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Thread: What are acceptable slopes on a lot?

  1. #1
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    What are acceptable slopes on a lot?

    Greetings....need opinions on what one could consider the (upper limit) norm for slopes over plots? Looking to achieve 20 percent slopes over plots in some areas of a newly created hillside terrace.

    Civil/geotech appointment is a way off but we need to finalise design intent of a new hillside terrace precinct- looking to go over 50m height in places.

    Plot size is around 30m deep x 17m wide.

    Anyone been carving up hillsides lately?

  2. #2
    Cyburbian abrowne's avatar
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    If the locals are used to slopes then 20% is reasonable over a lot, so long as there remains a buildable envelope. No-disturb covenants and other hillside regulations should also apply.

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    thanks...we have to be careful that the locals can easily negotiate the roadways up to each plot (nice catch ...they are not used to hills)....but once on their own plot, they buy into spectacular views/ elevated living.

    Quote Originally posted by abrowne View post
    .. then 20% is reasonable over a lot, so long as there remains a buildable envelope. No-disturb covenants and other hillside regulations should also apply.....
    Any precedent that I can look at?
    Last edited by Gedunker; 07 Oct 2008 at 8:16 AM. Reason: seq. posts

  4. #4
    Cyburbian Emeritus Chet's avatar
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    In most codes I've administered, 10% street slope and 12% lot slope is generally the maximum. This is based on local soil characteristics and a regional effort to preserve slopes as a desired natural feature.

  5. #5
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    Have you Googled hillside protection zoning codes ?
    Oddball
    Why don't you knock it off with them negative waves?
    Why don't you dig how beautiful it is out here?
    Why don't you say something righteous and hopeful for a change?
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    Cyburbian Jeff's avatar
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    Around here pretty much anywhere i've ever done work in has the same requirements for overland slope:

    Min = 1.5%
    Max = 3:1 (33%)

    When doing a grading plan, if it is a lot with a steep drop-off, and I used 3:1 slopes to catch grade, I do like to provide some usable yard area. Generally around 10' front and sides, 20' rear. you don't want to go 3:1 right from the house.

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    awesome everyone, thanks for the feedback

  9. #9
    Make sure you talk with your public safety people: getting a fire truck up a road with a 20% grade is no mean feat.

    Off-topic:
    Do you call them trucks or lorries in Oz?

  10. #10
    Cyburbian Jeff's avatar
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    The 20% referenced above, i believe is for overland. Not roads....of which I typically limit, unless told otherwise, to 10%

    The "manayunk wall" for any of you who follow bike racing, is down the street from me, and tops out at 23% grade. It's a 2 way 24' wide road, with parking on both sides

  11. #11
    Cyburbian Rem's avatar
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    20% and then you go to special construction types (eg. pole houses).

    There are some guidelines and design suggestions here: http://www.lakemac.com.au/page.aspx?...778&ftype=True. Open the download and go to 2.1.9. "Sloping Land and Soil" starts on page 54.

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    Quote Originally posted by Gedunker View post

    Off-topic:
    Do you call them trucks or lorries in Oz?
    ...call them utes.

    Thanks all for your replies. We managed to kickstart some life into the Quantity Surveyor.....

  13. #13
    Cyburbian Streck's avatar
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    A 10% cross slope is pretty steep.

    On a 10 wide parking space with a 10% cross slope this would be one foot in ten, or a 12 inch vertical height difference between parking space lines.

    A typical car wheel is about 24 inches in diameter, so that would be to the center of the wheel to give a visual perspective.

    A front to rear slope of 10% would be a 24 inch difference in a 20 foot long space.

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    ok...for areas where there is no traffic or vehicle access, I'm working on 20 percent slope front to back on a 30m (98') deep house lot.
    The plot gets sold as is- and engineered by the purchaser with restrictions on allowable cut and fill with minimum percentages of slope left in a 'natural' state. It is a man made hill after all

  15. #15
    Cyburbian abrowne's avatar
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    re: Comment above about 20% slope requiring pole houses

    This is really not the case at all. You can have a walk-out basement on one side, kind of a 1.5 storey setup. Definitely no need for engineered pole houses.

  16. #16
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    Here's a quick graphic I did for a hillside zone review:

    http://farm4.static.flickr.com/3154/3039324780_067956eee5.jpg

    At between 15% - 20%, the difference in elevation between the front and rear of the home is about 1 storey, which allows for walk-out basements to happen. This is also, coincidentally, a nice slope that can be achieved without significant earthworks or retaining walls. Getting beyond this though, you start dealing with having to push dirt about more significantly, which leads to visual scarring and all that other lovely stuff.

    Other things to consider hillside wise is the depth of front setback (keep it minimal), how parking is handled (make it from edge-of-pavement, not edge of lot line) and allowable continuous vertical surfaces (think about big, blank walls shooting up several stories from the downslope perspective) versus terraced effects for retaining walls and buildings.

  17. #17
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    Great feedback- thanks

    Quote Originally posted by spatialmongrel View post
    Here's a quick graphic I did for a hillside zone review:

    http://farm4.static.flickr.com/3154/...067956eee5.jpg

    At between 15% - 20%, the difference in elevation between the front and rear of the home is about 1 storey, which allows for walk-out basements to happen. This is also, coincidentally, a nice slope that can be achieved without significant earthworks or retaining walls. Getting beyond this though, you start dealing with having to push dirt about more significantly, which leads to visual scarring and all that other lovely stuff.

    Other things to consider hillside wise is the depth of front setback (keep it minimal), how parking is handled (make it from edge-of-pavement, not edge of lot line) and allowable continuous vertical surfaces (think about big, blank walls shooting up several stories from the downslope perspective) versus terraced effects for retaining walls and buildings.

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