Add special constraint to avoid duplicate rows with this condition?

You can create a filtered unique index with a WHERE clause.

CREATE UNIQUE NONCLUSTERED INDEX IX_[index name]_FloorNum_BedNum ON [myTable] (
    FloorNum ASC,
    BedNum ASC)
WHERE (IsActive = 1)

This will only take into account records where the IsActive column is set to 1.

Based on your description I think that ClientId is not necessary in this example but if I am wrong you can add it to the index as well.