The House of Quality (HOQ) is a matrix-based planning tool that translates customer requirements into prioritized, measurable technical design requirements. It’s the central tool of Quality Function Deployment (QFD), and it gets its name from its shape: customer needs on the left, design requirements across the top, a relationship matrix in the center connecting them, and a triangular “roof” on top showing how the design requirements interact with each other, together forming the outline of a house.
In practice, a team rates how important each customer need is, scores how strongly each design requirement relates to each need using a standard weighting (usually 9 for strong, 3 for medium, 1 for weak), and multiplies those numbers to calculate which design requirements deserve the most investment.
The House of Quality is the first of four cascading QFD phases; the process ultimately flows down into the same Control Plan a Six Sigma team builds to sustain a process.
Quick Reference Table
| Element | What It Means | Where It Sits in the “House” |
| Customer Requirements (“Whats”) | The customer needs, in their own words, with importance ratings | Left wall/room |
| Design Requirements (“Hows”) | The technical characteristics the team can actually control | Roof beams / top row |
| Relationship Matrix | Scores how strongly each design requirement affects each customer need | The main body/floor of the house |
| Correlation Matrix (Roof) | Shows how design requirements help or conflict with each other | The triangular roof |
| Competitive Assessment | How the product compares to competitors on each customer need | Right wall/room |
| Technical Priorities | The calculated, prioritized ranking of design requirements | Basement/foundation |
Table of contents
Key Takeaways
- The House of Quality is named for its shape, not just a metaphor. Customer needs, design requirements, a central relationship matrix, and a triangular correlation “roof” on top together form the outline of a house.
- The House of Quality and QFD are not the same thing. QFD is the overall methodology; the House of Quality is its first, best-known matrix.
- The relationship matrix uses a standard numeric weighting, typically 9 for a strong relationship, 3 for medium, and 1 for weak (sometimes shown as a filled circle, open circle, and triangle).
- Technical importance is calculated by multiplying, not just estimating. Each design requirement’s priority score comes from multiplying customer importance by relationship strength, then summing across all customer needs.
- QFD was developed in Japan in 1966 by Yoji Akao, and first demonstrated at Mitsubishi Heavy Industries’ Kobe Shipyard around 1972, before spreading to Toyota and later to Ford and Xerox in the United States during the 1980s.
- The House of Quality is only the first of four QFD phases. A full QFD deployment cascades customer priorities down through Parts Deployment, Process Planning, and finally into Production Planning, the same territory a Six Sigma Control Plan occupies.
- There is no single, universally standardized version of the House of Quality. Real-world versions vary in which “rooms” they include, though the core structure (customer needs, design requirements, relationship matrix, and roof) shows up consistently.
What Is a House of Quality?
The House of Quality (HOQ) is a structured matrix that translates the Voice of the Customer into specific, measurable technical design requirements, and prioritizes those requirements based on how much they actually matter to the customer. It’s the signature tool of Quality Function Deployment (QFD), a broader methodology for making sure a product or process is designed around what customers actually asked for, rather than internal assumptions about what they might want.
At its core, the House of Quality answers a deceptively simple question: given everything customers say they want, which specific technical characteristics should the team actually prioritize, and by how much?
Public, Onsite, Virtual, and Online Six Sigma Certification Training!
- We are accredited by the IASSC.
- Live Public Training at 52 Sites.
- Live Virtual Training.
- Onsite Training (at your organization).
- Interactive Online (self-paced) training,
Why Is It Called a “House” of Quality?
This is the detail most competing content, including the previous version of this page, skips entirely, and it’s genuinely useful for understanding how the tool is laid out. The House of Quality earns its name because its finished matrix visually resembles the outline of a house:
- The left wall holds customer requirements and their importance ratings.
- The top row (like ceiling beams) holds the technical design requirements.
- The main body of the house is the relationship matrix, showing how strongly each design requirement connects to each customer need.
- The triangular roof, sitting on top of the design requirements, is the correlation matrix, showing where design requirements support or conflict with each other.
- The right wall often holds a competitive assessment, comparing performance against competitors on each customer need.
- The basement or foundation holds the calculated technical priorities, the actual output the rest of the process was built to produce.
Different real-world versions of the House of Quality vary somewhat in exactly which of these “rooms” they include, since there’s no single universally standardized template. But the core shape, customer needs, design requirements, a relationship matrix connecting them, and a correlation roof on top, shows up consistently enough that the house metaphor holds across nearly every version in practical use.
Also Read: What Are Data Quality Dimensions? The 6 Core Dimensions Explained
House of Quality vs. QFD: What’s the Difference?
This is a common point of confusion the existing page never addresses directly.
| Term | What It Is |
| QFD (Quality Function Deployment) | The overall methodology for translating customer needs into product, process, and production decisions |
| House of Quality | The specific matrix tool used in QFD’s first phase, translating customer needs into design requirements |
How are they related?
