Toledo Talk

Att. Engineers -Maximum Driveway Approach Slope ?

I need some information. The street where I live has been torn out for a complete replacement. The level of the street dropped appriximately 3ft. I will use a laser level tonight to determine the exact drop from the edge of our existing concrete driveway to the new curb cut. What I need to know, hopefully before they dig and pour the new approach, is the maximum allowed slope. Where they have the driveway currently cut back to, there is stone between the curb and the current driveway edge. Both our cars scrape the ground trying to get up the driveway because of the steep slope. Plus there has to be a flat spot for a 4'sidewalk. I don't see how they can get it all in.

created by holland on Oct 06, 2008 at 05:08:23 pm     Comments: 10

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Rather simple calculations. What is the wheel base lengths and the ground clearances of the vehicles you have. What will be the horizontal length(sidewalk to curb)of the new approach? What will be the vertical rise (street to sidewalk)of the new approach? You'll need all of this first. Or of course you could just get a Jeep or Hummer.

posted by AmericanPie on Oct 06, 2008 at 07:07:47 pm     #  

The rise to the existing concrete drive is 13" We have a Miata and a Ford conversion van. What I need to know is the amount of run I can expect to comfortable navigate the rise. I understand the equation of rise divided by run to get the slope. But what is the maximum allowable slope. I mean, what if the next person who owns this house has a different vehicle? Aren't there standards?

posted by holland on Oct 06, 2008 at 07:13:03 pm     #  

I should add that the driveway has been cut and if the approach is poured to the cut the slope will be 12.5% (96" run 13" rise). Both our cars undercarriages scrape the temporary stone approach currently in place. In the winter I'd have to back across the street into the neighbors driveway, gun it and go full bore to get up to the driveway and hope I can stop before I hit the garage!

posted by holland on Oct 06, 2008 at 07:17:45 pm     #  

The present slope you have given is little over an 8 to 1 (8 ft of run to 1 ft of rise).
What you are looking for is min. slope of 12 to 1 (12 ft of run to 1 ft of run). This should work fine. This slope is use by our office all the time and I use it a min. slope , but I always try for a 15 to 1 when I'm checking driveway slopes in the field on my projects. (15 ft run to 1 rise)slope. There is no maximum slope for a drive. The slope could be as gradual as a 20 to 1.

posted by whitehouse on Oct 06, 2008 at 07:54:37 pm     #  

Something isn't right here. It's only a 7.7 degree angle. If your Van has a 100" wheelbase the clearance needs to be only about 3-3/8". If the wheelbase is 120" the clearance needs to be about 4". If the wheelbase is 130" the clearance needs to be about 4-3/8" This of course assumes that the driveway surface is approximately parallel to the roadway surface. I would think most any Van should be able to navagate this, I don't know about small sports cars.

posted by AmericanPie on Oct 06, 2008 at 07:59:37 pm     #  

Do you live on Merrimac?

posted by transcom on Oct 06, 2008 at 08:44:21 pm     #  

That's what I needed to know Whitehouse. The project engineer is coming tomorrow to look at the approach. I forgot that somehow a 4' sidewalk has to get in there too. Do I add 4' to the run plus the 12 to 1 ratio?

Nope, I don't live on Merrimac. And the van's undercarriage does scrape the temporary stone approach. The Miata almost perches. We actually are parking the Miata at a neighbor's until we get this resolved. It's possible we measured the run incorrectly. The rise we measured with a laser level.

posted by holland on Oct 06, 2008 at 10:32:35 pm     #  

I was just curious...Merrimac was totally ripped-up back in august and they are still not done with it. But I thought it seemed lower as well. I just wish it would get done cause it's blocking my way to Central.

posted by transcom on Oct 07, 2008 at 08:28:31 am     #  

transcom I'm sorry to hear that you're going through what we are going through. They started here Aug 1st. We have to park on a side street and hike in with groceries etc. For a while we had a 2' ditch between our house and the road. So you had to jump and climb! The ashpalt plants usually close the first week of November. These guys gotta shake a leg.

posted by holland on Oct 07, 2008 at 11:32:47 am     #  

We got our plan today for the driveway approach. The slope will be 9.28%. I was able to speak intelligently to the engineer. Thanks All - in particular to Whitehouse.

posted by holland on Oct 08, 2008 at 02:20:59 pm     #