Spring isolation curb specifications are proven in the submittal, and a reviewer looks for eight items before reading any of them: stamped curb assembly drawings, spring deflection calculations, isolation efficiency at the operating frequency, a weld map, material certifications, HVAC cut sheet coordination, a seismic/wind attachment calculation where required, and the mounting hardware spec.
A package has to be complete before it can come back “approved as noted” or “revise and resubmit,” and typical Section 01 33 00 submittal procedures return an incomplete submittal with requirements for completion rather than reviewing it. If the supplier is new to your vendor list, the five-day vendor-add ends with this package in review.
What does a complete spring isolation curb submittal contain?
| # | Item | What the reviewer checks | Reference |
|---|---|---|---|
| 1 | Stamped curb assembly drawings | Seal, sheet set, revision status | AIA A201-2017 §3.12 |
| 2 | Spring deflection calculations | Load at each mount, deflection selected | ASHRAE Handbook: HVAC Applications |
| 3 | Isolation efficiency at operating frequency | Efficiency at the lowest operating speed | ASHRAE Handbook: HVAC Applications |
| 4 | Weld map | Every weld located and tied to a code | AWS D1.3/D1.3M:2025 |
| 5 | Material certifications | Mill certs matching the drawing callout | ASTM A653 |
| 6 | HVAC cut sheet coordination | Model, revision, footprint, weight, center of gravity | Unit manufacturer’s cut sheet |
| 7 | Seismic/wind attachment calculation | Restraint forces, where the project requires them | ASCE 7-22 |
| 8 | Mounting hardware spec | Isolator model, rated load, restraint | Project specification |
The curb drawing is one item on this list; our roof curb DWG guide covers what belongs inside it.
What do the stamped drawings have to show?
For a spring isolation curb, the stamped set covers three things: curb assembly, spring placement, and attachment to the structure. Check which stamp the spec calls for. A fabricator’s stamped detail carries a revision block and drawing number; a PE seal is different. When the contract documents require design services or certifications from the contractor, AIA A201-2017 §3.12.10.1 requires the licensed design professional’s signature and seal on the drawings, calculations, and shop drawings they prepare.
Check the seal against the jurisdiction, too. New York’s licensing authority, for example, expects delegated shop drawings to be signed and certified by a New York licensee.
On a resubmittal, look for revision clouds. AIA A201-2017 §3.12.9 requires the contractor to call out, in writing or on the resubmitted drawings, any revision beyond those the reviewer requested.
Which material and weld records belong in the package?
The weld map and mill certs connect the curb on the truck to the curb on the drawing. The weld map should cite AWS D1.3/D1.3M:2025, the current edition of the sheet steel welding code, which has separate clauses for welder qualification and inspection. Mill certs should match the gauge and coating designation called out on the drawing. Which material belongs on a data center roof is covered in our galvanized vs. aluminum comparison.
What should the calculations prove?
A reviewer checks that each calculation names its inputs: the unit model and cut-sheet revision, the load at each mount, the deflection selected, and isolation efficiency at the lowest operating speed. The method behind those numbers is in our spring deflection sizing guide.
Item 7 applies where ASCE 7-22 Chapter 13 governs the project; FEMA E-74 notes that isolators tend to amplify seismic response unless restrained. For item 8, the mount interfaces to verify are listed in our spring mount guide.
How does the package coordinate with the HVAC cut sheet?
Items 2, 3, and 7 all draw their numbers from the cut sheet: footprint, operating weight, and center of gravity. So the first check on a data center package is simple: every calculation should cite the same cut-sheet revision as the drawings. When the unit selection changes after approval, the affected items go back through review.
Custom Curb never installs product, yet makes installation drawings available to customers, including GCs buying its spring isolation curb packages. The crew setting the curb needs more than a reviewer’s markup.
What does the GC owe the package before it reaches the engineer?
Under AIA A201-2017 §3.12.5, the contractor reviews the package for compliance with the contract documents, approves it, and only then submits it. Communications with suppliers run through the contractor under §4.2.4, so a curb package belongs on the GC’s desk before it reaches the engineer’s.
That review carries weight. Under §4.2.7, the architect’s review does not relieve the contractor of its §3.12 obligations, and under §3.12.8, approval does not excuse a deviation the contractor failed to flag in writing at submission. If the package proposes a different isolator, deflection, or restraint than the spec, say so on the transmittal.
Schedule follows from the same section: §3.12.7 bars any work that requires a submittal until that submittal is approved. On a fast-track data center build, a curb package that clears review on the first pass is fabrication time the schedule keeps.
Frequently Asked Questions
Does every spring isolation curb submittal need a PE seal?
Only when the contract documents delegate design or certification to the contractor; AIA A201-2017 §3.12.10.1 then puts that professional’s seal on the drawings and calculations.
Is a fabricator’s stamped detail the same as a PE-sealed drawing?
No. A fabricator’s stamp identifies the drawing and its revision. A PE seal is a licensed professional’s signature, required where the contract delegates design.
Can the curb supplier send the submittal straight to the engineer?
Usually not. Under AIA A201-2017 §4.2.4, supplier communications run through the contractor, and §3.12.5 puts the contractor’s approval first.
Is a seismic attachment calculation always required?
No. It depends on ASCE 7-22 Chapter 13 and the contract documents.
What happens if the HVAC unit changes after approval?
The calculations change with it, and the resubmittal must call out every revision under AIA A201-2017 §3.12.9.