Can anyone tell me the formula for calculating the length of an "S" shaped length of wall?
If the "S" is composed of two simple curves with the radii known, then it is very simple:
Radius * ArcInRadians
What information do you have about the wall.
Most architectural "S" walls I have seen are designed using spirals. So a bunch of little technical details are needed to calculate the "length".
Is the "length" defined as the reference point on the front face, or some point in the middle of a cross section, and is the wall completely symetrical about the inflection point?
Do you have more data?