I still need to come up with a good porch module for wrap around porches and the like, but in the meantime with some careful use of the SUBTRACT function one can get pretty close:
The model can be viewed here:
https://3dwarehouse.sketchup.com/model/64c6616c-bbfb-4323-98da-e6c60fa3a522/Wrap-Around-Porch
The model can be viewed here:
https://3dwarehouse.sketchup.com/model/64c6616c-bbfb-4323-98da-e6c60fa3a522/Wrap-Around-Porch