How to Send Bid Invitations to Subcontractors — A GC's Step-by-Step ITB Guide
Sending bid invitations to subcontractors involves five steps: (1) build the sub list from your prequalified database, organized by trade; (2) prepare the invitation to bid (ITB) package with scope matrix, drawings, specifications, and bid requirements; (3) distribute via email, BuildingConnected, or your bid management platform; (4) follow up to confirm receipt and intent to bid; and (5) manage addenda and deadline communication through the same channel. Aim for 3–5 qualified responses per trade; invite 5–8 subs per trade to account for non-response.
Sub bid coverage determines the GC's bid competitiveness. A trade with only one responsive sub yields no price competition and no backup option. A trade with 5 qualified proposals gives the estimator genuine options — and the bid leveling process that follows can identify the best overall value, not just the least expensive exclusion.
The invitation to bid (ITB) is the mechanism by which the GC solicits those proposals. Done well, it gets qualified subs engaged and produces complete, comparable proposals. Done poorly, it yields thin coverage, incomplete proposals, and scope gaps that emerge at buyout.
This guide covers the full ITB process — from building the sub list through managing the deadline.
STEP 1: BUILD THE SUB LIST BY TRADE
The starting point is your prequalified subcontractor database. For each trade package, pull the list of approved subs with coverage in the project's geographic market and relevant project type experience.
How many subs to invite per trade:
- Target 3–5 responsive proposals (this gives genuine price competition and backup options)
- Invite 5–8 subs per trade, accounting for the fact that 30–50% of invitations typically don't result in a proposal
- For large-value trades (MEP, structural steel, exterior wall), invite more — 6–10 — because coverage gaps on high-cost trades are the most dangerous
Factors that affect how many subs to invite:
- Market conditions: In tight markets where subs are busy, response rates drop. Invite more.
- Project type: Specialized scopes (fire suppression, elevator, process piping) have fewer qualified subs. Invite all of them.
- Project location: Out-of-market projects have thinner sub coverage. Cast the net wider.
For sub list sources: What Is Subcontractor Prequalification?
STEP 2: PREPARE THE ITB PACKAGE
The ITB package is the package of information a sub needs to price their scope accurately. An incomplete or unclear ITB produces incomplete proposals — scope gaps that come back as change orders.
Essential components of an ITB package:
Cover Letter / Invitation Email
- Project name, address, and brief description
- Invitation status (is the GC bidding this project or already awarded?)
- Bid deadline — date and time
- Submission format (email, portal, fax)
- GC contact for questions
- Any pre-bid meeting or job walk information
Scope of Work / Scope Matrix
The most important document in the ITB. The scope matrix defines exactly what the invited sub is responsible for — no more, no less. It lists: included scope items, interface responsibilities with adjacent trades, items that are explicitly excluded from this sub's scope (and who is responsible for them), allowances if applicable, and any alternates the sub should price separately.
A well-written scope matrix prevents the two most common bid leveling problems: subs including scope they shouldn't (over-pricing) and subs excluding scope they should include (under-pricing that surfaces at buyout). How to Write a Construction Scope of Work
Project Drawings
The drawings relevant to the invited trade. For a concrete sub, include structural drawings, architectural foundation plans, and civil grading plans. Don't send the full drawing set to every sub — it creates confusion and large file sizes. Include only the sheets relevant to their scope, plus Division 01 (General Requirements).
Project Specifications
The specification sections relevant to the invited scope. Include Division 01 General Requirements (these apply to all subs) plus the specific trade sections. For a mechanical contractor, include Division 23 plus any Division 01 sections covering temporary facilities, construction schedule requirements, and submittals.
Subcontract Form
If the project requires a specific subcontract form (AIA A401, or a GC proprietary form), include it in the ITB so subs can review the contract terms before bidding. Subs who see onerous contract terms for the first time after bidding either reprice or withdraw — neither outcome is efficient.
Bid Form (optional but recommended)
A structured bid form ensures subs provide their pricing in a consistent format — making comparison easier. Include: base bid, alternates (if any), unit prices (if applicable), and a section for exclusions and clarifications.
STEP 3: DISTRIBUTE THE INVITATION
Distribution channels:
Email: Simple, direct, and still widely used. Use a standard email template with the ITB package attached or linked via file-sharing service (Dropbox, Google Drive, Procore drawings). Keep the email to the point; subs receive many ITBs.
