Replies

1. 
   FastEddie1 | May 23, 2003 05:04am | #1

   You might ask an geo-engineer for help with the foundation so you don't have problems with it washing out.  The slab and foundation by themselves (itself?) is no biggie, it's the soil that you need to worry about in this case.

   Do it right, or do it twice.

2. 
   booch | May 23, 2003 05:46am | #2

   Would you pour concrete walls, fill in with "gravel" and install lots of rebar or metal "screen"?  Would you excavate to a common elevation and then pour footers, block, fill, rebar, and then concrete?

   No, the slab must float as a unit. You'd have to scrape down to mineral soil fill with fill/gravel to grade then float your slab.

   You need to make a footing if you put the wall down first. The depth of the footing depends on the soil and the climate (below frost line)

   I'd phone the inspector if you know him well or the soils engineer. 2 story garage? Must be tough getting the car down the stairs in the morning.

   Jack of all trades and master of none - you got a problem with that?
1. 
   Ethos | May 23, 2003 04:39pm | #3

   Sounds like you are really bidding a combination garage/ erosion control structure.  Minimize the erosion control aspect and the first time the wash flashes post-constuction your phone's gonna be tinkling.

   I'd design and bid an erosion control structure first.  If the owners accept this approach- and the associated costs- then I'd design and bid the garage structure in such a way that it is founded on the erosion control wall.

   Try and get out there during a heavy and prolonged rain after the upper watershed is saturated.  Otherwise it's hydrological analysis to figure what the flows in that wash can be and so how much scour the wall is going to have to resist.

   I'd bet that if the owners are recent on the site (and have never seen the wash flash) that they won't go for it.  That's your indication to run the other way.  There are also probably setback issues to be addressed if someone's going to pull a permit.

   Lance

1. 
   BossHog | May 23, 2003 05:28pm | #4

   Good point - Checking the situation out after a rain.

   It might also be a good idea to go there WHILE it's raining to see where the water is coming from, where it's going, and how fast. Action may not always bring happiness, but there is no happiness without action. [Benjamin Disraeli]

1. 
   DaveRicheson | May 23, 2003 06:15pm | #5

   I agree with the others about the errosion control issue.

    The footing can be stepped down to achive the correct depth for frost. In a stepped footing I place the steps a minnimum of the frost depth back from the grade transition point, and if using a block frost wall it should be in increments of the block size. For a 30 inch frost depth the step would be 32 inches down (4 x 8" block hight) and 32" back (2 x 16" block length) from the point that the lower footing achieves the 30" frost depth. Step it back up the same way when you reach  a point that the grade transitions back to the original level. After the footing and frost wall are complete fill with sand or DGA inside the wall, being sure to hold it down below the top course of block enough to place the slab, or even with the top course and pour the slab as a cap over the frost wall. When using a block frost wall I like to slush the web of the block full of concrete. I also stub vertical rebar out of the footing at 2' o.c. and use a horizontal reinforcement like DuraWall every 16 inch.

   If the soil is not expansive there is no reason to float the whole structure. I do like to float the slab inside of a block fondation by using expansion joint material around the perimeter to isolating the slab from the foundation or frost wall.

   Dave