Dado Rail Height ??

[comfortably_numb]

Ok that puts my mind at rest ... There is no picture rail & no dado in any other room so gonna go with 40" then, if decided to do lounge at later date can follow on

[Hoovie]

you can add a picture rail in the hall and paint above the rail the ceiling colour to reduce the height

Would that work in a Hallway (assuming the hallway also includes stairs along a wall which is the most common)

If you extended the picture rail up the stairs, then there would be a coming together of picture rails with ceiling colour on walls above and below rail.

Or you stop the picture rail at the start of the stairs and go vertical, which would give a side-by-side colour change

I do the ceiling colour above rails upstairs in bedrooms actually and I think it looks good and it is effective - but can't visualize it in a HSL.

[big-all]

you can add a picture rail in the hall and paint above the rail the ceiling colour to reduce the height

Would that work in a Hallway (assuming the hallway also includes stairs along a wall which is the most common)

If you extended the picture rail up the stairs, then there would be a coming together of picture rails with ceiling colour on walls above and below rail.

Or you stop the picture rail at the start of the stairs and go vertical, which would give a side-by-side colour change

I do the ceiling colour above rails upstairs in bedrooms actually and I think it looks good and it is effective - but can't visualize it in a HSL.

several ways of doing it

if your picture rail terminates you continue the coulour underneath to the ceiling in a strait line at right angles at the end off the picture rail

if the picture rails are close but at different heights the a straight line between them as long as it looks right