I'm making an adirondack chair using oak and cedar pieces all reclaimed from pallets. I've decided to stain the project instead of painting. I've chosen stain partly because I can't afford to buy any primer and paint right now, but also I thought the stain would hold better in the dryer heat of summer where I live in southern Oregon....
My question: is it better to stain the pieces individually before putting the chair together, or can I put it together and then stain? I already assume that I have to poly it after constructing the chair just curious regarding staining
Unless it is an outdoor stain, it will not provide any protection from water and UV rays and so the decision to apply stain before or after assembly does not really matter in that regard. However, if you're using an outdoor finish then the application to the parts before assembly will help to seal the wood and prevent the wood surfaces from absorbing moisture.
Wood finishes break down with exposure to sunlight. As the finish breaks down the wood will begin to discolor and crack from exposure to rain water and UV light.
The outdoor finish that lasts the longest and provides the greatest protection against the elements is paint. There are some very good outdoor paints available today which will last many years with nothing more than cleaning and an occasional bit of touch-up. I understand that the paint is beyond your budget for this project but you may find that the stain and poly approach the cost of paint. And if you don't mind a painted finish then you'll find that paint will be less expensive in the long run because it will not require refinishing so often.
If you plan on using polyurethane varnish then I suggest that you use a spar varnish. Wood used outdoors will expand and contract more than wood indoors because of the greater fluctuations in humidity. Spar varnishes are designed to have greater flexibility to prevent cracking or crazing under outdoor conditions. Also, some spar varnishes offer UV protection.