You might call it dumb luck, but we like to refer to it as careful planning.
The stairs are on the south edge of the room, and the factory-manufactured stair nosing had a groove in it. So the floor had to be installed starting at the north edge of the room, because you nail into the tongues of the flooring. But how, pray tell, do you make sure that the flooring meets up with the stair nosing in the right place? If it was off, we would have to rip down an entire course of floor the length of the entire room.
So we measured. And measured. And did some math. And measured and did math again. We laid out a few boards and figured that each joint added 1/32" to the boards themselves, which are 3.75". So we multiplied 3.78125 by the number of courses of floor (it wasn't actually that simple), and then snapped a chalk line where the first course should be nailed. And then we hoped for the best.
This is the line that we have to meet up with, see it a few inches from the edge of the stairs?
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It is where the factory stair nosing ends.
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So we got 3 courses away from the stairs, and stuck in some scraps, and it is going to be
perfect. ...to the 32nd of an inch....perfect.
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and that, my friends, is what happens when an engineer builds his own house.