I've just opened up a basement window another 20" down from original to make legal another bedroom and bathroom I have in the basement.

What I have is a wood fram that will get an open-able window/door for emergency egress (escape window basically).

My question is this:

I have about 3/4-1" gap around the sides of the window (the top and bottom are only about 1/4" and caulking would be ok), I've used an expansion foam to weatherize it, but I'm wondering if I can fill the gap between the cement wall opening and the (treated 2x10") wood frame with latex treated grout-I feel this would look much better than using Aluminum trim to cover the gap.

My concerns:

Will the latex treated grout tolerate the expansion and contraction of the wood VS cement, or will it start to crack??

Thanks in advance for your information!

Cheers
Brian G.