Is floating slab good enough?

[DanIndiana]

I have a hard time logically understanding why a floating slab is ok for a garage and not a house. I like the idea of saving money, but I want a building that will hopefully still be here for the next generation. We're doing a 26 x 40 garage (1040 sq ft.) in NW Indiana. Frost line is 36". Local code says everything over 750 sq ft. needs a foundation to the frost line, but building inspector says he will pass a floating slab if it's 20" wide at the edge instead of normal 16"; with wire mesh in it also. What is the rationale for why it's ok for a garage slab to float but not a house? Will the building last? It sounds less than ideal.

Thanks,
Any help would be greatly appreciated.

 

[RVDan]

A garage on a floating slab will move with the ground, no big deal with a garage with no utilities. Do you want your house to move independently of the sewer lines, water supply, and gas lines?

It's good enough for a garage because if the garage blows over in a storm or floats downstream during a flood, who cares? If the house floats away while you and your family are sleeping in it, it could be life threatening.

 

[DanIndiana]

Thanks for the response. I hear what you're saying, but what if the garage does have electric lines, gas line for a heater, etc. Is a floating slab not allowed when certain utilities are involved? I realize your children aren't sleeping in it at night, but it's still your investment. I believe you are right though, that the basis of the argument is 'it's a garage, who cares'. There's got to be a bit more behind it, right?

 

[brownbagg]

why not ask the building inspector, we have flowing slab here for houses but our freeze line is plus five inches

 

[kbs2244]

There are lots of houses built on slabs.
Up north it fell out of favor in the 1950’s
But it is still common in non-freezing parts of the South.

The biggest problem is running water and heating pipes and ducts.
With a basement or crawl space you just go down there and fix it.
With a slab you have to tear up concrete.

But all your commercial and industrial building are on slabs.
Thick ones to take heavy loads.
The heat is usually overhead and the plumbing is kept to a small area where it is buried in pea gravel that is covered with a thinner concrete floor for ease of busting it out if needed.

 

[MScott]

Built my first garage back in the 70's on a slab. (28x38) It is still standing and, other than initial shrinkage cracks, still solid. I'm in the process of building another the same size, but since this one is attached I used a foundation. I used steel mesh in the concrete in both. I'm not sure if a floating slab is even allowed here now but I didn't check..

 

[p_mori7]

Electrical is not a problem. Just don't run the power cable through the slab. Rather, run it up the outside wall and through an LB.

See post #82 of my build thread.

 

[OccupantRJ]

My previous shop was concrete block on a monolithic slab. It survived several days of 5 feet of flood waters with a 10 mph current. Hosed it out and kept getting up. Shop is still in great shape.

 

[BFalfa]

pole barn type buildings are basically just a a slab aren't they?

 

[OldmanB]

My shop is 23 years old built on a floating slab,with water and power lines coming up from the floor and never had a problem with movement. We had over 4' of frost in the ground this year.

 

[Daniel Dudley]

pole barn type buildings are basically just a a slab aren't they?

No, the poles are set deep in the ground on footers or in concrete plugs.

 

[Daniel Dudley]

I'm a big fan of high drainage gravel under a floating slab, and rebar at least around the perimeter.