Question

what do we call a small room at the top of the house

Answer 1

The following words can be used for a small room at the top of the house:
a) Attic
b) Garret
c) Loft

We use this room predominantly for storing things. In very rare cases, someone may live in this room also.

Answer 2

We call a small room at the top of the house as "attic" and it is also referred as "loft".

This area of the house is very small in size, and will be used for compact purpose even for a single person to stay and present at the top position of the house and generally used for storage purpose.

Hence the option for the given question will be attic or loft.