This foam expands very rapidly. It is best to clean up any excess foam when it is in a liquid state. Once it dries and cures, it is harder than styrofoam and will require a knife to trim. I used it to seal the spaces around my attached garage in the condo and I can immediately tell that it did the job of sealing the air space. It fills spaces/voids/gaps very easily, but each can doesn't cover a whole lot of space. I needed 2 cans just to seal the lower wall gaps in my 2 car garage.