In my fantasy novel, I have elves. Unlike most elves, these do not use magic. The architecture of elves is usually depicted as trees that have been flowingly shaped into houses and graceful structures. Without magic, this is not the case. Also, my elves are significantly weaker than humans, and as such, are not the greatest at stone quarries.
At the same time, these are elves, and as such, they appreciate nature and would rather not chop it down to make houses. Because of that, 'tree-forming' and lumber production are not options, and stone is limited. What can my elves use to build their villages and cities?
EDIT: I've marked the answer by Will Martin as I think it supplied the most options, but all of the answers here gave me great ideas, and I think the answer to my specific issue is a combonation. I think sod houses would be a good place to start. (Where they get them from can later be turned into farm land. Yes, my elves farm.) Clay/Mud bricks can be used on the interior and exterior to add waterproofing (nothing saying the elves can't burn dead wood in a furnace to speed the process up).
Pleaching of tree branches into the walls could help with support, though in the long term it could create some problems as the trees naturally expand into the house. Alternatively, bamboo could be used, or some other plant that expands exclusively upwards. Eventually, the sod would wash away, leaving bricks with flora growing on them for a very Elven feel. All that would be seen would be a mound of grass. Animal hides could be used as doors, to separate rooms, and as blankets. Additionally, large animal bones could be used to support the walls.