What type of house is easiest to Duplex?
Great question. While you could potentially duplex almost any house, there is a few things that are easier with certain styles.
For instance, if you were to say try to use a 2-Story House. You would need a separate entrance right off the bat, for the basement apartment. Some 2-story homes have a side entrance, which you could use, perhaps needing to isolate the side entrance and downstairs door somehow from the rest of the home. Usually I found that 2-Story homes layout left you with a very small basement though, at best you would be able to turn it into a tiny 1-bedroom unit, or a glorified bachelor suite. It could work though.
Side-split can sometimes work too. Again, you are usually limited in size with a side-split. There are the odd 5 level side-splits, however the most we saw were 4 level ones. This leaves little room for a 2-bedroom basement unit, however, with the right layout it could work for a 1-bedroom. Not all side-splits can work though. Often there is also a garage attached to these types of homes that take over a big portion of the lower units layout.
Raise-bungalows are great. But you are usually limited in size. Most bungalows are 2-3 bedrooms upstairs. Often its a one bathroom unit. If you were hoping for an ensuite upstairs, it might be hard. But what I like about raise-bungalows is the windows are normally larger in the basement. As well, the downstairs layout is usually mirror to the upstairs, meaning you have a good space to work with. And usually the basement is a walkout, this is a great start!
Back-splits are my favorite. Usually the back-splits are setup with either 4 or 5 levels, depending on location. We found a back-split that was 5 levels. This meant two floors were above ground, this had a step up, then front entrance. And then there was the ground floor, which had a side entrance. And then you step down into a sub basement, and finally the final basement. The sub basement required larger windows, but were still above grade, which was very easy to do. But the basement level needed to excavate and install much larger windows as well as deeper window wells. In the end we were left with a 2 bedroom/1 bath upper apartment. And a 3 bedroom/3 bath lower apartment. The basement apartment had a ground floor kitchen/livingroom, which had alot of natural light, and the two basements made nice bedrooms, with enlarged windows. The backyard was only accessible from the lower apartment, and side entrance became the lower unit’s front door. This was the best layout we ever found. The lower unit also had access to the garage. Separating these units only required closing off an open half wall, as well as closing off a 3-step stairway that connected two floors. Once this area was closed off, the units easily became separate units with separate entrances. The other nice feature of the backsplit, is that the mechanical room is completely under the lower unit. If say, you were to have a different unit above the mechanical room, it would require either (1) a sprinkler system installed; or (2) to completely drywall the mechanical room with Fire Rated Type X Drywall. This gets very finicky when you have ductwork and pipes going thru the mechanical room. So I say again, back-splits were my favorite!