The Three-Part Spec Section: General, Products, Execution

Why this matters

A crew can install a duct system exactly as drawn, with every product the spec allows, and still owe the job a day of rework because of one paragraph it never saw. That paragraph almost always lives in Part 3 of the specification section, the part that says what has to happen on site: what to examine before starting, what to test and when, what to clean, what to hand over. Parts 1 and 2 get read in the office because they drive the order and the submittal. Part 3 is written for the field and is the part least likely to reach it.

The shape every section shares

Most commercial specifications follow CSI's SectionFormat, which divides each section into the same three parts in the same order. Once you know the order, any section in any division reads the same way. Here is the outline of one HVAC section, the kind of thing an HVAC shop meets on its first commercial ductwork job:

SECTION 23 31 13 - METAL DUCTS
PART 1 - GENERAL
 1.1 SUMMARY; RELATED SECTIONS: 23 05 93 TAB,
     23 07 13 DUCT INSULATION, 07 84 00 FIRESTOPPING
 1.2 REFERENCES: SMACNA DUCT CONSTRUCTION STANDARDS
 1.3 ACTION SUBMITTALS: PRODUCT DATA, SHOP DRAWINGS
 1.4 INFORMATIONAL SUBMITTALS: LEAKAGE TEST REPORTS
 1.5 QUALITY ASSURANCE: INSTALLER QUALIFICATIONS
 1.6 WARRANTY
PART 2 - PRODUCTS
 2.1 MATERIALS: GALVANIZED SHEET, ASTM A653, G90
 2.2 PERFORMANCE: PRESSURE, SEAL AND LEAKAGE CLASS
 2.3 SEALANTS, HANGERS AND SUPPORTS
PART 3 - EXECUTION
 3.1 EXAMINATION
 3.2 INSTALLATION: PER SMACNA; CAP OPEN ENDS
 3.3 FIELD QUALITY CONTROL: LEAKAGE TEST BEFORE
     INSULATION, 25 PCT OF 2 IN. W.G. CLASS DUCT
 3.4 CLEANING
 3.5 PROTECTION: KEEP ENDS CAPPED TO TURNOVER

Article numbers and exact headings vary between firms. The three parts and what goes in each do not.

Part 1, General: what you owe on paper

Part 1 is the section's administrative half. Read it for four things.

Related sections. The list of other sections this one touches. It is the map to work that is yours but filed elsewhere: here, the testing and balancing section that will measure your system, the insulation section that must not start until your test passes, and the firestopping section that governs your penetrations (see related: The MasterFormat Divisions a Service Trade Lives In).

References. The standards incorporated by name. A reference makes the whole standard part of the contract to the extent the section invokes it, so "construct per SMACNA" pulls in a very large book of gauges, joints, reinforcement and hanger spacing. The section should name an edition; if it does not, Division 01 usually says which edition applies.

Submittals, sorted by kind. Many sections split them three ways. Action submittals (product data, shop drawings, samples) need the designer's review before you fabricate or order. Informational submittals (test reports, certificates, qualifications) are for the record and usually are not stamped. Closeout submittals (manuals, warranties, record drawings) are due at the end. Each kind runs through the procedures in Division 01 (see related: What a Submittal Is and Why It Comes Before the Work).

Quality assurance and warranty. Installer qualifications, mock-ups, preinstallation meetings, and any warranty longer than the standard one-year correction period. A special warranty in Part 1 is an obligation you price; a qualification requirement is one you may or may not meet.

Part 2, Products: what you may buy

Part 2 says what goes into the work: manufacturers, materials, performance and fabrication. In the outline above it fixes galvanized sheet to ASTM A653 with a G90 zinc coating, and it fixes the duct's pressure class, seal class and leakage class, which decide joint construction and sealing.

How the section names products, whether as one proprietary product, a basis of design with listed equals, a reference standard or a performance result, changes what you are allowed to substitute and what you become responsible for (see related: Basis of Design, Proprietary and Performance Specifications). Part 2 can also carry source quality control, meaning tests performed at the factory before shipment, which you document rather than perform.

Part 3, Execution: what you must do on site

Part 3 is the field's half, and its articles tend to run in the order the work does:

• Examination: inspect the conditions you are installing into before you start, and report anything unacceptable. Many sections say that starting work means you accepted the conditions, which turns a skipped look into an owned problem.
• Preparation and installation: the methods, sequence and tolerances. Small sentences here carry real cost, such as "cap open ends of ductwork during construction," which keeps construction dust out of a system the owner will breathe through.
• Field quality control: the tests and inspections, when they happen in the sequence, who witnesses them, and what passes. This is the article most often missed, and the costliest to miss, because tests are sequenced against other trades' work.
• Adjusting, cleaning and protection: what condition the work must be in at turnover.
• Startup and demonstration: start-up, training, and the field records they produce. The closeout documents themselves are usually listed in Part 1 and handed over through Division 01.

