The last company I worked for had a 14 and a 16 foot wooden ladder and a local theater has a 16 foot a frame with a 10 foot verticle extention all made of wood. They were all custom builds. A local jail has a 3 tier wood extension ladder too and I have a great stoy to tell about using that puppy but not in print ;-)
From a construction perspective I can't see how it matters as long as there are no live wire involved.
