Maximum common drive slope considering "icy" conditions ?
Maximum common drive slope considering "icy" conditions ?
(OP)
Does anyone have information on the maximum slope a common drive can be? I am located in north Georgia where snow and ice can be a concern from time to time. There are existing drives that exceed 20% in the area; I just don't know how passable they are in icy conditions.
The current regualtions for a subdivision streets set the maximum slope to 14%; since "common drives" are private the maximum street slope does not apply. Interestingly the 14% street grade appears to conflict with the International Fire Code max of 10%
Any help is greatly appreciated
Thank you.





RE: Maximum common drive slope considering "icy" conditions ?
Regardless, I would shudder to think about a 20% driveway with ice on it, unless I had chains on all four for traction and braking. Given my choice, I'd avoid anything steeper than 10%. Fourteen is too steep, IMO.
I should note, however, that gravel is usually better than pavement in this regard.
RE: Maximum common drive slope considering "icy" conditions ?
RE: Maximum common drive slope considering "icy" conditions ?
Where is the sun with respect to this? Sun shining on an asphalt pavement does wonders. Even without the sun on a cloudy day day, that black pavement is warmer than concrete.
RE: Maximum common drive slope considering "icy" conditions ?
1. Hold design to 10% max.
2. If you need to go steeper than 10%, having pavement and south facing is most desireable. Anything you can do to increase sun exposure is a plus (including removing vegetation).
3. If you have to go steeper, but do not have good sun exposure, try to keep the steeper portion of the driveway away from the driveway/road intersection, to give vehicles coming down the driveway an area to stop, before sliding through the road and potentially hitting another vehicle. For example, I would rather design a road with a 30'-40' flat area (<5%) at the road intersection, and then 14% for 200' up to the house, than having a 250' driveway with a straight slope from house to road at 12.5%.
4. If you lack sun exposure, gravel is actually better than asphalt (doesn't ice up as easy).
5. Finally, if it's economically feasible, you can heat the driveway.
Also, be very careful with liability!!! If you design a driveway, and emergency vehicles are unable to access the house due to an improper design on your part (i.e. too steep, insufficient cl radii, etc.), you could be held liable. So IF you go over a 10% design, limit your liability before you sign/stamp.
RE: Maximum common drive slope considering "icy" conditions ?
Our code stated maximum was 8% for drives and 6% for roadways. One of the local fire protection districts ran live tests using their equipment on one of the older roads in the county to help us develop the code. Emergency access drove the requirements.
I agree that 10% is likely the upper boundary. Any steeper and it gets really problematic for most vehicles.
civilman72 gives some good ideas to consider.