The strongest evidence most businesses have.
WHY THEY WORK
A visitor deciding whether to hire you wants evidence you have done this before, for someone like them.
THE STRUCTURE
What the client needed What the situation was What you did What the outcome was
Four short sections. A case study does not need to be long.
WHAT MAKES THEM CONVINCING
Specifics. Names, places, numbers, timescales. Photographs of the actual work. A quotation from the client. Honest mention of a difficulty and how it was handled.
WHAT MAKES THEM WEAK
Generalities No photographs No named client, where naming is possible Nothing that could not be said about any project
PERMISSION
Ask before publishing client names or details. Most agree, and asking is both courteous and sometimes necessary.
HOW MANY
Three or four done properly beats twenty listed briefly.
FOR TRADES
Before and after photographs, taken from the same position, are the entire case study. Take them as you work.