Snooze, 24" wide. This is 6" more than the board. Glad to hear it is working for you and I will definitely keep your sizes in mind if I don't find the 18" large enough.
I have a very large (60" x 96") padded and raised table which I formerly used to make draperies, bedspreads (custom sewing for the home of others), but it is in the basement and I am not doing stairs like I used to. It is great however, to stretch out a quilt for sandwiching. My friends call and reserve time on this table just to keep us off the floor. -- Guess this is why I am so interested in a larger surface on an ironing board.