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Section 1  Preparing to Build
6.5.3 Finding Grade Level
Many points on the building site need to be
set at certain elevations or grade levels. These
points might include:
• The depth of excavation, such as for a
basement.
• The finished height (elevation) of the
foundation footings.
• The height (elevation) of foundation walls.
• The elevation of floors.
• Site features, such as proper grading to
ensure that surface water is directed away
from the building.
• Bearing elevation (point at which footings
contact the earth) for footings in order to
ensure adequate frost protection of the
foundation.
• Establishing rise and run of steps and
walkways as part of the exterior of the
structure.
Not all building sites are level. Finding the
difference in the grade level between several
points or transferring the same level from one
point to another is called grade leveling. This
operation is immediately useful to the exca-
vator, who must determine how much earth
must be removed to excavate a basement or
trench a foundation footing. Grade leveling is
also useful to determine how much earth must
be deposited in a particular area to achieve a
desired height or elevation at that location.
When the leveling instrument has been set
level, the line of sight will also be level. The read-
ings can be used to calculate the difference in
elevation, Figure 6-17. If the building site has a
large slope, the instrument may need to be set up
more than once between the points where you
want to take readings. The first reading is taken
with the rod in one position. Then, the instru-
ment is carefully rotated 180° to get the reading
at a second rod position. This position may be
higher or lower than the first position. From a
practical standpoint, it is simpler to work from
a higher point on the site than a lower point.
Depending on the actual slope, this measure-
ment can often be made with a single reading.
The term grade means the level of the ground.
Elevation refers to the major structural levels
of the building. More specifically, these levels
include the top of the footing, top of the founda-
tion wall, and finish height of the first floor.
There should be a reference point (level) for
all elevations established on the building site.
It is called the benchmark, datum, or simply
the beginning point. This point must remain
A
B
B
A
5'-2"
5'-9"
Figure 6-17. Establishing a grade level and finding the
difference between two points on a building lot. Top—
Level the instrument and take a line of sight reading on
point A. Mark down the rod reading. Bottom—Swing
the telescope 180° and take a line of sight reading on
the rod. Compare the two elevations. In this example,
point A is 7″ higher than point B.
Grade leveling:  Finding the difference in the grade
between several points or transferring the same level
from one point to another.
Grade:  Quality of lumber. Also, the height or level of
a building site.
Elevation:  The height of an object above grade. Also,
a type of drawing that shows the front, rear, and sides
of a building.
Datum:  An established reference point for deter-
mining elevations in an area. Also called benchmark or
simply the beginning point.