Construction Drawing Interpretation for Building Measurement

Posted on Sep 13, 2025 in Design and Engineering

Interpreting Construction Drawings & Specifications

Measuring Concrete Slabs: Essential Drawings

To measure concrete in a slab on ground for a two-storey home, you would typically use the following drawings from a standard set:

  • Site Layout Plan
  • Section Drawing
  • Engineer’s Slab Drawing (if available)

Classifying Construction Drawings

Regarding the selected drawings:

  • The Site Layout Drawing is a plan that shows the perimeter of the building.
  • A Section Drawing provides a section view of the house. If an engineer’s slab section drawing is available, it should be used instead.

Identifying Aluminum Windows in Project Plans

To identify the aluminum windows for the same project, refer to:

  • Elevation Drawings: Elevations 1, 2, 3, and 4 typically show dimensions and glazing details.
  • Specifications: These provide detailed information, for example, ‘Elevation 3 shows 6.38mm Laminated glazing with Q-Lo…’
  • Window Schedule: This lists all window types and specifications.

Note: Elevation 4 is often a primary source of information for window details.

Window Specifications: Number, Size, Frame, Glass

To fully describe the windows in terms of the number required, their size, frame, and glass type, you would refer to:

  • Elevation Drawings: These indicate the number, size, and glass type.
  • Specifications: May include tradenames and specific material details.
  • Window Schedule: Lists window types, frame materials, and installation details.

Interpreting Project Plans and Specifications

Determining Roof Frame Members & Dimensions

To measure roof frame members, you would take the upper floor plan, which shows the roof outline dotted. To determine the required members and their dimensions:

  1. The first point of check should be the specifications.
  2. If member sizes and required members are not outlined, or if engineer-designed drawings are not specified, then use the Timber Framing Code to determine the dimensions, required members, and bracing/fixing requirements.

Interpreting Levels, Heights, and Gradients

Calculating Stud Height from Drawings

To determine the height of studs:

  1. Refer to an Elevation Drawing that indicates the Finished Ceiling Level (FCL) and Finished Floor Level (FFL) of each storey.
  2. To find the height of a particular storey, subtract the FFL from the FCL of that storey.
  3. Then, further subtract the depth of both the top plate and bottom plate. (These depths can be found in the project specifications or the Timber Framing Code).

Determining Soil Depths for Excavation

To determine levels for the calculation of soil depths for excavation:

  1. Determine where the Benchmark is or set up a Temporary Benchmark (TBM) according to land survey instructions.
  2. Dig a narrow test hole and place a marking stick at the bottom to indicate the initial excavation depth.
  3. Follow the general rise and fall of the contour, excavating in several depth layers or ‘runs’.
  4. Each time, use a laser level to measure the level after each run of excavation.
  5. Work out the level by using the site plan’s contour lines and spot levels, then calculate the depth.

Quantity Take-Off: Standard Industry Practice

Calculating Soil Quantity for Strip Footings

To determine the quantity of soil to be excavated in strip footing trenches:

  1. Follow the requirements of AS 2860 (Slabs and Footings) or relevant local standards.
  2. Determine the required depth of excavation along the edge of the slab and intermediate supports using contour lines and spot points on the site layout plan.
  3. Site classification and footing design by an engineer will indicate the exact depth of the footing.
  4. Calculate the volume of the strip footing trenches from the drawings mentioned above to determine the ‘banking volume’ (volume in situ).
  5. Allow a percentage increase for ‘bulking’ to account for the expansion of soil and the presence of unexpected larger rocks once excavated.