Analysis
NAICS 44418 is the 2022 NAICS industry for other building material dealers, part of 4441 (Building Material and Supplies Dealers).
It has only one more detailed code, 444180, which covers exactly the same activities; the definition, index entries and statistics are on that page.
County Business Patterns publishes no national count for it, either because the code is out of the survey's scope or because the figures are suppressed to protect individual businesses.
Official definition
See industry description for 444180.
Source: US Census Bureau, NAICS 2022 Manual.