The 21 day design & permit set

[Reece Carter]

In helping a local Atlanta builder / developer flip bungalows properties into attractive midsized neighborhood properties, I have been challenged with the ability to produce a permit set thats to be entered into permit application within 21 days; basically taking advantage of the due diligence period before the properties is closed. In a nutshell, I am doing
AsBuilts (floor plan & elevations),
schematic design (new layout),
CAD input of the layout, new elevations,
Broadcasting plans for budget numbers from key vendors
CAD sections and details,
coordination of structural framing from manufacturer and vendors,
foundation certificate
coordinating expediter

All in the effort of getting the permit application number by the end of day 21.

Some difficulties that we are having are
Varied municipalities / varied plan submittal requirements; the requirements are such a moving target from office to office and day to day, it seems.
Response times from all involved (Quotes from vendors and trades)

How many of you take advantage of the due diligence period like that?
Whats a typical timeline for such a thing?