Currently building an insulated shed, laying asphalt board now and wondering if we need to seal the gaps between the asphalt board and the decking we nailed under the joists. In some places, there is a gap straight down to the ground where we haven't placed decking.
I assume you mean that the asfaboard is the subfloor. I also assume that the friggebod is on a simple foundation, like plinths. The problem then is that the wind can blow into the insulation and the mice get an open highway into the floor - so yes, it should be sealed, preferably with battens so that the board doesn't start sagging over time.