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"We love alternating tread stairs because they are such great space savers; this photo shows the comparison. So why don't we see them more often? For one thing, they don't meet a lot of building codes. Even Lapayre Stair, a big manufacturer, has an entire"^^<http://www.w3.org/2001/XMLSchema#string>
<http://www.treehugger.com/corporate-responsibility/alternating-tread-stairs-a-roundup.html>