Kanga Metrics
Before you can price a project accurately, as a contractor you must first understand exactly what is being built.
Many losses occur long before construction begins. They occur during tendering when drawings are misunderstood or critical details are overlooked.
A contractor who misinterprets a drawing is effectively pricing a different project from the one that will eventually be built.
This chapter explains how contractors should approach construction drawings.
The Purpose of Drawings
The primary purpose of construction drawings is to detail and communicate design intent.
They provide information regarding:
- Dimensions
- Materials
- Locations
- Quantities
- Construction details
Drawings form part of the contract documents and should never be reviewed in isolation.
They must always be read together with:
- Specifications
- Bills of Quantities
- Conditions of Contract
- Schedules
Architectural Drawings
Architectural drawings focus primarily on functionality and appearance.
Common architectural drawings include:
Site Plans
These show the location of structures on the site.
Key information includes:
- Building position
- Access roads
- Boundaries
- Existing structures
- Utilities
Floor Plans
Floor plans provide a horizontal view of the building.
Contractors should review:
- Room layouts
- Wall locations
- Openings
- Dimensions
Elevations
Elevations show external views of the structure.
These help identify:
- Finishes
- Heights
- Architectural features
Sections
Sections reveal information hidden from plan views.
They often contain critical information relating to:
- Foundations
- Floor build-ups
- Roof structures
Structural Drawings
Structural drawings explain how the building will carry loads safely.
Contractors must pay special attention to:
- Reinforcement details
- Concrete grades
- Structural steel requirements
- Connection details
Structural omissions during tendering often become expensive variations during construction.
Services Drawings
Services drawings include:
- Mechanical systems
- Electrical systems
- Plumbing systems
- Fire protection systems
Contractors should carefully identify coordination requirements between services and structural elements.
Failure to do so often results in rework and delays.
Common Drawing Review Mistakes
Many contractors make the following mistakes when it comes to reviewing drawings:
Looking Only at the BOQ
The BOQ should never replace drawing review.
Ignoring Notes
Critical information is frequently contained in notes rather than graphics.
Reviewing Drawings Independently
Contractor’s must ensure that engineers, and project managers should participate in drawing reviews.
Assuming Missing Information
Assumptions create risk. Whenever information is unclear, requests for clarification should be submitted before tender close.
A Practical Drawing Review Process
Step 1: Review all drawings.
Step 2: Review specifications.
Step 3: Compare drawings against BOQ.
Step 4: Identify discrepancies.
Step 5: Raise clarification requests.
Step 6: Document assumptions.
Step 7: Update pricing accordingly.
Key Lessons
- Drawings are legal contract documents.
- Drawings must always be reviewed together with specifications and BOQs.
- Assumptions create risk.
- Thorough drawing review improves estimate accuracy.
- Understanding scope is the foundation of project success.
A contractor who understands the drawings thoroughly before pricing is already ahead of most competitors.
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