Key points
- Delivery method decides who carries design risk, how early a mechanical contractor is involved, and how price is set: bid-build, design-build, CM-at-risk, design-assist, and negotiated work all behave differently.
- A competitive mechanical bid is built from a takeoff of the plans and specs, equipment quotes, labor, rigging, permits, general conditions, and risk allowances. Clarifications and exclusions matter as much as the number.
- Public work adds bonding, subcontractor listing, DIR registration, and prevailing wage requirements in California.
- Submittals, RFIs, coordination, testing and balancing, and commissioning take real time and should be in the schedule from day one.
- Closeout documents (as-builts, O&M manuals, startup reports, warranties) are a deliverable. Final payment often depends on them.
Delivery methods and what they mean for the mechanical contractor
| Method | How it works | Mechanical contractor's role | Best when |
|---|---|---|---|
| Design-bid-build | Owner hires a designer, completes plans and specs, then bids to contractors | Bids a defined scope against the documents | Scope is clear; public agencies requiring low bid |
| Design-build | One entity is responsible for both design and construction | Often a design-build partner or sub with design-assist input | Speed matters; owner wants one point of responsibility |
| CM at risk / GMP | Construction manager joins during design and guarantees a maximum price | Provides early pricing, constructability, and value engineering | Complex projects with evolving scope |
| Design-assist | Mechanical sub helps the engineer develop details and pricing during design | Contributes systems selection, coordination, cost input | Complex mechanical systems, tight schedules |
| Negotiated / sole source | Owner selects a contractor based on qualifications and negotiates price | Prices openly, often with transparent markups | Ongoing relationships, emergencies, small to mid-size scope |
| Job order contracting (JOC) / on-call | Pre-priced unit price book or term contract for repetitive work | Executes task orders at contracted pricing | Public agencies with continuous small projects |
What's in a mechanical bid package
- Drawings (M-series): Equipment schedules, plans, sections, details, controls diagrams, and riser diagrams.
- Specifications: Division 23 (HVAC) in the CSI MasterFormat, plus related sections for plumbing (22), electrical (26), controls (23 09 00), testing and balancing (23 05 93), and commissioning (01 91 00).
- General and supplementary conditions: Insurance, bonding, schedule, liquidated damages, change-order process, and payment terms.
- Addenda: Changes issued during the bid period that must be acknowledged. Missing one can disqualify a bid.
- Bid forms: Lump sum, alternates, unit prices, subcontractor listing in public work.
- Site walk and RFIs: Pre-bid walks are often mandatory on public projects.
How a competitive mechanical estimate is built
- Document review and scope split. Identify what is in and out of the mechanical scope, including controls, electrical connections, roofing work, and fire-smoke dampers.
- Takeoff. Quantify equipment, ductwork, piping, insulation, controls devices, and accessories from the drawings.
- Vendor quotes. Equipment pricing and lead times from manufacturers and reps; controls, TAB, insulation, and specialty subs.
- Labor. Man-hours by task and the correct wage rates (prevailing wage or union scale when applicable).
- Equipment and logistics. Cranes, rigging, hoists, scaffolding, temporary cooling.
- Permits, fees, bonds, insurance, and general conditions.
- Risk and escalation. Allowances for price volatility, long-lead items, and unknowns.
- Overhead and profit. Applied transparently.
- Clarifications and exclusions. The place to state assumptions so the bid is comparable and defensible.
Reading bids side by side
A low number with a long exclusions list is not a low bid. Compare scope, alternates, equipment makes and models, schedule, and what is carried for controls, TAB, and commissioning.
Bonds and public-work rules
- Bid bond (often 10% of bid) guarantees the bidder will sign the contract if awarded.
- Performance and payment bonds (commonly 100% of contract value) protect the owner and the subs and suppliers on public jobs.
- Subcontractor listing: California's Subletting and Subcontracting Fair Practices Act requires prime bidders on public projects to list subcontractors performing more than a small fraction (one-half of one percent) of the bid.
- Contractor registration and prevailing wage: See the prevailing wage guide.
- Retention: Owners hold back a percentage of each progress payment until completion; California public works limit retention to 5% in most cases, while private contracts vary.
- Bid protests and responsiveness: Public owners award to the lowest responsive, responsible bidder; errors on forms can disqualify.
For a public-agency view of procurement, see public agency and school HVAC procurement.
From award to closeout
| Phase | What happens | Common friction |
|---|---|---|
| Submittals | Equipment data, shop drawings, and control diagrams go to the engineer for review | Slow reviews, substitutions, lead-time surprises |
| RFIs and coordination | Questions on conflicts with structure, electrical, fire protection, ceilings | Late discovery of clashes; BIM coordination mitigates |
| Procurement | Equipment ordered and scheduled | Long-lead items (large RTUs, chillers, switchgear) drive the schedule |
| Installation | Rigging, curbs, ductwork, piping, controls, electrical connections | Access, sequencing with other trades, inspections |
| Startup, TAB, commissioning | Equipment started; airflow and water flows balanced; systems tested against design intent | Controls not ready, incomplete punch lists |
| Closeout | As-builts, O&M manuals, training, warranties, final payment | Missing documents delay final payment |
Closeout documents owners should require
- As-built drawings showing actual installed locations and changes.
- Operation and maintenance manuals with parts lists and maintenance schedules.
- Startup reports and test results (pressure tests, electrical, refrigerant).
- TAB (test and balance) report.
- Controls sequences, point lists, and passwords/handover.
- Warranty certificates with start dates and terms.
- Training records for facility staff.
- Permit sign-offs and energy-code certificates.
We load asset data into the DaVinci Portal at closeout so your maintenance team inherits equipment histories from day one.
Choosing the right path for your project
- Fixed scope, public agency: design-bid-build with complete documents.
- Complex, fast-track, or occupied building: involve a mechanical contractor early (CM at risk, design-assist, or design-build).
- Portfolio of repeat projects: negotiated, term, or JOC contracts that preserve relationships and speed.
- Emergency: negotiated with documented unit prices to keep control without losing time.
Frequently asked questions
Do you bid on projects outside Orange County?
Yes. We pursue larger commercial and public mechanical projects, including out-of-state work, on a project-by-project basis. See our bid-projects page.
What size projects do you take?
From single-unit replacements to multi-unit and central plant scopes. Contact us with the plans or scope and we will confirm fit.
Can you help during design?
Yes. Early input on equipment selection, constructability, and budget helps projects avoid redesign and bid surprises.
What do you need to give a firm price?
Plans and specs, or a site walk and equipment list for smaller scopes. Clear access, schedule, and any prevailing wage or PLA requirements.
Talk to a commercial tech
Have a site this applies to?
Davinci Mechanical is the commercial and union division of Scottish Tom's Heating & Air. Send us the equipment list or the problem and we'll tell you what we'd check first.