Learn about the Durability of Wood by reading this series of pages from the Canadian Wood Council.
  From the University of Minnesota, review Deterioration in Historic and Archaeological Wood.  Examples of remaining wood timbers at Chaco Canyon are of particular interest.
  An excellent article on Pagodas in Japan.
  In current-day construction, the problem of ever increasing member size with increased span was solved by creating larger, longer members using smaller boards and gluing them together.  Example of these glued-laminated beams or glulams are shown in this photo.
  Here we are in the long-ago time.  Simple buildings constructed with either wood, stone or unfired clay walls (depending on your locale) and a wood roof.  As the model at left shows, a primitive dwelling can be quite small if the available roof members are not very long.  What if all you have are the branches of local trees?

  At the opposite extreme, long roof members have their limits too.  They must be very large to span between walls and an organized crew of workers or special machinery may be required not only to transport the member from where it was milled to the site, but also to lift it into place on top of the walls.  A significant commitment of time and labor is necessary.

  Wood structures were popular wherever there was a supply of timber, but wood as a construction material has its drawbacks: (1) wood will burn; and (2) wood is subject to attack by insects and other organisms.  These are issues engineers still deal with today.