Without sounding jocular;
I thought Beaver board was the war cry in old frat houses
never the less sodium silicate was the early store bought water proofing
agent used by masons in Ireland Scotland and the U.K;
 it is the base ingredient for Kiem  mineral systems; but perhaps Mike E.
could enlighten us  how it actually works and what its limitations are.
Best Michael
PS..by the way I got beavers in my Bass pond,
I feel like Wylie E. Coyotee;
every new kind of trap I set blows up in my face
as they all laugh and slap their tails on the bank....I'll get them varmits
yet!