The usual problem run into when building under codes and wanting to use your own lumber is that it is not graded. If that is the case in OR it will be the structural that would need grading; lumber for siding, inside or out, does not, except for appearance grading. If you be hiring a sawyer to turn the
trees into usable timber, planks or boards look for one that is able to grade and certify. If that is not possible some folks have had success in selling their timber to the sawmill/sawyer and using the proceeds to buy commercial lumber.
For non conventional structures you may need engineering to obtain a permit. You'll have to check what they will and will not do.
You can view the 2008 Oregon Residential Code
online at
http://www2.iccsafe.org/states/oregon/08_Residential/08Res_Frameset.html It's view only, no printing. You might be able to get it all to download if you use Firefox and have the DownThemAll plugin. It has worked for me before.
OR has lots of info online.
http://www.oregon-epermitting.info/ http://www.cbs.state.or.us/bcd/programs.html http://www.cbs.state.or.us/bcd/programs/online_codes.html I can't say if there are areas that are not as diligent in following the "book". I know of a few people who have built in OR and they all had pretty stringent requirements as I recall. Maybe someone will drop by with specific county info. I know OR has a pretty strict policy on
wood stove installations in new and remodel construction. Best of luck!