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.
Ad. The value of this system for paper sizes is that each size is proportionately equal to the next. A4 paper, for example, is about 21 cm by 29.7 cm (about 8.27 inches by 11.75 inches), while A3 is 29.7 cm by 42 cm (around 11.75 inches by 16.5 inches).tandard letter size paper in the US is 8.5 inches by 11 inches (about 21.5 cm by 27.9 cm), while legal size paper is 8.5 inches by 14 inches (around 21.5 cm by 35.56 cm).