Leviticus 27:13-15

13But if he wants at all to redeem it, then he must add one-fifth to your valuation.

14‘And when a man dedicates his house to be holy to the Lord, then the priest shall set a value for it, whether it is good or bad; as the priest values it, so it shall stand.

15If he who dedicated it wants to redeem his house, then he must add one-fifth of the money of your valuation to it, and it shall be his.