(A) Shown below are minimum thickness of base and surface course to be used. Design should be chosen from Group 1 or Group 2 depending on subgrade soil type.
GROUP I | ||
Good to Excellent Subgrade Soil Types | Base Course | Pavement Surface |
GROUP I | ||
Good to Excellent Subgrade Soil Types | Base Course | Pavement Surface |
A-1-a, A-1-b, A-3, A-2-4, A-2-5, A-2-6, A-2-7 | 7 inches STBC, Type A or C | 2 inches SA or I-1 |
9 inches STBC, Type A or C | 1-1/2 inches SA or I-2 | |
8 inches ABC or TBC, Type B | BST, 1 inch SA or I-2 | |
6 inches ABC or STBC, Type B | 1-1/2 inches SA or I-2 | |
3 inches BCBC, Type HB | 1-1/2 inches SA or I-2 | |
3 ½ inches BCBC, Type HB | 1 inch SA or I-2 | |
5 inches plain concrete | ||
GROUP II | ||
Poor to Fair Subgrade Soil Types | Base Course | Pavement Surface |
GROUP II | ||
Poor to Fair Subgrade Soil Types | Base Course | Pavement Surface |
A-4, A-5, A-6, A-7-5, A-7-6 | 9 inches STBC, Type A or C | 2 inches SA or I-2 |
8 inches ABC or STBC, Type B | 1-1/2 inches SA or I-2 | |
10 inches ABC or STBC, Type B | BST, 1 inch SA or I-2 | |
4 inches BCBC, Type HB | 2 inch SA or I-2 | |
3 inches BCBC, Type HB | 6 inches plain concrete | |
Note: | ||
Subgrade No base course shall be placed on muck, pipe clay, organic matter or other unsuitable material. The District Engineer may require a subgrade soils test, if needed, to determine the soils classification type. | ||
ABC Aggregate Base Course, No. 7 stone | ||
STBC Soil Type Base Course | ||
BST Bituminous Surface Treatment | ||
SA Bituminous Concrete Surface Course, Type F-1 (Sand Asphalt) | ||
I-2 Bituminous Concrete Surface Course, Type I-2 (Note: I-1 may be used in lieu of I-2) | ||
BCBC Bituminous Concrete Base Course, Type HB (Black Base) | ||
(B) Any other pavement design must be reviewed by the Planning Board on an individual basis and approval will be based upon sound engineering principles.
(C) Other base courses such as various cement-treated materials may be used in lieu of those shown above. These materials shall be of sufficient thickness to provide equivalent strength. However, any design other than those shown above must also be approved prior to use.
(D) All materials shall meet the requirements set forth in the latest edition of the North Carolina Standard Specifications for Roads and Structures.
STREET DESIGN DIAGRAMS
ACCORDING TO NCDOT
MINIMUM CONSTRUCTION STANDARDS
JANUARY 1, 2010 (Revised July 2020)