Why Part 3 is the one crews skip

Not carelessness; logistics. The project manual lives in the office. The estimator reads Part 2 to price materials, the project manager reads Part 1 to build the submittal log, and the crew gets drawings, an approved submittal and a start date. Nothing in that flow puts Part 3 in a foreman's hands, and the drawings rarely repeat it. So the paragraphs written specifically for the people doing the work are the ones the people doing the work never read.

Worked example: the leakage test nobody scheduled

The section above requires testing 25 percent of the 2 in. water gauge (w.g.) pressure-class duct before insulation, at the section's stated leakage class of CL 6 and a test pressure of 2 in. w.g. The job has 160 linear ft of 24 x 12 in rectangular main in that pressure class.

Size the test section. 25 percent of 160 ft is 40 ft. The duct's perimeter is 2 times (24 plus 12), which is 72 in, or 6 ft. Surface area is 6 ft times 40 ft, which is 240 sq ft.

Compute the allowable leakage. SMACNA's leakage relationship gives allowable leakage F, in cfm per 100 sq ft of duct surface, as the leakage class times the test pressure raised to the 0.65 power, with pressure in inches of water. At the section's own values:

• 2 raised to the 0.65 power is about 1.569.
• F = 6 times 1.569, about 9.41 cfm per 100 sq ft.
• Allowable for the test section = 9.41 times (240 divided by 100) = 9.41 times 2.40, about 22.6 cfm.

Check it the other way: 22.6 cfm across 240 sq ft is 0.094 cfm per sq ft, which is 9.4 per 100. The numbers close.

What happened. The foreman never saw 3.3. The crew hung and sealed the main, the insulation sub followed the next morning, and the 40 ft section was wrapped before anyone looked for a test. When the TAB contractor asked for the leakage report the section listed as an informational submittal, there was none. The section had said before insulation, so the duct wrap came off 40 ft of main: by the crew's own estimate, most of a day for two people to strip, test, re-seal and have the insulation reinstalled, plus the insulation sub's return trip.

The test itself. The first run measured 31 cfm against an allowable of 22.6, a failure. Leak-finding smoke drifting out of duct joints is exactly what a building's smoke detectors exist to catch, so before using it the crew had the alarm contractor and the building contact put the affected zone on test, with whatever fire watch the owner's impairment procedure required, and restored it when the smoke was clear. Leaks were found at two transverse joints whose sealant had skipped the corners. After re-sealing, the retest measured 18 cfm, under 22.6, and passed. Had the test run before insulation as written, finding and fixing those two joints would have cost an hour and nothing else.

What would have changed it. Had the section said test after insulation, or left the sequence open, the crew's order of work would have been fine and only the test would have been owed. Had it required 100 percent testing, the test effort roughly quadruples, which is exactly the sort of thing that has to reach the estimate, not the foreman's surprise list.

What a section does not tell you

A spec section is deliberately narrow, and reading it as if it were the whole contract produces its own errors. It does not carry quantities or locations; those are on the drawings, and the two are read together (see related: When Drawings and Specs Disagree: The Order of Precedence). It does not repeat the procedures for submittals, substitutions or closeout; it points to Division 01, and the pointer carries the full rule. And it usually does not settle who furnishes and who installs an item that crosses trades, such as a unit disconnect or a duct smoke detector; that split is in the common-work sections or a responsibility matrix, and a section that is silent on it is a question for the RFI log, not permission to assume.

Getting Part 3 to the truck

The fix is a one-page field sheet per section, made by whoever reads the book: every Part 3 sentence that names a test, an inspection, a hold point, a sequence ("before insulation," "before concealment," "prior to backfill"), a witness, or a protection requirement, with the article number beside it. Two minutes of reading per section, and the hold points go on the schedule instead of the punch list. The same pass picks up Part 3 items owed at closeout, which the closeout package will ask for later (see related: How to Assemble a Closeout Package).

References

• CSI SectionFormat and MasterFormat, Construction Specifications Institute, in the editions the project manual follows.
• SMACNA HVAC Air Duct Leakage Test Manual and SMACNA HVAC Duct Construction Standards, in the editions the section names (leakage class and allowable leakage).
• See related: The MasterFormat Divisions a Service Trade Lives In
• See related: How to Prepare a Submittal for Your Own Scope; The Submittal Log SOP
• See related: Basis of Design, Proprietary and Performance Specifications