Here is the full list of all 14 Gnomes & Co: The Art of the Build achievements.
Solved a level within the par time
Solved 5 levels within their par times
Solved 15 levels within the par time
Solved 50 levels within the par time
Solved a level within the challenge time
Solved 5 levels within their challenge times
Solved 15 levels within their challenge times
Solved 50 levels within their challenge times
Solved a level faster than the challenge time!
Solved 5 levels faster than their challenge times!
Solved 15 levels faster than their challenge times!
Solved all levels faster than their challenge times!
Have 1 or more wasted blocks while building a product.
Make 2 or more products in a single loop.