You will need to consider the siding and roofing materials you would like to use to finish this space. And you might weigh the quality of exterior materials against their visibility. Also in the cost of the addition, be careful to factor in the permits needed and the work needed to prepare the foundation.
Envelope size - 4-3/8 x 5-3/4. Card paper size - 5-1/2 x 8-1/2 (half a letter sized sheet). Finished card size - 4-1/4 x 5-1/2. A4: Envelope size - 4-3/4 x 6-1/4. Card Paper Size 8 x 12-1/4. Card finished size - 4-1/2 x 6-1/8.
1 A5 is twice the size of A6. 2  A5 is half the size of A4, and one quarter the size of A3. 3  A5 is one eighth the size of A2, and sixteen times the size of A1,  A5 is thirty two times the size of A0.