This question falls dangerously close to being a software question, but it's definitely specific to DIY...
My house is around 100 years old. Off-the-shelf home design programs have nice libraries of drop-on components like walls and windows that can be adjusted somewhat to fit, but they are basically useless when trying to realistically match older wall sizes, window types, molding, etc.
I love Google Sketch-up and have successfully created a few basic plans in it, but I'm really tired of reinventing the wheel constantly, or compromising my 3D design and having just a big box rather than a detailed rendering.
I would love, for instance, to be able to create a wall that is exactly 9'4" tall, 5 1/4" inches thick, with a baseboard on each side that is 3/4" x 8" with a 1/2" turn edge, and quarter-round at the bottom. Then I'd like to be able to drop that into Sketch-up and simply resize it to create a custom wall that is exactly like those in my house.
Same goes with the windows, doors, trim, and various other odds and ends.
My experience, however, has been that SU can't think of anything as an "object", only as edges and surfaces. So, trying to reuse shapes is a bit of a pain, as is punching through walls and adding realistic windows, etc.
So, any tips on how to properly component-ize my designs?