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Grading

Discussion in 'Residential Foundation Codes' started by Keystone, Jan 27, 2012.

  1. Keystone

    Keystone Sawhorse

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    2009 IRC - R401.3 Drainage. Surface drainage shall be diverted to a storm sewer conveyance or other approved point of collection that does not create a hazard. Lots shall be graded to drain surface water away from foundation walls. The grade shall fall a minimum of 6 inches (152 mm) within the first 10 feet (3048 mm).

    Exception: Where lot lines, walls, slopes or other physical barriers prohibit 6 inches (152 mm) of fall within 10 feet (3048 mm), drains or swales shall be constructed to ensure drainage away from the structure. Impervious surfaces within 10 feet (3048 mm) of the building foundation shall be sloped a minimum of 2 percent away from the building.

    When a home or a free standing addition to a home rests on piers and the bottom plate of the home is 3" above grade (no floodplain) would section 401.3 apply?
     
  2. gbhammer

    gbhammer Platinum Member

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    Is the grade sloped away from the pier? The pier is your foundation.
     
  3. Mark K

    Mark K Platinum Member

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    The intention is to keep surface runoff from gaining access to the habital spaces. You would not want water to pond under the house.

    If these objectives are met I would see no problem with water flowing under the house.
     
  4. Francis Vineyard

    Francis Vineyard Sawhorse

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    Keystone, I believe you meant to say the sill is 3' above grade; whether your AHJ enforces Property Maintenance Code;

    302.2 Grading and drainage. All premises shall be graded and maintained to prevent the erosion of soil and to prevent the accumulation of stagnant water thereon, or within any structure located thereon.

    The section that Mark K is refering to:

    R408.6 Finished grade. The finished grade of under-floor surface may be located at the bottom of the footings; however, where there is evidence that the groundwater table can rise to within 6 inches of the finished floor at the building perimeter or where there is evidence that the surface water does not readily drain from the building site, the grade in the under-floor space shall be as high as the outside finished grade, unless an approved drainage system is provided.

    Francis
     
  5. Keystone

    Keystone Sawhorse

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    Existing home with framed freestanding addition on piers, bottom plate is 3" from existing grade in rear and 6" at the front of freestanding addition.
     
  6. jar546

    jar546 *****istrator

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    How can your framing meet the minimum distances to earth for decay if it is only 3" above grade?
     
  7. Keystone

    Keystone Sawhorse

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    Jar please, I may go absent minded from time to time but this mess is not my framing. This is a location with a previous inspector having several issues come to life.
     

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