Shop Drawing Checking Guide
Written by Allan – Jan 2002
Why is steel shop drawing checking important?
The “buck stops” at steel shop drawings. Steel shop drawings cannot be interpreted, as working drawings are. They are specialized, precise, instructions to the fabricator. Checking is therefore very important, as the entire building geometry is generally in the control of only one steel detailer. The Checker reduces the chance of individual error to a commercially acceptable level.
What qualifications does a checker need?
1. Experience in steel fabrication procedures
2. Strong geometry skills
3. Attention to detail
4. The checker does not need to be a draftsperson
Areas to pay close attention
1. Design compliance
2. Geometric Accuracy
Recommended checking approach
1. Check primary building datums first. This often requires the checker to create his own layout.
1.1 Bay spacing
1.3 Roof Pitch
The reason why it is important to check these things first, is that all other items fit in around these datums. If the primary datums are right there is little chance of a major mistake.
2. Check secondary building datums
2.1 Column, Rafter, Bracing member sizes
2.2 Bracing setout
2.3 Purlin member sizes and spacing
2.4 Bolt size
2.5 Plate size
Every number must be checked. Therefore it is advantageous to have a robust method of communicating the checkers thoughts back to the detailer. This can be achieved by using the “Drawing Markup Method”.
Drawing markup method
A neat, well marked up, drawing is an excellent way of communicating the checkers thoughts. Here is a recommended markup system.
1. If a checker agrees with a number, the number is highlighted in blue pencil
2. If a checker disagrees with a number or linework, it is marked up in red pen
3. If the checker has a comment to make, it is written in normal pencil
The advantage of this system is the checker does not forget what has been checked. Also the detailer will not be confused, with what has or has not been checked, and what is a comment or an important change.
The “Threefold Chord” checking process
Ultimately the Detailer has the responsibility for drawing integrity, yet this can result in one person having too great a degree of geometric responsibility. Here is a process that reduces the chance of individual person error.
1. The Checker marks up the drawings, as described above
2. Checker red marks the Detailer agrees with, are marked with yellow highlighter as they are edited in the drawing. Red marks the Detailer disagrees with are marked with orange highlighter
3. The completed drawing and the markups are returned to the Checker. Orange markups are discussed with the Detailer till a resolution is reached. Once this is finished, the Checker signs the final drawing. This drawing is now ready for construction issue.
This process has been proven, through experience, to be an excellent way of reducing errors to a commercially acceptable level.
Typical parts of a shop drawing set
1. Assembly drawings
2. Single parts
3. Purlin orders
4. Holding down bolt plan
5. General arrangement plan
6. End wall-building elevations
7. Field bolt list
8. Drawing index
All of these need to be checked
A Checker’s check list
1. Is all the information in the title block correct?
2. Are the details presented in an “easy to read” manner?
2.1 All necessary sections/views present and projected properly.
2.2 All necessary dimensions present.
2.3 Any ambiguous dimensions.
2.4 All necessary annotations present and legible.
2.5 Are details in accordance with standards, job specs, and fabricator policy?
2.6 Is their redundant or excessive information on the detail?
2.7 Could I build the piece from the information shown on the detail?
3. Did I check ALL the dimensions?
3.1 Are running dimensions required?
4. Did I check the member sizes?
4.1 If size is substituted did I consider impact on adjoining members?
5. Did I check the Connections?
5.1 For fit.
5.2 For engineers compliance
5.3 For code compliance
5.4 For erection clearance.
6. Did I read the specs?
6.1 Is the grade of the material noted correctly for all material?
6.2 site weld testing required?
6.3 Are there special cleaning and painting requirements?
6.4 Is shop inspection required: NDT, Radiograph, MagParticle etc?
6.5 Are weld procedures required?
6.6 Should any members or parts of members be noted “no paint”?
6.7 Is special testing required for the bolts?
6.8 Load indicator washers required?
6.9 Is shop assembly required?
6.10 Is Cambering required?
6.11 Is Punching dis-allowed or reaming required?
7. Is each shipping piece shippable? over length, over width, overweight.
8. Are all the quantities correct?
9. Does the bill of material match the dimensions on the drawing?
10. Are the erection drawings presented in an “easy to read” manner?
10.1 Are the marks in the proper location?
10.2 Do the columns have the correct direction orientation?
10.3 Is there a “North Arrow” on the plan?
10.4 Are all necessary dimensions shown correct on the plan / elevation views?
10.5 Are all member sizes shown correct for each member?
10.6 Is all field welding that is required shown correctly?
10.7 Are elevations at top of floors, roofs, landings etc. shown correct?
11. Are the bolts sizes, grades, and quantities correct?
11.1 Are oversize washers required for the holding down bolts?
11.2 Is there and special bolt requirements?
12. Did I thoroughly study all the design drawing to see if all the members in the in the scope of the fabricators contract have been detailed?
12.2 Deck support angles.
12.3 Embedded plates.
12.4 Ships ladders, trash gate frames, bollards, stairs, railings.
13. Is there a better, less expensive way to fabricate any of the pieces?
14. Are any pieces detailed beyond the capabilities of the fabricator’s equipment?
14.1 Are bend lengths and thickness within machine capacity?
14.2 Shop splices shown where required due to machine/material limitations?
14.3 Are punch sizes available for the slotted and round holes shown?
14.4 Are any pieces beyond lifting capacity of the shop?
15. Did I co-ordinate interface with other trades (holes for owner machinery, holes for wood, match holes in existing members)?
16. Did I put a lot of my unwanted opinion into marking up the detail (did I mark it up the way I would have detailed it) or did I check to see only if it was right or wrong (if it works let it go)?
17. Establish marks for typical parts such as base plates, cap plates, stiff plates, shear plates , connection angles.
18. Layout and confirm connections shown on design work… special concentration to brace bays, rafters or trusses or girders and parts connecting to them. (any component that is not straight or level
20. Layout and confirm connections for secondary items like girts, door frames and so on.
21. Layout and confirm connections for miscellaneous items stairs, handrail, ladders and so on.
22. What is the surface finishing?
22.1 Confirm no paint areas for field welding and slip critical connections
22.2 If galvanizing is involved confirm max sizes for shipping. Is there adequate drainage holes?