Shed floor insulation. However having a layer of insulation beneath the floor boards will contribute towards keeping the contents of the shed toasty. Warm air rises and so naturally the walls and the roof are the first areas to consider. This video covers insulating the floor vapour barrier and plywood. Is an effective but more expensive solution for floor insulation in your shed.
Raise the shed high enough off the ground so that you can get under it about 12 inches. Part 6 of a video series about how to self build a timber framed garden room office aka tiny housewood workshop in the uk. It is designed for ease of handling. The insulation for a shed floor can be installed relatively easy.
One of the drawbacks for spray foam is that you need backing for it to adhere to the surface. Insulating a shed floor is not one of the first things that comes to mind when insulating a small building. There are several options to insulate a pre existing shed floor. There are many types of insulation that you can use to insulate a shed floor.
This can be installed usually by one person but you may want a helper or two. To insulate a shed floor you can lay a thin layer of insulation board and top it off with osb or plywood to stabilise the floor surface and protect the insulation. You can use rigid insulation between the floor joists and use strapping or blocking to hold the insulation in place.