This is the 1942nd most frequent Russian word.
ремонту
The Russian word "ремонту" means "repair" or "renovation" in the dative case.
In this sentence, "ремонту" is the dative case of the noun "ремонт", indicating that the house underwent the activity of renovation.
Дом был подвергнут ремонту.
The house underwent renovation.
Here, "ремонту" is again the dative case of "ремонт", used to express the concept of being 'subject to repair' within a negative context.
Эта комната не подлежит ремонту.
This room is not subject to repair.
In this example, "ремонту" takes the dative case to indicate the purpose or object of the preparation—renovation in this case.