It is a classic scenario: your company implements a CRM with a standard five-stage sales funnel (e.g., Contact, Qualification, Proposal, Negotiation, Closing). Six months later, the funnel is abandoned. Salespeople manage their deals in parallel spreadsheets, and the CRM becomes an expensive graveyard of obsolete data. Why? Because the implemented funnel was pure fiction. It did not reflect the complex, non-linear reality of your company's sales process.
The fundamental mistake is treating the funnel as a pre-packaged mold. Every company, industry, and product has a unique buying process. Imposing a generic funnel is a futile attempt to force reality to adapt to a theoretical model. The real solution lies in building a funnel that expresses the reality of the field.
In this article, we present a methodology to build a sales funnel from scratch, based on Kurt Lewin's Field Theory. You will learn how to map your customer's "life space," identify the actual membranes and barriers in your process, and create a funnel that acts as an accurate map of your commercial battlefield.
The Problem with the Generic Funnel: A Critical Analysis
Generic funnels fail for three main reasons:
- False Linearity: They assume the customer moves linearly (A → B → C), when in reality the B2B buying process is chaotic, involving constant advances and retreats.
- Focus on the Seller, Not the Customer: The stages reflect the actions of the seller (such as "Proposal Sent") instead of focusing on the customer's decision and validation milestones (such as "Internal Consensus Reached").
- Lack of Clear Transition Criteria: Without objective rules for what must occur for a deal to move to the next stage, the funnel becomes purely subjective and invalidates reliable forecasting.
Kurt Lewin's Methodology to Map Reality
To build a functional funnel, we must understand the forces at play. Kurt Lewin's Field Theory offers us the conceptual framework. Instead of imposing artificial stages, we discover the natural membranes that already exist in your commercial process.
Step 1: Force Field Mapping (Interviews and Workshops)
The first step is to gather your top sales professionals for a qualitative workshop. The goal is to map the "life space" of a sales opportunity through targeted diagnostic questions:
- "Think of a deal you won. What were the crucial moments and turning points from the first contact to the closing?"
- "Think of a lost deal. Where exactly did it stall? What was the insurmountable barrier?"
- "What needs to happen for you to be sure a deal will close? What are the practical signs?"
- "What are the biggest objections or apprehensions our customers raise in each phase?"
The result of this mapping will be a clear set of driving forces (signals of progress) and restraining forces (barriers that stall the sale).
Step 2: Identifying the Membranes (Grouping Barriers)
With the barriers and turning points listed, group them by affinity. Each group of similar barriers represents a "membrane" that the customer must cross to advance in the buying journey. A sales funnel only has value if each stage represents a real, measurable increase in the probability of closing.
Example of Grouping for a B2B Software Company:
- Barriers: The customer does not understand the problem; thinks it is not a priority; has no defined budget.
- Membrane 1: Problem Awareness and Prioritization.
- Barriers: Doubts about technical alignment; need for validation with the engineering team; request for practical demonstrations.
- Membrane 2: Solution Validation.
- Barriers: Cost comparison with competitors; purchasing and financial approval bureaucracy; ROI validation.
- Membrane 3: Financial and Contractual Justification.
In this way, instead of a generic funnel, you discover the three real membranes of your process, which will define your commercial stages.
Building the Sales Funnel Based on Reality
With the membranes identified, we structure the funnel operationally in the CRM.
Step 3: Defining the Funnel Stages
The stages should directly reflect the mapped membranes:
- Qualification: The lead meets the basic requirements to enter the funnel.
- Diagnosis: Focus on crossing Membrane 1 (Problem Awareness).
- Solution: Focus on crossing Membrane 2 (Solution Validation).
- Negotiation: Focus on crossing Membrane 3 (Financial Justification).
- Closing: The outcome of the sale (Won or Lost).
Step 4: Defining the Transition Criteria
This is the most critical step. For each transition, determine concrete, objective, and verifiable actions that must occur for the deal to change phases. Configure the CRM to require these fields to be filled before allowing progress.
| Funnel Stage | Transition Criteria (Mandatory Requirements) |
|---|---|
| Qualification → Diagnosis | Lead meets minimum criteria (e.g., BANT/CHAMP) AND the diagnostic meeting is scheduled. |
| Diagnosis → Solution | Main pain point and financial impact identified AND the customer agreed to participate in a focused demonstration. |
| Solution → Negotiation | Demonstration successfully completed AND the internal champion validated the solution AND the customer requested a formal proposal. |
| Negotiation → Closing | Commercial proposal sent and reviewed with the customer AND verbal agreement on price/terms established AND contract sent for signature. |
Step 5: Attributing Probabilities
Analyze historical sales data to assign real statistical probabilities to each stage of the funnel, increasing the accuracy of forecasting.
| Funnel Stage | Probability of Closing |
|---|---|
| Qualification | 10% |
| Diagnosis | 25% |
| Solution | 50% |
| Negotiation | 75% |
Real Funnel Examples by Industry
Applying this method results in distinct structures based on the operational reality of each market:
1. Digital Marketing Agency
- Membranes: Understanding the business challenge, strategic alignment of the proposal, and budget approval.
- Stages: Qualification, Briefing, Strategic Presentation, Negotiation.
2. High-End Real Estate Developer
- Membranes: Establishing an emotional connection with the property, in-person site visit with high satisfaction, and financial/legal due diligence.
- Stages: Qualification, Portfolio Presentation, Property Visit, Proposal and Due Diligence.
3. Low-Cost SaaS (Self-Service)
- Membranes: Initial tool activation ("Aha!" moment), recurring engagement, and reaching free plan usage limits.
- Stages: Trial Started, Core Features Used, Limit Reached, Upgrade.
Conclusion: The Funnel as a Living Organism
Building a funnel based on Kurt Lewin's methodology is not a single event, but a continuous process of unfreezing, changing, and refreezing:
- Unfreezing: Critically questioning and analyzing the failures of the current commercial process in the initial workshop.
- Changing: Configuring the new stages and transition rules in the CRM.
- Refreezing: Continuously training the sales team and monitoring the new indicators to solidify operational discipline.
The ideal funnel is not a generic pattern copied from the market, but the faithful modeling of your commercial operation. By structuring your funnel based on real membranes and barriers, the CRM ceases to be a bureaucratic control panel and transforms into a strategic navigation map for high performance.
References
- Lewin, K. (1947). Frontiers in Group Dynamics. Human Relations.
- Salesforce. (2025). How to Create a Sales Funnel That Works. Available at: https://www.salesforce.com/br/sales/funnel/