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Is OSB a class C rated interior finish product

Question asked by rfdacm02 on Jun 12, 2020
Latest reply on Jun 15, 2020 by milt.werner

We have multiple independent projects where the builder has used OSB as an interior finish product to minimize damage to sheetrock. In all of these projects, per the LSC they must meet as Class C interior Finish.  In general most OSB we see doesn't have a stamped rating of Class C or any outward indication that it has been tested to ASTM E84. That said, the American Wood Council has a document (attached) showing the general flame spread/smoke production of various types of wood, and wood products. Under their Table 2, they list OSB  and state it has a a class C flame spread rating and show  a smoke production value within the acceptable 0-450.


My question is: Are we to accept this documents findings and allow these products or are the individual manufacturers still required to have a third party test and then publish the listing and installation requirements to meet the listing?