Leviticus 27:13-15

13But if he would redeem it, then he is to add a fifth to its valuation.

14“If a man consecrates his house as holy to Adonai, then the kohen is to evaluate it, whether it is good or bad. As the kohen evaluates it, so it will stand.

15If the one who dedicates it would redeem his own house, then he is to add a fifth of the money of your valuation to it, and it will become his.