Answer:
Prefabricated houses were built in my home town of Clydebank, Scotland when many houses were bombed during the 2nd world war.
They were homes that were quickly erected, i.e. they arrived ready built and designed to last only around 10 years although many lasted a lot longer than that.
They tended to be 2-3 bedroom homes, about 1000-1200 square feet in total.