Site Set Out Flashcards
What is an offset line in construction set out?
A line that is set up parallel to the boundary line in a location closer to the building’s intended location.
Why is an offset line set up parallel to the boundary line?
To maintain a consistent relationship and distance from the boundary.
In what location relative to the intended building location is an offset line typically placed?
Closer to the building’s intended location.
Give one reason why an offset line might be used during site set out.
When the boundary line is a great distance from the building location.
What type of site condition might necessitate the use of an offset line?
Obstructions preventing the boundary line from being pulled straight through.
If the boundary line is far from the building, why is an offset line helpful?
It provides a more practical and accessible reference closer to the work area.
How do obstructions on a site influence the decision to use an offset line?
They make it difficult or impossible to directly use the boundary line for setting out.
What is the primary benefit of using an offset line when the boundary is obstructed?
It allows for accurate setting out despite the obstruction.
What is a datum in the context of construction levels?
A fixed, known, and permanent reference point used as a basis for measuring all elevations.
What are the three key characteristics of a datum mentioned in the text?
Fixed, known, and permanent.
What serves as the “zero point” for the vertical scale of a build?
The datum.
What does RL stand for in construction?
Reduced Level.
How is the Reduced Level (RL) defined?
The height of a specific point on the construction site relative to the datum.
What is the relationship between RL and the datum?
RL is the vertical distance (above or below) measured from the datum.
What does the numerical value of an RL represent?
The vertical distance of a point above or below the datum point.
Give one example of a specific point in a build where the RL might be set.
The finished floor level (FFL).
Name two other examples of points where an RL is typically specified.
Foundation height, a point on a retaining wall.
Is the datum itself a numerical height value?
No, the datum is the zero point for the vertical scale.
On what type of consented drawings is the datum usually indicated?
The site plan or typographical survey.
Name one specific drawing where you would likely find the project datum.
Site plan.
What are some examples of physical features that can be used as a datum on or adjacent to a site?
Manhole covers, a steel pin embedded in a footpath.
Name one specific man-made feature mentioned that can serve as a datum.
Manhole cover.
Describe the appearance of a steel pin embedded in a footpath that might be used as a datum.
Usually a metal disc found in the ground.
What is another common metal object found in the ground that can act as a datum?
A steel pin embedded in a footpath (metal disc).
What is the purpose of contour lines on construction drawings?
To represent the shape of the land.
What aspect of the land do contour lines represent?
Elevation or height.
How do closely spaced contour lines indicate the terrain?
A steep slope.
What does a wide spacing between contour lines suggest about the slope of the land?
A gentle slope.
What is another common name for a dumpy level used on construction sites?
Builders level.
Describe the initial step in setting up a dumpy level on site.
Choose a spot on site with firm ground and adequate line of sight.
What is the purpose of extending the tripod legs when setting up a dumpy level?
To provide a stable base and achieve a comfortable working height.
How is the dumpy level secured to the tripod?
It is mounted onto the tripod.
What part of the dumpy level is adjusted to roughly level the instrument?
The tripod legs (until the bubble is centered)
How is the final, precise leveling of a dumpy level achieved?
By adjusting the leveling screws until the bubble is centered.
What is the purpose of focusing the eyepiece of a dumpy level?
To make the staff readable and clear.
What type of surface is ideal for placing a laser level?
A stable surface.
Besides a stable surface, what other mounting option is common for laser levels?
A tripod.
What setting on a laser level helps it achieve a level beam automatically?
Auto-level settings.
What might be used in conjunction with a laser level to detect the beam?
A laser detector set up on the staff.
Name the third type of levelling equipment mentioned.
Spirit Level.
Describe the first step of the two-peg test for a dumpy level.
Set two pegs about 20m apart.
What is measured in the second step of the dumpy level accuracy check?
The level of the pegs with the staff, with the dumpy set up midway between them.
Where is the dumpy level relocated for the third step of the accuracy check?
2m past the pegs in a line.
What is compared to determine if there’s a discrepancy in the dumpy level readings?
The difference between the measurements taken from the two different dumpy level positions.
How is the accuracy of a rotating laser level checked using a wall or fence?
By marking the center of the laser, rotating the laser 180 degrees, and marking the center again.
What action is performed with the laser level on the tripod during its accuracy check?
It is rotated 180 degrees.
What measurement indicates the discrepancy in a rotating laser level’s accuracy?
The distance between the two marks made on the wall or fence.
Where should profiles be placed relative to the excavation area?
Outside of the excavation area.
What is a crucial requirement for the line of sight from profiles?
It must be clear and unobstructed.
Why is it important to place profiles in stable ground?
To prevent movement and maintain accurate references.
