I like this. Not seeing a way to put the "B" in the building, but maybe (door on the left to leave the bottom of the F open?). Might want to play with colors a bit. Also would be even more interested if the building icon could be stand alone (for occasional use without the Flint Builders LLC below) and the entire piece would work as a black and white logo.
#38 has a subtle "B" in the bottom shadow of the "F". there are also some thoughts on an added door and color combinations as well. if you have other ideas, please let me know.