I have set my sun box to zombie factory so everything is dark dark!

However somehow some light is appearing at the base of some of my walls, and simply can't seem to get rid of it!  I've tried to throw the fall down well beneath the floor.  The only thing I've yet to try is to add a roof, however, I don't think I should have to add a roof in order to get rid of these pesky light seeps.

I am sure there is a simple way of doing this, so I hope, that someone would be nice enough to explain it to me!

Thanks

Place a shadow brush at the base of your walls.