The Collaborative International Dictionary of English v.0.48:

carriage house \carriage house\ n.
   a small building usually near a large residence or part of an
   estate, used for keeping coaches, carriages, or other
   vehicles; -- also called coach house. It is now (1998)
   obsolescent and its function has been taken over by the
   garage, which is usually attached to a residence or main
   building. Carriage houses are still found on older estates,
   though not usually used for their original purpose.
   [PJC]

WordNet (r) 3.0 (2006):

coach house
    n 1: a small building for housing coaches and carriages and
         other vehicles [syn: coach house, carriage house,
         remise]