I can only speak for the Catholic Church. My next door neighbor is a Catholic priest and according to him:
A church is commissioned/decommissioned. The same term as used for many other types of buildings when they are taken in use for a particular purpose.
The act of commissioning a church requires the church to be made "Holy Ground". This involves a number of church rituals and is called the "Consecration" of the church. Consecrate/consecration can also be used as a verb and noun, and is often done so as an alternative to commissioning/commission, but it is not quite the same thing. An unused church which is still Holy Ground can be re-commissioned without the need for a Consecration.
In order to decommission a church, it is not really required to de-consecrate it. It is sufficient to stop using it as a church, but it will remain Holy Ground, until something takes place that de-sanctifies the place. (E.g. a serious act of desecration. Minor vandalism, like kicking over a tombstone in a graveyard, isn't enough. Having sex on the altar would do it. This actually happened in 2017 in a church in The Netherlands.)
There is also a church procedure to remove the Holy Ground status if desired. This is typically done if it is known in advance the place is going to be re-used for a purpose that is clearly at odds with its former usage as Holy Ground.
If a church is de-sanctified (lost its Holy Ground status) it needs to be re-consecrated before it can be used as a church again.
This is more involved than the regular consecration ritual as it consists of 2 parts: Removing the "evil" stain that de-sanctified it (making it neutral ground again) and then the normal consecration procedure.
P.S. Same thing applies to chapels and graveyards.