7,200 sq ft RV storage on shallow foundation

[TroyD]

S. Minnesota. 42" frost depth. I have a client who has built many large self-storage garages and RV/boat storage buildings on floating slabs with thickened perimeter grade beams. This is a rural location where the building code is not thoroughly enforced. He would like to build a 60' wide x 120' long x 16' tall RV storage. Stick-built or glulam posts with column brackets anchored to grade beam, engineered roof trusses. Lots of interior divide walls anchored to thickened interior slabs. While the IBC restricts these buildings to 600 sq ft, the local building official will allow it with and engineer's stamp on the shallow foundation. There is no soils investigation, but the USDA Dept of Ag web soil survey data from this location is shown below. Without getting a geotech engineer involved, is it reasonable to just remove the silt/loam material and replace with sand?

 

[dik]

excavate for a depth of 4'? The high range of the 200 sieve is frost heave susceptable and can be problematic... 4" rigid polyurethane foam under might help with it extending 4' beyond the building footprint and use geothermal heat. A 12" wide x 16" deep perimeter stiffener with a 5" slab would likely do the trick, but it's a little iffy... and you want the client to take the risk. Sawcut into 15' or 20' strips both ways. Unless you have actual bearing walls on the interior, I'd try to avoid slab stiffeners, else you have to sawcut on each side of the stiffener at the slab edge. Stiffeners restrain concrete shrinkage and will likely generate a crack unless sawcut on each side of the stiffener. Sawcut at the right time...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik