Bora-Care can be applied to oriented strand board (OSB) that do has not be painted, stained or sealed per the manufacturer. Please refer to the product label for more detailed information by clicking the link below.
http://www.domyownpestcontrol.com/msds/boracare_label.pdf
We recommend doing the treatment with the Fipronil or Altriset first, waiting 90 days and then following up with the Boracare. This will allow the termites to go back to the colony with the active ingredient on their body and pass it around the colony causing the entire colony to collapse. If you treat with Boracare first, you risk only killing the termites present and not getting rid of the entire colony.
Since all surfaces of the wood need to be treated, we would recommend you remove any item that is blocking the application from reaching the wood. You should drill through any layered beam to get the solution all the way to the next beam when necessary.