In a single-family house only a single interior stair is normally required from any living space above or below the ground floor and one window in each bedroom large enough for emergency exit. If there is a second dwelling unit two stairs would be required. Are you renting the space?

How do you get into the attic if there are no stairs?

If you have habitable space you most likely need some stairs to get to it.

bigdogs, just where do you live anyway????

Obviously if you have a 2nd level living area, you have to have a staircase to reach that level but it would normally be an INTERIOR staircase, not an exterior one. (By "interior" I mean a staircase that is inside the house versus an "exterior" one that you can access directly from the yard without going into the lower level of the house.)

If you have a finished attic, then code might (and probably does) require you to have a finished permanent staircase up to the attic rather than a pull-down staircase or an attic access that you use a ladder to climb up to.

A finished staircase from the lower living area to the attic would still be an INTERIOR staircase. It would only be an EXTERIOR staircase if you had to go outside your house to climb the stairs to the attic.

You should certainly be able to look around at all the two-story houses in your town to find out if your city's code requires EXTERIOR staircases on all two story homes. You would be able to see these EXTERIOR staircases from the outside of every two story house.

I have never heard of such a code anywhere.

At first glance, it seems silly: an EXTERIOR stair?

But if there are no egress windows up there, or if the egress is very high off the ground, I can imagine a situation where a stair might be needed.

Fire escapes are not normally required on two or less story buildings. Local authorities can increase requirements, so you need to ask locally. Ask whomever is giving you this information to explicitly cite the source of the requirement. If they are a governmental entity, they MUST provide this information.

If they are not a government entity, contact the county or city building department and ask them.

Could the exterior stair case be because the windows you have in the finished attic are considered too small for egress? I assume you have windows.

If you are making major improvements to your house you should own a copy of the building code and any other applicable ordinances. Call the building department and ask what they are and buy them from the town or over the internet. Meeting the building code is your responsibility.

"exterior staircase on every two story house that is built?
exterior staircase on home with finished attic?
exterior staircase on home with unfinished attic?"

None of the above here. We have an unfinished attic (it's the third level) that is ready to be finished (meaning, the floor and joists were designed to hold living space). It's accessed via a staircase from the second level (just like a basement is accessed, but in reverse). The door is insulated to separate the heated from non heated space. There are windows in the attic (2, mulled together), but they are not egress size and don't need to be even if the attic is finished UNLESS we put a bedroom up there.

Around here I have seen buildings with exterior staircases, but it is always where there is a separate living space (house divided into condos or apartments, etc.).

Some building inspectors like to enforce the code that is in their head (the code they wish existed) rather than the code that actually exists. Just make sure that isn't happening to you. There should be a copy of the code at town hall. If you can't find what he is referencing in there just tell him you couldn't find the section and would he please provide it to you. Be polite (it's in your best interests not to get on the guy's bad side).

How does the code define the difference between a two story house and a one story house with a finished attic? Can't a one store house with an unfinished attic become a two story house when the attic is finished?

Building codes in general require that the ground floor have two exits doors to the exterior as far apart as practical and there must be at least one egress path from all other habitable floors above or below the ground floor leading to these exits. In addition emergency escape and rescue windows are required in all bedroom on all levels.

Restrictions on the number of floors in a house is a zoning issue. I can't imagine why there would be a building code requirement for an exterior stairway in any home but it might be a "compliance alternative" allowed by the building inspector when it is not possible to install a stairway inside the house.