
<blockquote>
<p>A building properly conceived is several layers of longevity.</p>
</blockquote>

<p>Duffy called these shearing layers. Each of the layers moves at a different timescale. Brand expanded on the idea, proposing six alliterative layers:</p>

<ol>
<li><strong>Site</strong>—the physical location of a building only changes on a geological timescale.</li>
<li><strong>Structure</strong>—the building itself can last for centuries.</li>
<li><strong>Skin</strong>—the exterior surface gets a 