What Is the QFD House of Quality and How Do You Build One?

Quality Function Deployment (QFD) is a structured method for translating customer requirements into specific engineering characteristics and production controls. Developed by Yoji Akao in Japan in the late 1960s and formalized in the 1970s, QFD is often visualized through its central tool: the House of Quality. This article explains what the House of Quality is, how it works, and how you can apply it to align your product design with what customers truly value.

What It Is

The House of Quality is a matrix-based diagram that connects "what" the customer wants (customer needs) to "how" the product or service can be delivered (engineering characteristics). It is called a "house" because the matrix is shaped like one: the left "wall" lists customer requirements, the ceiling lists engineering characteristics, the main body shows the relationship between them, and the "roof" displays correlations among the engineering characteristics themselves.

The method is part of the broader QFD approach, which uses a waterfall matrix to cascade customer needs through four phases: product planning, parts deployment, process planning, and production planning. The House of Quality is the first and most widely used of these matrices, serving as the foundation for all downstream decisions.

How It Works / Steps

Building a House of Quality involves the following steps:

1. Identify customer requirements (Whats). Collect and prioritize customer needs, often through surveys, interviews, or focus groups. Assign an importance weight to each need (e.g., on a 1–5 scale, where 5 is most important).

1. Define engineering characteristics (Hows). Translate each customer need into measurable technical requirements. These are the design parameters that your team can control and improve.

1. Construct the relationship matrix. In the main body of the house, assess how strongly each engineering characteristic affects each customer need. Use symbols or scores: typically, 9 = strong relationship, 3 = moderate, 1 = weak, and blank = no relationship.

1. Add the roof (correlation matrix). Evaluate how engineering characteristics interact with one another. Positive correlations indicate that improving one helps another; negative correlations indicate trade-offs.

1. Compute importance ratings. For each engineering characteristic, calculate a weighted importance score by summing the product of each customer need's importance weight and its relationship score with that characteristic.

1. Set targets. Based on the importance ratings, competitive benchmarking, and technical feasibility, set target values for each engineering characteristic.

A Worked Illustrative Example

Example data (illustrative only): Suppose you are designing a coffee mug.

• Customer needs (with importance weights on a 1–5 scale):

- Keeps drink hot (weight = 5)
- Easy to hold (weight = 4)
- No leakage (weight = 3)

• Engineering characteristics:

- Wall insulation (R-value)
- Handle ergonomics (grip angle)
- Lid seal strength (N)

• Relationship matrix (9 = strong, 3 = moderate, 1 = weak):

Customer Need (weight) | Wall Insulation | Handle Ergonomics | Lid Seal Strength

• Keeps hot (5) | 9 | 1 | 3
• Easy to hold (4) | 1 | 9 | 1
• No leakage (3) | 3 | 1 | 9

• Importance ratings:

- Wall Insulation: (5×9) + (4×1) + (3×3) = 45 + 4 + 9 = 58
- Handle Ergonomics: (5×1) + (4×9) + (3×1) = 5 + 36 + 3 = 44
- Lid Seal Strength: (5×3) + (4×1) + (3×9) = 15 + 4 + 27 = 46

Here, wall insulation has the highest importance rating, so your team should prioritize improving it while balancing trade-offs with handle ergonomics (e.g., a thicker wall may make the handle less comfortable).

Common Pitfalls

• Skipping customer validation. If the importance weights are guessed rather than based on real customer data, the entire matrix loses credibility.
• Too many details. Overloading the house with dozens of needs and characteristics makes it unreadable. Keep it focused on the most critical items.
• Ignoring the roof. Negative correlations reveal genuine trade-offs; overlooking them leads to unrealistic targets.
• Treating it as a one-time exercise. The House of Quality should be revisited as customer needs evolve or new technical solutions emerge.

Start Building Your House of Quality

The House of Quality is a practical, visual way to ensure your engineering decisions are driven by customer priorities, not internal assumptions. To get started quickly, you can use the free, structured template available at https://www.6sq.com/tools/qfd/, which walks you through the matrix step by step.