someone who has read the book

i dont get if its the house or the architect thhat brought the evil? the architect had other bad things happen with his other projects--so i thought it was him. but they meant to burn the house down without him in it after she clearly says with conviction "its him and everything he does." --- yet they didnt plan to kill him only the house. and at the end, they foreshadow that because they still had the plans it didnt matter if he was dead cause it was actually just the house? or had he already placed his evil into the making of the house??? i really dont get it. but i want to because i enjoyed the film.