Dealing with a sloping grade garage slab

[Jayhem]

Ok, last question about this.

Here is where I'm at on the layout. My natural grade on a 26' Wide garage design is 18" lower on the left side of the slab as it is on the right.

In order to place my slab surface 6" above the grade on the right that puts it 24" above the grade on the left. This means I'll have to use up to 12" of fill on the right side of the pad before laying my gravel and concrete.

This also means I'll have to build up a ramp 24" high on the left side of the driveway to get into the garage. Is this an issue.

Am I better off cutting down the grade on the left side of the pad site and installing a short retaining wall or swale and french drain? I don't like the idea of placing a concrete floor over recent fill, even if it is compacted properly.

Thanks.

 

[tjdux]

Thats seems like pretty standard dirt work for building a building. I am aginst cutting down the hill and going below grade and using retaining walls or french drain becuas that just makes it too easy for water to sit near/under foundation that could cause premature concrete failure.

If you're going to cut down the high side go far enough out that the you create downhill slope at leat 10 to 15ft away from the building.

A good dirt worker should be able to compact fill dirt and have no problems. Possibly cut some off the high side and use ot to fill the low side.

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[Falcon67]

I think your choice is cost of fill vs cost of removal (that's a hella lot of dirt) and water management engineering from burying the high side wall down in the dirt.

 

[Captain Spaulding]

If you remove dirt to build, you open yourself to water issues. Building it up is easy. Stone with fines will make a nearly solid surface and can easily be laid down 2ft thick without compaction.

 

[LXCam]

Cut it and do a retaining wall to divert water flow. In-fill and compaction costs let alone what you'll need to do for an approach will be greatly offset.

 

[ssdave]

I just filled my 36x48 with about a foot of pit run rock fill. I did the work myself so that I had control over the compaction, and did it in 6 inch lifts. It cost me just over $500 for the fill material, delivered. $235 for the equipment rental. A day and a half of labor. A lot of the cost of the fill material in your case would be offset by the savings in not having to dig out and dispose of earth, plus the extra screwing around with drainage and regrading to drain, etc.

I'd fill every time before I would cut unless the fill screws up the grade of the rest of your site. Proper compaction is not difficult, nor expensive. It just takes a commitment to do it right.

 

[Jayhem]

FILL IT IS!

I live next to my inlaw's 230 acre farm. Getting fill dirt for free isn't an issue. We have a crushed shale pit on the farm we can use that, apparently it's good for road base so should work better than clay subsoil fill.

Since my house is on the right side of the garage, just under 11 feet away and we might decide to do a breezeway connect to the garage, a french drain is not going to work.

Thanks!