I search for solutions in this order: Past Code, Unreal Source, Wiki, BUF, groups.yahoo, google, screaming at monitor. – RegularX
From Unreal Wiki, The Unreal Engine Documentation Site
This creates a curved stair for the red builder brush
- Inner radius - this is the radius from the centre of the brush (the lone red point) to the staircase itself. This value must be larger than zero.
- Stepheight - The height of each step. don't know the maximum height with walking, but when it's 32 you must jump
- Stepwidth - The width of the steps
- Angle of curve - The rotation of the staircase. Must be between 1 and 360
- Num of Steps - The number of steps
- Add to first step - the extra height the staircase gets. handy if you want a staircase that starts a bit higher
- Group Name - Doesn't do anything with it
- CounterClockwise - switches the lower and higher part. With C it goes up to the right, and with CC to the left
 Aligning Tips
Use different textures. Use a texture for the walk surface of the stairs, and another one for the rest. Use align wall direction at the sides to make it look nicer and you don't see those ugly lines.
This is i think the best way for the curved staircases. The linear can have the same.