A clean burning fire does not leave soot.
Sounds like a smoldering fire.
How was the condition of the wood?
What type of wood?
Was it dried and seasoned?
Moldy or funky wood surface?
Green (wet) wood?
Custom Klose Backyard Chef... of Snot, and a 22.5 WSM
Lang 84 Deluxe kitchen, Lang 60 Mobile - The Damsel II, Lang 48 Patio - The Damsel, Bubba Keg Grill - RIP, Double Barrel Smoker and a BSKD