I'd call it a gut remodel. But if you're looking for an official definition, check with your local Building Official.

Whatever you call it, it will require a building permit.

I will be permitting. 2 concerns I have. 1) I don’t want it to impact my taxes as “new construction” 2) The code changed (in the way we calculate FAR -floor area ratio) since the sunroom was built in 1992 and now that square footage may put us over. So I was thinking if it was considered a remodel, it might not be an issue. I’m not sure how that works...but seems like I should be allowed to have the same square footage that I have now.

Only one way to find out. Hint: see my post above...

"Is this considered new construction or a remodel?"

Neither, it would be an addition. Good try, but you couldn't fool me.

@Mark - what does that mean? What is the difference between an "addition" and "new construction"? We are paying property taxes on the permitted sun room. So I guess that is where I am confused on how this changes. Either way, we are working with our architect on submitting the plans to the city. I was just doing my own research on the side, to see if I could understand.

A sunroom is an outdoor space with a roof, attached to a house. It isn’t counted as heated and cooled space, because it isn’t heated and cooled. Nor is it built to indoor habitable space standards.

To make it into indoor habitable spaces means that you are actually adding a new construction habitable space addition to the home, after demolishing and rebuilding. Adding a code compliant foundation under an existing building isn’t as easy as you think. Which is why demolishing and rebuilding to the higher current code standard may be the best and cheapest approach.

If you are insulating it, I'm assuming you will be heating/cooling it as well? If so, it is no longer a sunroom but an addition to your home that is now counted as "living square footage" when it comes down to tax purposes.

You're not going to get a reliable answer here as we can't predict how your local building department will treat it. Talk to them...

Every jurisdiction has its own rules on what they require a permit for and how they assess taxes. I live in an incorporated village, and their rules and regs are much stricter than those in the town/county/state I live in. And there is a difference between the building department and the tax assessor's office. So yes, your best bet is to inquire of your local authorities for the answer.

Sounds like a great project--good luck!

If you want building code advice its helpful to reveal the code that applies or where the project is located.

The IRC doesn't use the term "new construction". The code applies to the "construction, alteration, movement, enlargement, replacement, repair, equipment, use and occupancy, location, removal and demolition of detached one and two family dwellings and townhouses..." Assessors may use different terms for determining your property taxes so you need to ask them.

If the code is a recent version of the IRC, the categories of remedial work are "Additions, Alterations, and Repairs" all of which must conform to "the requirements for a new structure without requiring the existing structure to comply with the requirements of the building code". If your jurisdiction has adopted the International Existing Building Code, there will be additional special provisions for the 3 categories.

Since you will be removing all of the existing structure, this work should be considered an Addition and subject to one of the 5 categories of section R301.2.1.1.1 Sunrooms.

"Remodel" would imply that there is an existing structure that will be altered in some fashion.

"New construction" would imply an existing structure is not involved in the project.

"Addition" would imply there is an existing structure that is getting larger.

Since you will "demo it and rebuild it", a portion of the home will be removed for a new structure to be added to the existing home, I would call it an addition.

The definition of the terminology will be determined by the powers to be. I have experienced a Zoning Administrator for one of my projects that has traveled to Pluto to obtain definitions of a few words to apply to my project, totally ignoring the work of Danial Webster and others here on Earth. I digress.

I am always amazed that “property taxes” drive decisions on what is the best space for your family. For years, our neighbors refused to let the county pave our road! We suffered from constant dust and dirt, ruts, muddy conditions, and broken tie rods. Finally the county paved the road over the objections. Our property taxes didn’t go up but it certainly was easier to sell our house for more money. I have heard of people who won’t paint their house and let the shrubbery grow wild just to avoid higher taxes. If you have questions about tax consequences, you should talk to the tax assessor’s office in your county. Each county in America has different rules. None of us can truthfully answer the question. For example, I live in a county that does not require a building permit for remodeling or new construction. I used to live in a county that had four different building departments, each with its own peculiar set of rules. Do your own homework to get the best answer.