We’ve described in previous articles how design and cost estimating often connect, but for the engineer or estimator reading through a drawing, the process can be daunting.
If you’re not sure where to start with understanding the project from the drawings, use the non-comprehensive list below to give yourself a head start in advance of any measurements or takeoffs.
I. Feasibility Study (FS) / Programming Phase
At this earliest stage, conceptual estimates are the most likely outcome of your work. The initial documents set the project’s fundamental parameters. A quick review provides crucial context for the eventual final estimate.
Gross Square Footage (GSF) or Total Area
Why it’s Important: This sets the high-level scale of the project and sets the foundation for conceptual estimates.
Where to Look: A good feasibility study will have a Project Program or Initial Site Plan Document. It can sometimes be displayed as a simple table on a cover sheet.
Target Construction Type
Why it’s Important: The entire cost structure and schedule depend on the intended building material and style.
Where to Look: This should be found in the Project Narrative or Program Document, often referenced as Type I-A, Type V-B construction (can depend on prevailing building codes).
II. Schematic Design
At this stage of the design, the drawing should establish the major spatial relationships and system selections. Even though these drawings typically only represent 15-20% of the design completion, there are still a few critical elements a good drawing will contain at this stage.
Building Footprint and Height
Why it’s Important: These define the major structural and envelope costs. The footprint is used to calculate foundations and roofing areas. The height impacts vertical material conveyance and structural design.
Where to Look: Floor plans (often single-line diagrams) and building elevations; also building section drawings.
Primary Structural System
Why it’s Important: Knowing the core structure (e.g., concrete shear walls vs. steel moment frame) is necessary to determine the basic shell cost.
Where to Look: Structural plans; sometimes referenced in architectural plans as a note or in a preliminary structural key plan.
Major Mechanical/Electrical Rooms
Why it’s Important: The size and location of areas dedicated to primary MEP equipment (boilers, chillers, electrical gear) dictates space allowances, which in turn affect the GSF and structural support needs.
Where to Look: Preliminary Floor Plans (look for rooms labeled “MECH,” “ELEC,” or “TEL/DATA”).
III. Design Development (DD)
At this stage of the design, the drawings should be significantly more detailed. There should be clear definition of size, shape and material of major building components. Even though these drawings typically only represent 50-60% of the design completion, estimators and engineers can begin making strong assumptions about final construction requirements.
Exterior Envelope Materials
Why it’s Important: This includes cladding (e.g., brick, curtain wall, metal panels). These materials have a big cost impact and can significantly affect the schedule.
Where to Look: Elevations (with specific material hatch patterns and notes) and wall sections (for material layering).
Dimensioning and Grid Lines
Why it’s Important: Consistent and verified dimensions are critical for takeoffs. Checking the structural grid against architectural elements is necessary to ensure constructability and prevent dimensional errors in your quantities.
Where to Look: Dimensioned floor plans (architectural and structural); verify dimensions across different sheets.
Preliminary Door/Window Schedules
Why it’s Important: These schedules start defining the quantity, size and type of openings, which are necessary for calculating the cost of doors, frames, hardware and glazing.
Where to Look: Door/window schedules (often on the A-series sheets); cross-reference with floor plans and elevations.
IV. Construction Documents (CD)
These are the final, coordinated drawings that may be used for permitting and construction. They are typically 95-100% complete on receipt and should be the primary source of all quantity takeoffs for a construction project.
Cover Sheet, Drawing Index, and Sheet Revisions
Why it’s Important: The index tells you which drawings exist, the revision history ensures you are working with the latest scope, and the cover sheet often contains the official project statistics (areas, code analysis).
Where to Look: The A0.0 or G-series sheets (cover sheet/general notes). Always check the revision block/triangle on every sheet.
Detailed Specifications
Why it’s Important: The drawings show where a material goes; the Specifications indicate the quality, manufacturer, model number, and installation standards. Costs must reflect the specific quality mandated by the specifications.
Where to Look: The Specifications Document (separate from the drawings, organized by CSI MasterFormat sections). Never estimate without reviewing the relevant sections.
Not sure how to read specifications? Check out our quick guide to construction specifications.
General Notes, Key Notes, and Abbreviations
Why it’s Important: These contain critical instructions and assumptions that affect cost, such as required demolition, site work requirements, owner-furnished/contractor-installed items (OFI/CI) or performance requirements.
Where to Look: G, C, A, S, M, P, E-series sheets; look for large blocks of text titled “GENERAL NOTES,” “SCOPE,” or a “KEY NOTES” diagram/list.
Sections and Details
Why it’s Important: These drawings show the complex junctions and assemblies. They are essential for accurate quantity surveying of hidden, high-cost materials like flashing, waterproofing, specialized connections and insulation.
Where to Look: A-series sheets (architectural sections/details) and S-series sheets (structural details). Look for the detail bubbles on plans that refer you to the correct sheet.
Schedules
Why it’s Important: Schedules organize the quantifiable count and specific attributes of repetitive elements. This is where you get your unit counts for items like light fixtures, plumbing fixtures, room finishes (flooring, paint) and hardware sets.
Where to Look: A-series (finishes/doors/millwork) and M/P/E-series (equipment/fixtures).
This list of critical elements is by no means comprehensive. Learning to accurately read and analyze construction drawings can be a lifetime endeavor. If you find yourself frequently dealing with the difficulty of connecting drawings and takeoffs to cost estimates, you should take a look at the innovative approach enabled by Gordian’s eTakeSync product, which integrates your estimates with eTakeoff and vise-versa.
