I need pics of the house for sure . How are you planning on accessing the deck and what use will it be. In my experience these type decks are rarely used except for the first little while. More info and some pictures will help us.

The home was built in 1863 - it's got some years under its belt. I'd like to access the deck via stairs coming up from the patio as well as through an exit built into the side wall where a window now is.

What is the distance between the floor and the window sill on the 2nd floor and what is the ceiling height on the 1st floor?

~19" to window sill, 8' ceiling height. The window overlooking the roof will not be used as the exit because of the height of the pitched roof - it would look ridiculous from the inside. Instead, I wanted to use the window on the side, above the bushes, and have the deck wrap around.

If you have 19" from the window sill to the floor, and if you look at the picture of your house, which most likely has 4" siding reveal and 19" will be almost 5 rows of siding down and that will be the top of your deck floor just above the roofline @ the soffit plus you need a ledger so you might have to scrap the idea going over that roof because there will be no room for a roof to remain.

Unless you get into designing something flat, structural which will act as a roof/deck combination with a needed pitch and make the top out of waterproof membrane something like fiberglass so you can hang out on it and put furniture up there, and even doing that you might end up lowering the ceiling of the room under it if that roof/deck has to be insulated, etc. and that could be costly.

That said, it's hard to say from the picture so it's the only assumption based on what I see, your best bet is to get a contractor out there and have him evaluate everything and tell you right away yes or no.

Good luck.

That part of the house is obviously an addition. If you make this work using your idea you will not be able to re-roof in the future and it will look weird. I think you should plan on re-framing the roof with a "flat" roof that you can access through that window.

Were you able to find anything out from your local area about building codes? We are considering something similar over a garage loft space, (haven't built it yet) but we'd also have to consider flat roof vs sloped roof for snow. Just started digging around for ideas. Would love to know where you are at so far in your project!

Steph, 90% of the time the building department is only concerned about framing, proper ledger attachment, and girder size, etc, in addition, joist size and spacing to support the load, attachment to prevent uplift, snow load (if applicable), flashing, etc.

So when you submit drawings as you would for a deck, you have to add additional details on how it will be attached to the roof providing anchor information, etc.

As an example, if you visit this webpage: https://www.skylifthardware.com/ the manufacturer of this hardware provides load calculations, attachment methods, etc so that information would have to be attached and provided to a building department for a review or if you use an architect, he would use specs from the manufacturer.