The Society of American Archivists has a very
nice basic manual series that includes architectural
drawings.  Blue prints and diazos are especially
sensitive to light, and do get frail fairly
early in their lives.  I have not tracked this
thread back to see where (geographically) it
came from, but several years ago I participated
in a conservation survey (IMS funded) on a
collection that included lots of architectural
prints and drawings, and got good advice from
LofC, Office of the Architect of the Capitol,
and National Archives on which conservators
specialized in architectural documents.  The
conservator who did the survey was great, and
the whole process was very positive.  Does
anyone know if the IMS conservation survey
grants survived the budget cuts?