Are you trying to get construction skills to solve a puzzle or to build another hut? If you have 65 people, you have already built all of the huts and reached the maximum population. There aren't any more huts to build, even though you may see the message, "There isn't enough housing" when you try to breed. If you're trying to develop construction skills to solve a puzzle, helping you with that depends (as Savi said) on knowing which puzzles you've already completed.