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Introduction: What Is Happening in Rooftop Greening

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This page is intended to help you grasp the overall picture in just a few minutes.

Why Does Rooftop Greening Often Fail?

When researching rooftop greening, you may come across comments such as:

• “The condition deteriorated within a few years.”
• “The plants didn’t die, but the greenery never spread.”
• “Maintenance couldn’t be sustained and the area was abandoned.”
• “It eventually became overrun with weeds.”

These are not unusual or exceptional failures.
Similar situations are occurring at many sites.

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Is This Really “Someone’s Mistake”?

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These outcomes are often explained as problems of construction or maintenance.

However, what is frequently overlooked is the fact that
the same results are being repeated in different locations.

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The Reasons Often Lie Much Earlier

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When cases where rooftop greening fails to take hold are examined,
the underlying issues are often found not after construction, but in the initial decisions, such as:

• Planning
• Design
• The way plants and methods are selected
• The choice of rooftop greening products

Those early judgments simply take time to surface as visible results.

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Rooftops Are Not the Same as Ground-Level Environments

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Rooftops are subject to conditions that differ from those on the ground, such as:

• Greater exposure to wind and solar radiation
• A tendency toward dryness
• Limited available soil volume

How these conditions are understood becomes the foundation for all subsequent decisions.

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What This Site Addresses

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This site does not recommend specific products or methods.

Instead, it focuses on organizing:

• Why rooftop greening fails to take hold
• What kinds of accumulated judgments lead to those outcomes

—by examining them as structures of thinking, rather than as isolated problems.

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For Those Who Want to Go Further

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・Understanding the Structure That Enables Sound Judgment▶
・Structures That Lead to Failure▶

These two pages explore the underlying ideas in more concrete terms.

In addition, the following sections are available:

・Common Misconceptions & FAQ▶
・Terminology & Definitions▶

These pages clarify assumptions that often lead to misjudgment
and explain how key terms are used within this site.

If questions or uncertainties arise while reading,
please feel free to refer to them as needed.