From the 2003 IRC Commentary (and why the number is different).
- R408.4 Removal of debris.
The under-floor grade shall be cleaned of all vegetation and organic material. All wood forms used for placing concrete shall be removed before a building is occupied or used for any purpose. All construction materials shall be removed before a building is occupied or used for any purpose.
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Vegetation, stumps, roots, and other matter left in an excavation around a building are major causes of termite infestation and moisture problems. As such material decays, the ground settles, negating the original drainage plan. Even before decay, the material provides pockets for water accumulation, which can have subsequent destructive impact on the structure. To eliminate a natural attraction to termites, insects, or animals, all vegetation and organic material must be cleared.
What is cardboard made from?