My parents own a camp in the woods located 20 minutes from town. The summer time is used to do repairs.
The joists under the camp have rotted a bit. One of the supports for the deck on the side has collapsed. The camp does not have a cement foundation and is built on the ground. In attempts to keep the wildlife from getting under the camp and keep the cold out in the winter it was closed up. After 20 years of having no air flow, the joists have some rot, causing the floor inside to be springy.
The solution is to take all the boards off one side of the camp. Get someone small to crawl under the camp. One joist at a time, jack the camp up at each end of the joist just enough to slide a new joist in place then set it back down. This time a few openings with wire mesh will be used to allow some air to flow under the camp. These will be closed off in the winter to keep the cold out.
The forest provided much of the lumber needed to build the camp and the wood used to heat it in the winter.