I have attached two pictures showing how much the concrete floor is off-level at the base of the stairs. The first picture shows the dip with respect to an 8′ 2×4 and with respect to a 4′ level. There is about a 3/8″ gap under the 2×4 and about a 1/8″ gap under the 4′ level. The second picture shows a wider view to see how the 2×4 is positioned in the hallway. The bannister at the point where the floor is dipping 3/8″ is about 1/4″ taller than on the right side, so it appears they tried to compensate for the lower portion of the floor on that side.
I plan to build up the floor to make it a little more level. My question has to do with how much I should build it up. Based upon your experience would you build it up so so that it is essentially flat when viewed with the 4′ level or flat when viewed with the 8′ 2×4? Or would you do something else?
Thank you for the information and thanks for asking about the straightness of the board. I have checked the board and it is straight. Just to make sure I have also flipped the board onto its other narrow side and the same gap is there. So I am confident it is correct.
Based upon your information I will probably fill in about 1/4″ across that area which should be pretty easy to do.