We are going to have a support beam and then the columns. What do you mean the span? I guess we are trying to determine whether to take down the entire wall or just a part of the wall and leave room for double wall ovens....and we are trying to determine the average space between columns.

Meaning, is 7 feet of space between the two columns too little?

Too little for what?

The answer is, it depends.

Explaining what you are doing and why, along with diagrams, pictures etc will help others understand and be able to provide better suggestions.

and replace with decorative columns

I assume you mean ' replace with support columns that will be clad in something to look nice'.

As millworkman said, decorative columns aren't for support. They are for decoration.

When messing with anything involving the support of a building, getting an engineer involved is extremely important. There are so many factors that go into this that you won't get a satisfactory answer on the internet. And you really don't want to guess and be wrong and have the building collapse.

agreed. we are pulling a permit. however, we are deciding how much of the wall we should take down versus keeping up a part of the wall...

So if you are pulling a permit and having an engineer design it, why don't you ask him how far apart the columns can be?

If you add the right size header, you may not even need any support columns in a 13 foot span. The size of the header depends on the material (steel vs wood) and the amount of weight it has to support.

If you are looking to have a perfectly flat ceiling between the two areas (ie. no header sticking down) you can also possibly use a steel header retrofitted into the ceiling to carry the weight.

As I said, there are so many options with a wide variety of how much you are willing to spend, that an engineer needs to be consulted for a real answer.

You will have a lot of latitude in spacing for such a small span (probably lots of ways to do it with no exposed posts at all), so yes, you must consider the structural aspect, but your question is still very appropriate. A few inches can make a big difference in appearance.

I suggest reading up on "golden rectangles" and other ratios that seem to be pleasing to human aesthetics (I like Fibonacci series quite well). Classical architecture makes extensive use of the "golden ratio", about 1.618:1. You won't go wrong using it to design the space. (Look at pictures of the Parthenon for examples of how it was used in most every aspect of the design)

Talk to a structural engineer. If it's above a basement, that may not be okay.