How to read a grade rod

Written by jen randall
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How to read a grade rod
Earth is levelled to an even grade prior to construction by reading a grade rod. (Hemera Technologies/AbleStock.com/Getty Images)

The earth is hardly flat, and surveyors in construction overcome this in building projects by flattening the ground into a specific level, or grade, using tools such as a grade rod. Used with a level and grade stakes, a grade rod measures the difference between the elevation of the ground and the prescribed grade elevations. Though grade rods are of many types and levels of sophistication, all determine whether land needs to be filled or cut. Reading a grade rod reveals the difference between the existing grade and the prescribed grade elevation.

Skill level:
Moderately Challenging

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Things you need

  • Stakes
  • Lumber crayon (keel)
  • Pencil and paper
  • Grade rod or stick and measuring tape

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Instructions

  1. 1

    Set up as constant the Height of Instrument (HI) using a measuring tape. This is the constant level of view in a surveying project. Determine the exact HI and write it down.

  2. 2

    Determine the prescribed or desired grade elevation for the project, based on specifications determined about the construction project or irregularities in the land (such as a watershed, rocks or other geographical points).

  3. 3

    Insert grade stakes into the ground. Depending on how uneven the ground is compared to the prescribed or desired grade elevation, many or few stakes may be used.

  4. 4

    Mark the desired grade elevation on the stakes using the lumber crayon (keel).

  5. 5

    Calculate the difference between the desired grade elevation and the HI. The grade rod can be read by using a rod that comes with a level to get the most exact measurement, or it can be read by using a stick and measuring tape.

Tips and warnings

  • If the difference between the prescribed elevation and the Height of Instrument is a negative number, it means that the earth needs to be cut or removed, not filled.
  • Grading can be simple or complicated depending on the construction project. Consult a general contractor or professional surveyor to ensure you are using proper techniques to find the Height of Instrument and other measurements before building.

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