I recently bought a duplex (one side). It has one bath and three small bedrooms on the second floor. There was a first floor, single story, 13x13 kitchen addition added in the late 80's with no basement. I'd eventually like to expand above that kitchen addition to add more space to the second floor. The back of the second floor is currently the location of the home's one bathroom and there is one window into a small 10x10 bedroom. I'd like to incorporate that bedroom into the addition and add a master bath (nothing too fancy, average materials... maybe just a stand up shower) to make a master suite. The original second story has a flat roof. The siding shingles on the original house may contain asbestos. There is currently no ductwork in the kitchen, although I've been assured by my home inspector that the ductwork would not be hard to run, and that the heat, AC and hot water systems are more than adequate for the home's current size. I'm thinking it wouldn't be too tricky, especially since the plumbing is already on the second floor, and I'd be adding another bath to the other side of that wall. Then again, there is always tricky stuff when it comes to additions. I know it is nearly impossible to give an estimate without actually seeing the place and knowing how well the kitchen addition could support the second floor. Could you give me a ballpark figure? Thanks!

A good starting number these days is $165 per square. Depending on where you live. And what exactly you are going to have for fixtures trim an so on

Wow! That's Way High Lol. A Brand New Home Say 3200square Ft Will Run You 1.35 To 1.50. And That Is Trimed Out Fairly Nice.

Some Areas Are Higher Than Others, But In Remodeling Going By The Square Ft Really Isn't The Best Way To Go. Least I Can't Price Them That Way.
Only Way I Can Give You A Estimate On That Is To Have The Actual Square Ft You Want To Add And What Will Be In It. What Is The Exterior, Tile Or No Tile. Details Like This Are Important , They Can Change By The $1000.
The Last Bath Addition I Completed Was $35,000, It Was A 12 X 16 Single Story Viynl Siding On The Outside, With A 30' Handycap Ramp With An Exterior Door In The Bathroom. