Chapter 6  Building Layout
153
If the building is small, such as a 24′ garage,
a carpenter’s level, line level, framing square,
and rule are accurate enough for laying out
and checking the building lines. But, as size
increases, special leveling instruments are
needed for greater accuracy and efficiency.
6.4.1 Leveling Instruments
The builder’s level and transit are more
accurate instruments for building layout. These
leveling instruments are frequently used in
construction work. They are basically telescopes
with accurate spirit levels and must be mounted
and leveled on a base that can be rotated. When
the job is too large for the chalk line, straight-
edge, level, and square, then leveling instru-
ments should be used.
The optical device of these instruments oper-
ates on the basic principle that a line of sight is a
straight line that does not dip, sag, or curve. Any
point along a level line of sight will be at the
same height as any other point. Through the use
of these instruments, the line of sight replaces
the chalk line, line level, and straightedge.
The builder’s level, also called a dumpy
level or optical level, is shown in Figure 6-5.
It consists of an accurate spirit level and a tele-
scope assembly attached to a circular base that
swivels 360°. Leveling screws are used to adjust
the base after the instrument has been mounted
on a tripod. The telescope is fixed so that it does
not move up or down, but it rotates on the base.
This permits any angle in a horizontal plane to
be laid out or measured.
The transit is like the builder’s level in most
respects, Figure 6-6. However, the telescope
can be pivoted up and down 45° in each direc-
tion. Using this instrument, it is possible to
accurately measure vertical angles. The transit
is also used to determine if a wall is perfectly
plumb (vertical) by sighting the vertical cross-
hair while pivoting the scope up and down. Its
vertical movement also simplifies the operation
of aligning a row of stakes, especially when they
vary in height.
In use, both the builder’s level and transit are
mounted on tripods, Figure 6-7. Some models,
Carpenter’s level:  Tool used for laying out and
checking the building lines.
Builder’s level:  An optical device used by builders to
determine grade levels and angles for laying out build-
ings on a site. Also called a dumpy level or an optical
level.
Transit:  Optical leveling instrument commonly used
for building layout.
Line of sight:  A straight line that does not dip, sag,
or curve. Any point along a level line of sight is at the
same height as any other point.
Plumb:  Exactly perpendicular or vertical; at a right
angle to the horizon or floor.
90°
8'-0"
6'-0"
10'-0"
Figure 6-4. To check whether a corner is square, mark
6′ along one building line and 8′ on the intersecting
building line. If the distance between the marks is 10′,
the corner is square.
Instrument
level vial
Eyepiece
Horizontal
tangent screw
Horizontal
clamp screw
Leveling screws
Horizontal
graduated circle
Lens
Figure 6-5. The builder’s level is used to sight level
lines and lay out or measure horizontal lines. (David
White)