Plot hole: Not far into the movie, Starla decides to check out the basement to see what Grant's been up to. As soon as the door is opened she reels from the stench and we discover that it's full of rotting meat and dead animals. In reality, the whole house would have smelt like an abattoir for days before hand and the stench would have permeated out into the neighbourhood. A non-airtight wooden door would not have kept that kind of smell located to the basement only.
Continuity mistake: When Grant is making the nest of leaves in his basement the morning after being infected, we see him throw the large bag offscreen. In the next shot the bag is nowhere to be seen. Then in the very next shot the huge bag is suddenly lying on the floor right beside the pile of leaves.