any ideas on foundation renovation

[bizrepair]

hello, i have this lovely little 16X20 shed i built a few years back. the foundation is just patio stones. i built this building just for storage but now i would like it to be a year round insulated heated building for a music room for myself.
i would like to raise up the building and slide  foundation beams under it. i was thinking this might be possible. or should i let it sit where it is.
It hasnt moved alot and as you can see it aint too straight thats another story. im thinking of making the double door opening a glass wall and insulating the floors with styrofoam and plywood. the roof is only 2x4 so what would be the best way to insulate the ceiling???

[glenn kangiser]

I would think that roll or batts would work - I assume you want to keep it light because of the 2x4 's - Trusses? Acoustic tile  suspended ceiling is fairly light too.

[John Raabe]

You could raise the walls and put in a proper foundation under it (concrete or PT wood). That would be the long term best investment in a square and level building you would be willing to buy things like french doors for. If the 2x4 rafters are sufficiently braced for your loads you could use R-13 batts and an inch or two of foam on the bottom.

The floor I'm not as clear on. Is it a poured slab now?

[desdawg]

I would think you could carefully jack it up and slide a pair of 4X6 skids under it, then frame a 2X6 floor on top of those skids. That would reduce your ceiling height by 6" or so. The skids should be redwood or treated lumber. You would then have a "portable" building not subject to property taxes. Adding a perimeter foundation would put you back on the tax roles.