the surface at the time of purchase.

New heavy buildings he can only erect on the land at his own risk, unless he makes prior arrangements with the owner of the subjacent minerals. Otherwise he may not only incur the risk of injury to his house, but may also be liable for injury to subjacent mines and minerals.

If a man sells houses, he must be taken to grant impliedly all manifest easements relating to the houses sold, and he can have no right subsequently to deprive those houses of support unless he has preserved such right by express reservation at the time of sale, or acquired it by regrant or other legal means after the sale.

When the owner of land sells the minerals and reserves for himself the surface, then (on general principles, and in the absence of any express covenants relating to the matter) the grantee of the minerals will be prima facie entitled to take them all away without being under obligation to support the surface.

When surface and mineral rights are severed by Act of Parliament, or by other means than voluntary grant, presumption based on the theory of implied grants would ordinarily be excluded, and separate owners would be left in the enjoyment of their natural rights, except so far as they might be altered by Act of Parliament. Railway companies, for example, are made subject by Acts of Parliament to special laws enacted in their behalf, and in behalf of those persons whose lands have been acquired by the companies for the purpose of making railways.

Ordinarily railway companies acquire by purchase surface land only, and not underlying minerals ; but when the removal of minerals from below a railway line might be likely to cause injury to the surface the company, under terms and conditions specified in the Lands and Railway Clauses Consolidation Acts of 1845, may cause the working of the mines to be stopped and compensate the owner of the minerals for all loss.