This shopfront is on Main Street, but in a group of detached dwellings (houses). To protect the character of this area, it could be coded T4-O, which would allow the looser form of T4 while preserving the commercial rights. (O stands for Open Function.)

The glazing is 30% of the first floor facade. Percentage of glazing is something that should be carefully calibrated to local character. You may want both minimums and maximums.


To measure glazing percentages on photographs:
Using Histogram>Show Statistics, record the number of pixels in the total first floor facade, then select only the glazing, then record the pixels again. Next, divide smaller number into larger in a percentage calculator.
For best results shoot the facade straight on with no diminishing perspective. (It will work with vertical or horizontal keystoning only if the glazing is symmetrical in the same direction as the keystoning. )