HELP...Metal Garage Foundation Question

[Engine66]

I am planning to have a metal garage 24x31 installed for tractor and implement strorage in Vermont. My site is not level and will require one side to be built up approx 36" to be level and remain higher than grade for drainage considerations. This building is by T-N-T and basically consists of the typical carport made of 12gauge metal vertical posts welded to horizontal supports held together at the bottom by a base rail on both sides. These posts form the framework upon which the metal roofing and siding are attached. I have seen pictures of these installed on bare dirt, crushed rock, and slabs. T-N-T says I do not need a slab...just level ground.

I got an estimate for a "floating slab" 6" deep with a 12" perimeter footer and rebar 24" on center set on a level pad of both sand and a crushed rock perimeter. My concern is the longevity of this type of foundation since the built-up side could move during the seasons (freeze/thaw/rain/dry) etc. If the built op side settles, I'm thinking it could cause me big trouble with cracking, etc. I was thinking of just saving a bunch of $$$ and leveling my slope with compacted crushed rock and if there's any settling over time, I can lift the rail and re-fill as necessary. This building is tractor storage...I'm not opposed to having crushed rock as a floor base and find it can become very hard and durable. Any ideas, suggestions? I know that once a slab is poured, if it is not done right, then I'm screwed. I have a budget too and this is a concern since Uncle Sam got me good this year...(I'm thinking he's lighting a cuban cigar with a $100 bill thanks to me right now) Anyway, your help or advice would be appreciated. Lastly, can a slab be poured after the fact with one of these buildings?

Thanks...

[jml755]

I've seen many garages here in Michigan where the rear had to be built up as you indicate. You need to get the bottom footing below the frost line. In Vermont, I'd imagine its about 48", it's 42" here in MI. This would mean you need to dig deeper at the "built up" side, depending on how severe a slope you use on the backfill to ensure the footing sits on ground that won't freeze and heave. As for a "floating slab, my attached (unheated) garage was built on a trenched footing and the slab poured inside the walls. This is common here in Michigan. It probably moves, never really measured it and it hasn't cracked in 20 years. I would imagine you could do the same with your building. As for just putting it on a gravel base, I've seen lots of those around here as well. Doesn't seem to be a problem, but I haven't asked any of the owners about any freeze/thaw issues they've had either. [img]/forums/images/icons/smile.gif[/img]

[jimbrown]

It's a tractor shed go with crushed rock.

[Pat]

I vote with Jim.

If you want a nice rock floor you can put down some larger crusher run (1 1/2 inch) and then top it with "chat" (fine crushed limestone with fines included.) This stuff will pack down like concrete but spilled fluids will not make such a slip hazard as with concrete. Over time you might have to "dress" it with a top application of more chat. If the dirt under all this is fairly hard and stable and water runoff is directed away from the building then a good gravel floor will last for years and years and even adding the cost of any additional gravel over time will still be much cheaper than concrete.

Pat