Most New Zealand councils compare the grade of driveways on submission documents to the guidelines to gradients in their standards or the national standards typically 1in5 or 1in6. However you may encounter sites that due to the topography cannot be accessed with driveways at these grades.
Raising the question what is the maximum grade a driveway can be constructed at to provide access to a property? To answer this I have measured the grade of a few driveways around town that people seem to be quite happily using. Here are some pictures to assist you with making the extreme happen when you need too. Note Drainage and surface finish are two areas that care need to be taken in as well as ice and snow if this is applicable.
31.3 % (1V:3.19H)
34.8% (1V:2.87H)
31.3% (1V:3.19H)
31.9% (1V:3.13H)
33.5% (1V:2.98H)
and a couple of local public roads for good measure
30.4% (1V:3.29H)
29.1% (1V:3.44H)
Great post Justin!
ReplyDeleteYep, NZers want to build everywhere, and if some people say it can't be done, we'll go out and prove them wrong.
=)
Justin, thanks for the post.
ReplyDeleteWe did a topo recently where the driveway was as steep as 1:2.8 (No wonder I felt pooped walking up it). It seemed to work ok.
Safety is an obvious problem with these grades. There's the obvious issues with maintaining traction when it's icy. I also saw a 4WD get in trouble on a steep drive once due to wet leaves on the drive which meant the wheels locked up under braking and just kept sliding down the hill. (It was a slow and rather graceful journey to the bottom of the drive).
Michael
Michael
ReplyDeleteGood tip on the leaves, the level was sliding in places 1;3 is about as steep as you want to go. Always discussing the issue down here so throught it would be good to have some pictures and reference for people to refer too. Most of the driveways in the pictures are in the shadow of Queenstown Hill in the winter so will ice up over winter so people just park on the road. I guess a second access by stairs to the houses would be a good design feature.
Great little blog, enjoyed looking at the pictures Driveway paving Shenfield
ReplyDeleteI don't understand your angles of slop. why would you give it as a %, wouldn't it be better as a degree. Example is your last image, 29.1% 1v : 3.44 h. That is a 16.2 degree of angle. Sounds much better than 29%. I think anything about 20 degrees is getting to the upper limits of safety but I have driven on steeper driveways, one on Waiheki Island.
ReplyDeleteIts common civil engineering road geometry design terminology to talk about road slopes in the terms of % grade. Hence the use of % above
ReplyDeleteThanks for sharing the blog. Paving Rhode Island
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