When talking about the growth of a production plant, which of the following is correct, and why?
We are growing in area and number of employees.
Or:
We are growing in area size and number of employees.
When talking about the growth of a production plant, which of the following is correct, and why?
We are growing in area and number of employees.
Or:
We are growing in area size and number of employees.
"area size" is not an idiomatic phrase. "area" already refers to the amount of space, adding "size" is redundant.
So "growing in area" is the more correct one of the two phrases.
In the US you are likely to hear square footage, meaning area when measured in units of square feet.
You might also hear floor space or floor area to indicate the interior area of a building.
In your examples, I don't believe "area size" would be commonly used because it is redundant. Either area or size might be used alone, as in
We are increasing the size/area/floor space/square footage of our production facility.
A colloquialism is footprint.
As the attestations show, it is a very common phrase in the context of business expansion, and so anyone who reads about business is not likely to confuse it with "environmental footprint" or "carbon footprint" which are a measure of a company's deleterious effects upon the planet's natural environment.
The company's footprint is getting larger. Not only has our workforce doubled in size, we have purchased land and built new facilities.