I don't see the floor lasting 20 more years with that plan. If you are able to lift the building to alow air circulation between earth and floor,that will extend life of floor. If the size restriction is the only reason you arn't replacing the shed,"remodel it". Chances are you can all but build a new shed as long as you preserve some of the origional structure. Get a copy of the ordinance and read it to see if it forbids preserving non-complaince structures. Douptful since that would mean they would be an eyesore on the way to becoming unservicable. The ordinance likly says the structure must be kept in good repair which would be your permission to do the remodel.

You have to get air under the floor AND stop the transfer of cold through it. Metal flooring is an excellent heat/cold transfer medium. I would get rid of the metal floor and use wood only with air vents along the outer edges of the shed. You would also want to cover the ground with a sheet of plastic to stop water vapor. That plastic will have to be attached to the walls so no gaps are present. Study up on how they do craw spaces and you will know what you need to do. That may mean that you'll have to raise the floor or the shed a tad for air vents. (keep the critters out!!) Spay insulation is better than sheet as it doesn't leave an air gap.

Maybe cut out the metal flooring and fill it in with cement?

... oops
Good luck with what you did or are still planning

Mark

This post was edited by AnEv942 on Fri, Nov 15, 13 at 19:41