We built our current house 20 years ago, close enough. The ensuite sink was leaking somewhere and dripping onto the floor. It is a bowl set into a thick plank of jarrah with a small return on the front. Expected it to be the piping underneath as I just cleaned that out (lovely job, highly recommended). Nope not there. Ah, the silicon seal between the timber benchtop and the set in bowl thingy has split. Easy fix, dry off the top and then redo the silicon. Look underneath and find some folded cardboard that was put there by the cabinet maker to stop silicon oozing through. 20 years it has been there. Stuffed now though because that was where it was leaking and the cardboard is very very wet. Amazing.