Mulch that is 4 inches or more is too thick, and creates conditions conducive to termites. It offers a bridge into a structure that allows termites to bypass a soil termiticide treatment, and also obscures the foundation during inspections.
An inspection gap between mulch and siding should be 6 inches or wider, so inspectors can determine whether mud tubes have been built. Ideally, a 6- to 12-inch mulch-free zone should exist around the foundation. A dual rake/hoe hand tool can help pull away thick layers of mulch during the inspection process.
from Pest Management Professional http://www.mypmp.net/2018/08/09/overcoming-foundation-inspections-hindered-by-mulch/
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