Sloped concrete


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Old 09-12-07, 04:52 PM
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Sloped concrete

In the tenative planning stages of planning a driveway redo. The turn around by the garage has a storm drain in the middle so the cement needs to be lower in the middle, higher on the sides. So how do I pour cement with a grade like that? Maybe 6" lower in the middle at a distance from the farthest edge of 12' or so.


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Old 09-13-07, 08:12 AM
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Originally Posted by Minger
In the tenative planning stages of planning a driveway redo. The turn around by the garage has a storm drain in the middle so the cement needs to be lower in the middle, higher on the sides. So how do I pour cement with a grade like that? Maybe 6" lower in the middle at a distance from the farthest edge of 12' or so.


Thanks
Just to give you some idea, roads typically have a cross fall of 2% (.24 feet or 2.88 inches, say 3 inches). Anything greater than that would be too much in my opinion. 6 inches on 12 feet is 4.2% = very steep. But, you want the slope to handle the runoff during times of heavy rainfall. So it's a balancing act.

There is a calculation that can be done for your particular situation (by a drainage engineer) to figure out the water flow quantity but even that has to take into account the rainfall standard that you want to protect against, which does not guarantee flooding, unless you build a Taj Mahal with ridiculous impractical slopes.
 
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Old 09-14-07, 09:44 AM
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The grade was just a rough guess by me. But my bigger question is how to get the grade. Just by trowling can I get a 2% grade?
 
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Old 09-15-07, 03:44 AM
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If you haven't poured and finished concrete before, you'll have to do a lot of reading as to forming, prep work, tools needed, processes, etc. But to answer your question in a nutshell, one man holds his end of the screed board atop the drain, while the man on the other end sweeps his around in a circle at the level of the forms. That way, the concrete slopes to the drain. By the way, I'd only build in 1/8 to 1/4 of an inch of fall per foot, so the drain would be 1.5" to 3" below the form which is 12 feet away. 6 inches would be excessive.

Pecos
 
 

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