Understanding Engineering Drawings: How to Read Them Like a Builder
Engineering drawings are not just “a set of plans”. They are a contract instruction and a risk control tool. The best builders treat engineering documentation the way pilots treat checklists: follow it, verify it, and record it.
1. The Three Things to Check Before You Build Anything
- Revision: confirm you have the latest issue and that site is building off that set.
- Scope boundary: know what the engineer has designed (and what they haven’t). Interfaces are where mistakes occur.
- Notes: general notes often contain critical constraints (materials, assumptions, site class, durability exposure).
2. How to Read Schedules (The Fast Way)
- Beam/lintel schedules: size, grade, number of plies, bearing requirements, fixings.
- Reinforcement schedules: bar sizes, spacing, lap lengths, and anchorage requirements.
- Connection details: the “small drawings” that prevent the big failures.
3. Sections and Details: Where the Truth Lives
Plans show location; details show constructability. Always trace a detail through:
- how it keeps water out,
- how loads transfer,
- how it can be inspected before it’s concealed.
4. RFIs: How to Ask the Question That Gets an Answer
Good RFIs reduce delay and rework. A useful RFI includes:
- the exact drawing reference and revision,
- a marked-up sketch/photo of the issue,
- two clear options (if possible) with a preferred recommendation,
- impact statement: cost/time/safety if not resolved.
5. Substitutions: The Dangerous “Equivalent”
Substitutions must consider strength, stiffness, durability, and connection compatibility. “Same depth” or “same thickness” is not equivalence.
6. Record-Keeping: Your Best Defence
- Keep transmittals, inspection photos, and signed checklists.
- Record any site changes and get written approval before proceeding.
- Capture concealed works before lining (tie-downs, bracing, fire-stopping where relevant).