Section 2 of the Horizontal Property Law (49/1960) Act provides for its scope
This Act shall apply to:
a) Commonhold land formed in accordance with the provisions of section 5 (Communities which have commonhold community statement ‘Escritura de obra nueva y division horizontal’)
b) Commonhold land fulfilling the requirements established in section 396 of the Civil Code and for which no commonhold community statement has been filed. In any case, for matters relating to the legal system of ownership of private units and common parts, and for those regarding reciprocal rights and duties of commonholders, these commonholds shall be regulated by the provisions of this Act.
Where there are common parts (even just a swimming pool) owned by more than one individual such as your swimming pool the Act shall be applied and no owner can opt out
Section 23 of the Act 49/1960 provides for the termination
The commonhold shall terminate:
(1) By the destruction of the building.
Notwithstanding any covenant to the contrary, destruction shall be deemed to have occurred when the cost of rebuilding shall exceed fifty percent of the value of the property at the time the event occurs; unless the excess of the aforesaid cost is covered by insurance.
(2) By conversion to ordinary ownership or co-ownership.
Commonholders may choose to terminate their community and bring the commonhold to an end. They may choose to do so for whatever reason provided that unanimous consent is obtained.
Voluntary liquidation is a way of collapsing the commonhold back into ‘ordinary ownership or co-ownership’ regulated by section 392 onwards of the Civil Code.
A commonhold also terminates where all the units become owned by one proprietor, or where all common parts vanish. In the latter case section 392 onwards of the Civil Code shall not apply because there is no co-ownership