What can I use to make wooden structures durable?

I need to build some things on a farm such as a roof over the firewood storage area, some simple pieces of furniture, etc.. I need to make them durable and resistant to water, humidity, sunlight…and TERMITES. Is there any combination of substances that would do the job you know about, so to help me make this elixir?
suggestions as to what I can actually produce, rather than what I
can buy are much preferred.