QFD is the full journey; the House of Quality is the first, most well-known leg of that journey. It’s easy to treat the two as interchangeable since the House of Quality is by far the most recognized part of QFD, but a complete QFD process actually continues well beyond this first matrix, a point covered in detail later in this article.
The Rooms of the House of Quality
Building on the shape explained above, here’s what actually goes into each section, using the example of a new smartphone (the same product category used in this page’s worked example).
Room 1: Customer Requirements and Importance Ratings
List what customers actually say they want, in their own terms: size, weight, ease of use, reliability, price, screen size, battery life, camera quality. Rate each need’s importance on a defined scale, commonly 1 to 5, then convert each into a percent importance by dividing its rating by the sum of all ratings.
Room 2: Design Requirements
List the technical characteristics the team can actually design and control: weight in grams, production cost, operating system, battery capacity, screen dimensions. These are the “Hows” that need to satisfy the “Whats” listed in Room 1.
Room 3: The Relationship Matrix
This is the central grid connecting every customer requirement to every design requirement, and it’s the section the existing page left incomplete. See the dedicated section below for exactly how this works.
Room 4 (The Roof): The Correlation Matrix
The triangular roof sitting above the design requirements shows how those requirements interact with each other, whether improving one helps or hurts another. A strong positive relationship (both requirements move in the same helpful direction) is often marked “++”; a strong negative relationship (improving one requirement makes another worse) is marked “–“, with blank cells indicating no meaningful interrelation.
Room 5: Competitive Assessment
A side-by-side comparison of how the current product and its competitors perform against each customer requirement, helping the team see where they’re already ahead and where a competitor has a real edge.
Room 6: Technical Priorities (the Foundation)
The calculated output: a ranked list of design requirements based on their combined importance and relationship scores, showing where the team should actually invest design and engineering effort.
How Does the Relationship Matrix Work?
This is the step the existing page’s instructions broke off mid-sentence (“use the following symbols,” with no symbols shown), and it’s the most mechanically important part of the entire tool.
The relationship matrix uses a small set of standard symbols, each carrying a specific numeric weight:
| Symbol | Relationship Strength | Typical Numeric Weight |
| ● (filled circle) | Strong relationship | 9 |
| ○ (open circle) | Medium relationship | 3 |
| △ (triangle) | Weak relationship | 1 |
| (blank) | No meaningful relationship | 0 |
For each cell in the matrix, the team asks: how strongly does this design requirement affect this customer need? If production cost has a strong effect on whether customers see the phone as “cheap,” that cell gets a 9. If battery capacity has only a weak, indirect effect on “easy to use,” that cell might get a 1, or be left blank entirely.
Also Read: Six Sigma at Boeing: A Century of Quality, a Decade of Reckoning
How Do You Calculate Technical Importance?
Once every relevant cell in the relationship matrix has a weight, technical importance for each design requirement is calculated with a straightforward formula:
Technical Importance Score = Σ (Customer Importance % × Relationship Weight), summed down the entire column for that design requirement.
Worked example: Suppose “screen size” has a customer importance of 4% (calculated from its rating relative to all customer ratings combined), and its relationship to a specific design requirement is rated as strong (weight of 9). That single contribution to the design requirement’s score is 4% × 9 = 0.36.
This calculation is repeated for every customer requirement connected to that design requirement, and the results are summed to produce its total technical importance score. Once every design requirement has a total score, dividing each by the sum of all totals produces a clean percentage, showing exactly where the highest-priority investment should go.
Where Did the House of Quality Come From?
Understanding the tool’s origin adds real context most competing pages skip entirely. Quality Function Deployment was developed in Japan by Dr. Yoji Akao, starting around 1966, building on ideas from the broader Japanese quality movement following World War II.
The methodology was first meaningfully demonstrated at Mitsubishi Heavy Industries’ Kobe Shipyard around 1972, where it was applied to genuinely complex ship design problems.
Toyota adopted the approach shortly after, reportedly reducing startup costs on new model launches significantly within a decade of adoption. QFD then spread to the United States through the 1980s, carried largely by Ford and Xerox, with Dr. Don Clausing at MIT playing a significant role in adapting and promoting the methodology for American manufacturers. From there, it became a standard tool within the broader Design for Six Sigma (DFSS) toolbox.
The Four Phases of QFD: What Comes After the House of Quality?
This is the connection the existing page never makes, and it’s directly relevant to SSDSI’s own content: the House of Quality is only Phase 1 of a complete, four-phase QFD cascade. Each phase’s output becomes the next phase’s input, carrying customer intent all the way from initial concept through to full production.
| Phase | What It Does |
| Phase 1: Product Planning (House of Quality) | Translates customer needs into prioritized design requirements |
| Phase 2: Parts Deployment | Translates design requirements into specific part or component characteristics |
| Phase 3: Process Planning | Translates part characteristics into the specific process steps needed to produce them |
| Phase 4: Production Planning | Translates process steps into the specific production controls, standards, and specifications needed to run reliably at scale |
Why does this matter to a Six Sigma practitioner specifically?
