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Thread: Impervious surface calculations

  1. #1
    Member
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    Impervious surface calculations

    I am calculating[I] impervious lot coverage for a piece of property and would like to know the following: if the eaves of the roof go out over the driveway (say at the garage) do you count the driveway area under the eaves or leave that out of the calculation?

    Also, are 8" thick retaining walls to be included in the impervious calcs?
    Last edited by theahab; 31 Aug 2011 at 10:46 PM.

  2. #2
    Cyburbian Tarf's avatar
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    Check your municipal code - it should provide guidance.

    If not, eaves are usually considered part of the impervious surface area. However, if an eave is projecting over a PAVED driveway, make sure not to double count that area (since both eaves and driveway = impervious, barring any special driveway material like grasscrete).

    Hope that helps.

    Edit: And yes, 8" thick retaining walls are definitely impervious, though again consult the municipal code.
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  3. #3
    Cyburbian ColoGI's avatar
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    Quote Originally posted by tarf12345678 View post
    Check your municipal code - it should provide guidance..
    Especially up there. Few places do not have this well-covered.

  4. #4
    Unfrozen Caveman Planner mendelman's avatar
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    General rule of thumb anywhere - if it's paved it's impervious.
    I'm sorry. Is my bias showing?

    Let's not be didactic in this profession, because that is a path to disillusion and irrelevancy.

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  5. #5
    Cyburbian mike gurnee's avatar
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    Use common sense and make it easy to administer... and put your determination in writing. Few codes will address such issues.

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