How "harmful" is an unleveled, sloping floor with regards to installing parquet? (Strictly about renovation works, ignoring concerns about the owners, myself, feeling the house is sloped) Background: We've stayed in the house for a couple of months and the tilting didn't bother us, though visitors who come will sense it. The parquet floor wasn't done well (previous post months ago) and we decided to have the contractor rip up the floor and do-over. The slope is quite significant: 165mm from one corner to another corner (14m).. this also mean to level everything will add that much cement -- is it even allowed to add so much cement? Hence I'm wondering how much sloping can the house "put up with" before it affects the parquet (reason why we rip up the place). Or is this totally unavoidable, a 100% level floor is the best thing to do, everything else is necessary collateral damage