sspanzer:
In answer to your question.
Here are the following references to use when making your building:
Average Brick: Length 3.1 mm Width 1.5 mm Thickness 1.6 mm in 1:72 Scale
Door 6' 6'' in 1:1 Scale = 28 mm in 1:72 Scale
Window 4' 0" in 1:1 Scale = 17 mm in 1:72 Scale
These are the basics of measurments you will need for construction. I find it easier to draw my plan out in scale and make copies to use as templates for laying out the design of the building.
Hope this helps. The other suggestion is obtain good references prior to beginning. One book I ould suggest is Roy Porter's - Model Buildings Masterclass - Windrow & Greene Publishing
It is an excellent book and full of all kinds of reference material for many subjects.
Cheers;
Gregory