Phase 4 of QFD lands in exactly the same territory as a Six Sigma Control Plan, the document specifying the exact settings, checks, and controls needed to sustain a process. A team that runs the full QFD cascade, not just the House of Quality, effectively builds its own Control Plan as the natural final output of the process, with a direct, traceable line back to the original customer requirement that justified it.
Real-World Example: Smartphone House of Quality
Customer requirements are gathered and rated: size, weight, ease of use, reliability, price, screen size, battery life, and camera quality, each scored 1–5 for importance.
Design requirements are listed: overall weight, production cost, operating system, battery capacity, and screen dimensions.
The relationship matrix is completed: production cost is rated as strongly related (9) to the customer’s desire for a cheaper phone, while operating system and battery capacity are rated as having a more moderate relationship (3) to overall cost.
The correlation roof shows that battery capacity and weight have a negative interrelation (a bigger battery tends to add weight), marked accordingly, while operating system and battery life show a positive interrelation, since an efficient operating system extends battery life.
Competitive assessment shows the team is currently behind competitors specifically on battery life, adding weight to that requirement’s overall priority.
The result: technical priority scores reveal that production cost and battery capacity deserve the most design investment for this particular product, a specific, numbers-backed conclusion the team can now act on with confidence, rather than a general sense that “customers want a good phone.”
Common Mistakes When Building a House of Quality
- Skipping the numeric weighting in the relationship matrix. Symbols without their corresponding point values (9-3-1) make the technical priority calculation impossible to actually complete.
- Confusing the House of Quality with the entire QFD process. Treating the first matrix as the finish line misses the three additional phases that carry customer priorities all the way to production.
- Overloading the matrix with too many customer requirements at once. A House of Quality with dozens of unfiltered requirements becomes difficult to complete meaningfully; grouping or prioritizing requirements first (sometimes using a Kano model) keeps the matrix usable.
- Skipping the correlation roof entirely. Without it, the team can end up prioritizing two design requirements that actually conflict with each other, discovering the tension only after both are already in development.
- Treating the calculated technical priority scores as the final word. The scores are a strong, data-backed input to decision-making, not an automatic override of engineering judgment or business constraints.
Frequently Asked Questions on House of Quality
Q: What is a House of Quality?
A: The House of Quality is a matrix-based planning tool that translates customer requirements into prioritized, measurable technical design requirements. It’s the central, best-known tool within the broader Quality Function Deployment (QFD) methodology.
Q: Why is it called a “house” of quality?
A: Its finished matrix visually resembles a house: customer needs on the left wall, design requirements across the top, a relationship matrix as the main body, and a triangular correlation matrix as the roof, with technical priority scores forming the foundation at the bottom.
Q: What is the difference between House of Quality and QFD?
A: QFD is the overall four-phase methodology for translating customer needs into product, process, and production decisions. The House of Quality is specifically the first matrix used in QFD’s first phase.
Q: What are the rooms of the House of Quality?
A: Common rooms include customer requirements and importance ratings, design requirements, the relationship matrix connecting them, the correlation matrix (roof), a competitive assessment, and the calculated technical priority scores.
Q: What symbols are used in the relationship matrix?
A: A standard weighting typically uses a filled circle for a strong relationship (weight of 9), an open circle for medium (weight of 3), and a triangle for weak (weight of 1), with blank cells indicating no meaningful relationship.
Q: Who invented the House of Quality?
A: Dr. Yoji Akao developed Quality Function Deployment, including the House of Quality, in Japan starting around 1966, first meaningfully demonstrated at Mitsubishi Heavy Industries’ Kobe Shipyard around 1972.
Final Words
The House of Quality earns its name from its actual shape, and understanding that shape, customer needs, design requirements, a relationship matrix, and a correlation roof, makes the tool far easier to build correctly than treating it as an abstract checklist.
Completing the relationship matrix with real numeric weighting, and recognizing that the House of Quality is only the first of four QFD phases rather than the entire process, is what turns this tool from a one-time customer-needs exercise into a traceable line running all the way from Voice of the Customer to a production-ready Control Plan.
Building a House of Quality that actually produces a defensible, numbers-backed priority list, not just a filled-in template, is a core DFSS skill covered in depth in SSDSI’s training.
Six Sigma Development Solutions, Inc. (SSDSI) is IASSC-accredited and 5-star rated on Google Reviews, having certified 5,322+ professionals across 600+ organizations in 52 cities. Our onsite, live virtual, public, and online Black Belt training covers QFD, the House of Quality, and the full DFSS toolkit in the depth needed to translate real customer requirements into a working Control Plan. Explore SSDSI’s Black Belt certification to build that capability.
About Six Sigma Development Solutions, Inc.
Six Sigma Development Solutions, Inc. offers onsite, public, and virtual Lean Six Sigma certification training. We are an Accredited Training Organization by the IASSC (International Association of Six Sigma Certification). We offer Lean Six Sigma Green Belt, Black Belt, and Yellow Belt, as well as LEAN certifications.
Book a Call and Let us know how we can help meet your training needs.
