CG70205 | Land: what is land?
From HM Revenue & Customs · Capital Gains Manual
In law, land includes:
all buildings situated on it;
all fixtures attached to it;
any minerals below its surface; and
the air space above it.
However, there are specific provisions regarding;
treasure (owned by the Crown);
certain minerals (for example, all coal is owned by the Coal Authority and all gold and silver right are held by the Crown);
rights of passage for aircraft; which restrict the owner's rights over the land.
However the general rule that land includes all the buildings situated on it is over-ridden for certain CGT purposes:
roll-over relief, TCGA92/S155, see CG60281
receipt of compensation and insurance money applied in restoring the asset, TCGA92/S23 (6), see CG15742
assets lost or destroyed or of negligible value, TCGA92/S24 (3), see CG15773.