grade plane elevation. A reference plane representing the average of
 finished ground level adjoining the building at exterior walls. Where the
 finished ground level slopes away from the exterior walls, the reference plane
 shall be established by the lowest points within the area between the building
 and the lot line or, where the lot line is more than 6 feet (1829 mm) from the
 building, between the building and a point 6 feet (1829 mm) from the building.

 Since the finished ground surface adjacent to the building may vary
 (depending on site conditions), the mean average taken at various points
 around the building constitutes the grade plane. In the context of the code,
 the term “grade”  means the finished ground level at the exterior walls. While
 the grade plane is a hypothetical horizontal plane derived as indicated by
 Figure (1), the grade is that which actually exists or is intended to exist at
 the completion of site work.

 Situations may arise where the ground adjacent to the building slopes away
 from the building because of site or landscaping considerations. In this case,
 the lowest finished ground level at any point between the building’s exterior
 wall and a point 6 feet (1829 mm) from the building [or the lot line, if closer
 than 6 feet (1829 mm)] comes under consideration. These points are used to
 determine the elevation of the grade plane as illustrated in Figure (2) and
 Figure (3).

 The only situation where the grade plane and the grade are identical is when
 the site is perfectly level for a distance of 6 feet (1829 mm) from all exterior
 walls.

 Figure (1). DETERMINATION OF GRADE PLANE ELEVATION WHEN GRADE SLOPES
      UNIFORMLY ALONG THE ENTIRE LENGTH OF THE EXTERIOR WALLS
 
AVERAGE GRADE ELEVATION AT EACH EXTERIOR WALL:
NORTH: 496.5' WEST: 494.25 SOUTH: 491.0' EAST: 493.25'
      AVERAGE GRADE ELEVATION = [496.5'+494.25'+491.0'+493.25']÷4=493.75'
Figure (2). DETERMINATION OF GRADE PLANE WHERE GRADE SLOPES AWAY
     FROM THE EXTERIOR WALL

 THE GRADE ELEVATION THAT IS USED IN DETERMINING THE
       GRADE PLANE ELEVATION = 487.5'.

 

Figure (3). DETERMINATION OF GRADE PLANE ELEVATION WHERE GRADE DOES NOT
     SLOPE UNIFORMLY ALONG THE LENGTH OF THE EXTERIOR WALLS

AVERAGE GRADE ELEVATION AT EACH EXTERIOR WALL:
NORTH: [(496.5' + 496.5']/2 = 496.50'
WEST: [496.5' + 490.0']/2 = 493.25'
SOUTH: [490.0' + 488.0']/2 = 489.00'
EAST: [496.5' + 488.0']/2 = 492.25'

 NORTH: 496.50' WEST: 493.25 SOUTH: 489.00' EAST: 492.25'
     AVERAGE GRADE ELEVATION = [496.50'+493.25'+489.00'+492.25']÷4=492.75'
 

   

All Rights Reserved. This 2006 International Building Code® is a copyrighted work owned by the International Code Council, Inc. Without advance written permission from the copyright owner, no part of this book may be reproduced, distributed, or transmitted in any form or by any means, including, without limitation, electronic, optical or mechanical means (by way of example and not limitation, photocopying, or recording by or in an information storage retrieval system). For information on permission to copy material exceeding fair use, please contact: Publications, 4051West Flossmoor Road, Country Club Hills, IL 60478-5795. Phone 1-888-ICC-SAFE (422-7233). Trademarks: “International Code Council,” the “International Code Council” logo and the “International Building Code” are trademarks of the International Code Council, Inc.