Question: I’m finishing a basement in an 80 year old house. I need to add a 30 foot partition wall to contain the mechanical area (oil tank, furnace, breaker panel etc.) and add a bathroom. I notice that the floors dip considerably toward the center of the home. If I use the floor to measure from, won’t all the doors along this wall be at different heights once they’re installed? What’s the best plan here?
Answer: GREAT question!
Basement Remodeling: Keeping Doors Level
The first consideration in basement finishing is to ensure it’ll stay dry. Assuming that, let’s get back to the question.
The short answer is this: for the room to look right when you’re done, all the door heads (or tops) should be level with each other–regardless of what the floor is doing. I’ve seen floors pitch and undulate like crazy so using the slab as a control point for layout is a big mistake.
The solution I usually use is this: Since flooring (tile, carpet, etc.) can usually be built-up more easily than doors cut down, I usually use the highest portion of the floor as my control point for layout. I then install the doors so their head-jambs are level from that point.
To determine level, I use a laser level to establish a reference point.
There are cases where it might be easier to blend the two approaches: cut a door bottom on one end of the room; shim the jamb-legs up a little on the other.
I wish I could be more specific but there are a bazillion possible iterations. Bottom line: keep the door heads level and pack up the floor to meet the bottoms of the jamb legs and you should have a room with trim so even it looks like it grew there.