dividing the house like you have to go outside to go to the other house or simply dividing two spaces/areas with a wall? kasi if you're going to divide the house (literally), you really need an architect since structural na siya but if it is simply dividing the two spaces with a wall, an ID will do. I just hope you have a blueprint copy of the house so the ID can plan the areas properly. S/he needs to see kasi if may kelangan iwasan na pipes, beam, wires, etc. I suggest to get a contractor who is also an architect, in that way, you and the ID can get "free" tips and suggestions while doing the project.