The construction complexity of building furniture and constructing a complex building is exactly the same, the only difference is the amount of resources needed. There is always a maximum of 5 different resources for each construction or item to craft.
Difficulty should increase with more complex skills (high tier skills).
Construction materials preparation < Construction < Masonry < Architecture
1) Construction materials preparation
Flatten ground, set construction sign, gather resources, build
Flatten ground, set sign/building outlines, gather resources, build walls, gather resources, build roof
Flatten ground, set sign, gather resources, build fundament/cellar, ... , build roof
Flatten ground, set sign, gather resources, build fundament, gather resources, build scaffolding, ... , build roof
You could also add an extra step for large buildings, build building crane.
This would definatelly make it more interesting to build more complex buildings.