BuildingConnected: The most widely adopted platform for ITB distribution. Upload the package once; the system manages distribution, tracks who has opened the invite, and collects proposals through the platform. Sub coverage is broad because most subs are already active on BC.
SmartBid or similar bid management platform: Similar function to BuildingConnected with Procore integration.
Best Bid Management Software
Distribution timing:
- Issue the ITB as early as possible. A 2–3 week bidding period is minimum for most commercial scopes. Complex scopes (full MEP, curtain wall) need 3–4 weeks.
- For a project with a 4-week bid period, issue ITBs by day 1; don't wait until week 2 when the sub's capacity to prepare a competitive proposal is reduced.
STEP 4: FOLLOW UP AND CONFIRM INTENT
Distributing the ITB is not enough. Follow up is essential, particularly in tight markets or when sub coverage is critical.
First follow-up (2–3 days after distribution):
- Confirm receipt of the ITB package
- Ask for a preliminary intent to bid (yes / no / possibly)
- For no/possibly responses, understand why — is it capacity, project type, location, or contract terms? Sometimes a brief clarification conversation turns a possible into a yes.
Mid-bid follow-up (1–1.5 weeks before deadline):
- Check in on progress; answer any questions
- Remind of the deadline
- For subs you haven't heard from, one more confirmation attempt
Day-before follow-up:
- For critical trades where coverage is thin, call the subs directly to confirm they are submitting
Document all follow-up: Note in your bid log which subs confirmed intent, which declined, and which are undecided. This creates a coverage picture going into deadline day and lets you escalate coverage outreach early if a key trade looks thin.
STEP 5: MANAGE ADDENDA AND CHANGE COMMUNICATION
During the bidding period, the owner or design team may issue addenda — revisions to the drawings, specifications, or bidding requirements. All addenda must be distributed to all invited subs through the same channel as the original ITB.
Addenda management best practices:
- Confirm receipt of each addendum from each sub (particularly on large multi-trade bids)
- If an addendum significantly changes the scope, consider extending the bid deadline
- Require subs to acknowledge the addenda number(s) in their proposals
- On bid day, check that received proposals reference the correct addenda
FREQUENTLY ASKED QUESTIONS
How many subcontractors should I invite per trade?
Invite enough to expect 3–5 responses — typically 5–8 per trade, more for specialty scopes with few qualified contractors in the market. Having fewer than 3 responsive proposals per trade reduces price competition and leaves the GC exposed if the selected sub withdraws.
What should I do if subs aren't responding to my ITBs?
Low response rates usually indicate one of three problems: (1) the sub is too busy — you need more subs in your database for that trade; (2) the project doesn't fit their scope or location — review whether you're inviting the right sub types; (3) the ITB package is too complex or unclear — simplify the scope matrix and reduce file size. For persistent coverage gaps, cold outreach to new subs and referrals from other GCs can expand your sub network.
Is it acceptable to invite subs to a bid you're not sure you'll win?
Yes — inviting subs to a bid before the GC is awarded is standard practice on hard bid projects. The professional norm is to inform invited subs promptly if the GC does not win the bid (or decides not to bid), and to follow up with subs who submitted proposals to thank them for their time.
CONCLUSION
A well-executed ITB process is the foundation of competitive bid coverage. The subs who respond to clear, professional ITBs with complete scope matrices are the subs who produce comparable, complete proposals — and those proposals are the raw material for accurate bid leveling and sound award decisions.
The time invested in a complete ITB package pays back in fewer scope clarification calls, fewer bid discrepancies, and fewer scope gaps at buyout.
REFERENCES
1. Procore. "Construction Procurement: A Guide to Purchasing & Logistics." https://www.procore.com/library/construction-procurement
2. DownToBid. "Subcontractor Bid Invitation Best Practices." https://downtobid.com/blog/subcontractor-prequalification-questionnaire
3. BuildingConnected (Autodesk). https://construction.autodesk.com/products/buildingconnected/
4. ConstructConnect. "The 7 Best Construction Bid Platforms in 2026." https://www.construction.com/the-7-best-construction-bid-platforms-in-2026/
5. Constrafor. "The Ultimate Guide to Subcontractor Prequalification for General Contractors." https://www.constrafor.com/the-build-up/the-ultimate-guide-to-subcontractor-prequalification-for-general-contractors