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View Full Version : How steep is too steep for a driveway?



slantedhorse
Jul. 20, 2010, 09:43 AM
Looking to put some gravel down so we can more easily reach the back of our property. It's hard to figure out where the driveway should go. The excavator says 12% grade is about the max. for a standard drive and it seems to be right at that number (using 100 ft tape and the level... it drops 12ft).

What if you had a 4 horse trailer loaded and were headed down? Would that feel uncomfortable? Would you have to have 4WD to come up?

I've practiced it with my 3 horse but it wasn't loaded and there's no gravel on it.

csuebele
Jul. 20, 2010, 10:14 AM
Hard to say without really seeing the conditions. I don't think going down would be a problem. A 4WD would, of course be ideal, but a 2WD might be okay. On the steep part of the drive, I would use rough gravel say at least 3/4" rather than a pea-gravel for better traction. If using a 2WD, most likely, you want to be sure you don't have to stop on the steep part especially with a loaded trailer. You want to go fast enough to keep you momentum going, but not so fast you jostle the horses. We've got just a small area going up to our barn that trucks have problems with, and I make sure I never stop there. Of course, it's between two tight gates, so you really have to get the hang of backing out of the area just right.

ReSomething
Jul. 20, 2010, 11:59 AM
SOP where I grew up was to put in switchbacks for extremely steep roads. Road building was a very formal process and a big PITA as the mandate was to avoid erosion and protect stream habitat.

Around here people try to go straight up and then run the road along a ridgeback or put the house up there. I can point to several houses in my neighborhood, including my own old abandoned driveway, that have significant rutting, to the point that I will no longer drive my car to one of my daughter's friend's houses. Sure I'll go in the 4x but the ride would be horrible if I towed the horses, I'd rather ride them up if I had to.

My suggestion is you talk to the excavator about bringing in a licensed civil engineer and reconfiguring the driveway altogether, which is what was done at my place. They ran it sideways and up the curve of the hill and back to the house, from the air it looks like a big question mark.

The excavator may have the practical experience, some are really good, but for potentially nasty driveways it's always nice to have a go-to guy.

SmartAlex
Jul. 20, 2010, 12:19 PM
Make it wide. One stable I know has a nightmare driveway. I can't tell you what the grade is, but I gulped when I saw it. On the way back up I put it in FWD and just went. Anyway, it does have a switch back and they go up and down with 7 horse slants all the time. The only problem I am aware of is one night with a little snow they had a commercial carrier trying to get out, and got the big truck stuck on the hill. Problem was, no one could get in or out until they got it out (well after mid-night). So I guess I'm saying, either have another way out, or make it wide enough that you can at least get around whatever is stuck.

slantedhorse
Jul. 21, 2010, 09:46 AM
The professional advice I have is to not go over a 12% slope .... trying to figure out if 12% is comfortable for most horse folk. The civil engineer can tell you what the guidlelines are but not what feels comfortable (in my experience anyway). The driveway will follow the curve of the hillside which is preferable to running it straight down the hill and it's not that long a distance so making a switchback would end up with hairpin turns.

ReSomething
Jul. 21, 2010, 12:21 PM
I'm figuring that one ranch I used to go to had close to 12%, and it takes some getting used to, although he trucked on up there with stock trailers full of cattle all the time. I drove up in a VW bug and it was a first gear in some spots, spitting gravel. God help you if you had to stop and get going again.

It definitely won't be fun in the snow and ice, or if you have vehicles that aren't in tip top condition.

SuperSTB
Jul. 21, 2010, 12:34 PM
It would take some getting used to and also take into consideration the connection to the road. (think long trailer on steep grade meets flat road and must turn on it. Keep in mind the hitch point)

Highways don't usually go beyond 6-7%, Most roads typically don't exceed 10%. Like ReSomething mentioned- it's not fun if you have to stop or start on a 12% grade.

SmartAlex
Jul. 21, 2010, 12:36 PM
The driveway will follow the curve of the hillside which is preferable to running it straight down the hill and it's not that long a distance so making a switchback would end up with hairpin turns.

OH No! I'm about to launch into stick art... The "switch back" the one I'm talking about had went like this...as viewed from the bottom, you traveled down the left grade... gradual turn and straight across the slope, then right turn to another grade. The straight across had a grade too to avoid catching the hitch on the lip (as in grade meets flat)


\
.\
..\________
................\
................. \
...................\

Which took advantage of two less sloping areas, and gave you a rest so the rig didn't get rollin'rollin'rollin'

Hilldale
Jul. 21, 2010, 09:05 PM
Slanted Horse -

The maximum design grade for a subdivision street on "rolling" terrain in Virginia is 10%. It sounds from your description that your excavator plans on just stripping the top soil and putting in your drive at grade. By doing this he avoids having to create ditches and deal with drainage. Whenever you have to cut to put a road in you need ditches to drain the water off the roadway to avoid rutting and washing in the road surface. I think 12% is too steep - especially if you don't plan on paving.

TBPNW
Jul. 21, 2010, 09:45 PM
I don't know the grade, but my driveway is an adventure in itself, steep with a hairpin turn. I was just pulling a 4 horse with one horse loaded, thinking I'd be fine on dry ground in 4 high. No, stalled out at the hairpin turn and had to get started from 4 low. I should've known, though. 4WD is a given- use it if you have it, even if you aren't pulling anything.