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Use a lightweight growing medium.

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Topsoil (soil from the garden) is not used for green roofs because it's usually too heavy and tends to become too compacted. Use a mixture of organic and inorganic materials. Focus on keeping the elements lightweight but water retaining. {"smallUrl":"https:\/\/www.wikihow.com\/images\/thumb\/c\/c1\/Build-a-Green-Roof-Step-6Bullet1-Version-2.jpg\/v4-460px-Build-a-Green-Roof-Step-6Bullet1-Version-2.jpg","bigUrl":"\/images\/thumb\/c\/c1\/Build-a-Green-Roof-Step-6Bullet1-Version-2.jpg\/aid688104-v4-728px-Build-a-Green-Roof-Step-6Bullet1-Version-2.jpg","smallWidth":460,"smallHeight":345,"bigWidth":"728","bigHeight":"546","licensing":"<div class="mw-parser-output"><p>License: <a rel="nofollow" class="external text" href="https:\/\/creativecommons.org\/licenses\/by-nc-sa\/3.0\/">Creative Commons<\/a><br>
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<\/p><\/div>"} Roof growing mediums are usually fabricated from variances of primarily expanded shale, perlite, coconut husk, and/or peat moss. {"smallUrl":"https:\/\/www.wikihow.com\/images\/thumb\/2\/2c\/Build-a-Green-Roof-Step-6Bullet2-Version-2.jpg\/v4-460px-Build-a-Green-Roof-Step-6Bullet2-Version-2.jpg","bigUrl":"\/images\/thumb\/2\/2c\/Build-a-Green-Roof-Step-6Bullet2-Version-2.jpg\/aid688104-v4-728px-Build-a-Green-Roof-Step-6Bullet2-Version-2.jpg","smallWidth":460,"smallHeight":345,"bigWidth":"728","bigHeight":"546","licensing":"<div class="mw-parser-output"><p>License: <a rel="nofollow" class="external text" href="https:\/\/creativecommons.org\/licenses\/by-nc-sa\/3.0\/">Creative Commons<\/a><br>
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