max. Driveway Slope 5

[wslainc]

I have a Driveway and garage relationship of 46' in angle length and a 9'6" difference in vertical ht. I calculate that this driveway is at about 21-22%. Is this acceptable in California Specifically the Hollywood hills. I am the Architect and the contractor has graded this and they are ready to pour. The big problem is there is no more horizontal length for us to reduce the slope.It seems visually that many hillside homes have driveways at even steeper grades, but this one is my project and I am wondering if this is an acceptable single family residential condition?
Thank you.

 

[digger242j]

I'm certainly not qualified to speak about what's allowable in California, but I can tell you that I've worked in certain jurisdictions where the driveway slope was subject to local regulations. Something like the first five feet behind the curb was not allowed to exceed a certain percentage, and the next ten feet not allowed to exceed some certain *greater* percentage, and beyond that was not regulated. I'd be lying if I said I had a specific recollection of what those given percentages were, but I'm pretty certain they were less than 21%. This would, of course, make the remainder of your driveway beyond the first fifteen feet steeper still.

 

[TerryScan]

You would really need to contact local code enforcement. A quick web search revealed maximum grades between 10% and 20% in various California municipalities.

 

[Maury]

20% seems too steep, but I live in northern Illinois. This may be acceptable in southern California. Don't forget to consider the grade transitions to the garage floor and to the street. Extremme grade changes in short distances will cause vehicles to bottom out, usually at the rear bumber but sometimes in the middle. Architectural Graphic Standards has vehicle dimensions and clearance angles.

 

[swBausch]

With that amount of difference, why not a basement garage?

If not a basement, you could reduce the slope by some excavation and some retaining walls. The difference would need to be made up with a staircase or terraced walk, but those can be design elements.


Just wondering, was it the floorplan/zoning/architect/owner that ruled out the alternatives to a steep driveway?

 

[swBausch]

Here is some additional information:

http://www.ci.manhattan-beach.ca.us/commdev/handouts/building/driveslope.htm

http://www.rurdev.usda.gov/ga/slope.htm

 

[RCEJD]

I have been engineer in this area for over 15 years. The first question you have to access: Does the Fire Department require assess to the house (hose pull distances). If so, you need to fullfill the County Fire Requirements. Otherwise, you are only going to me mandated by the local agency (City of LA) requirements.

Generally you are going to consider cure radius and grade beak situations, i.e. preventing the cars from bottoming out. It is not unusal in LA/Malibu/Hollywood Hills for driveways at 20 percent.

Good Luck.

 

[swine]

LA County Fire Department requirement is 25% max, with some other restrictions and requirements placed thereon. I highly recommend against anything above 15%. Particularly since you have no experience, you may still mess it up. Your client won't like when their limo bottoms out, or there Mercedes muffler scrapes on their way into the garage. Not to mention the very uncomfortable feeling of such heavy slopes.

You certainly need an engineer with some roadway/driveway layout experience. This is the type of thing that is so difficult yet so under-appreciated. Find a good civil engineer.

 

[swine]

Oh, forgot, does anyone know of some nice vehicle templates (for free) on the web?

 

[hawstom]

Do you mean turning templates? I put some up at my site along with a turning path AutoLISP program a few years ago. It may help you out.

http://www.hawsedc.com/gnu

Tom Haws

 

[ALBUD1962]

I know this might be a little late, but driveways steeper than 12% should be avoided. 15% is the absolute maximum.