Direction of hardwood floor?

Run it the longest way in the room.

What does "diagonal" mean?

Diagonal means to run from corner to opposite corner. It seems the trendy way to do it at the moment, but I have always done it as the Tudors, Stuarts, Georgians, Victorians and Edwardians have done it. Parallel with the longest wall if at all possible,
However, if the joists run that way, then obviously it would be necessary to fit the boards across them (90 degrees to joists) accordingly.

The best direction of the finish floor can depend on the underlying structure.

If the structure of the house includes sufficient stability then square with the house would be OK either way.

But if the house does not have much holding it square then putting the finish floor on the diagonal would make it better. This would put a bunch of triangles in to help hold the house square.

If you have a plywood sub floor then it would only be asthetic. If no sub floor it would be important.

I know what diagonal means, but have never seen that placement for hardwood flooring.

I'll look it up.

Later . . . Oh - I see. I don't like it. Makes me dizzy.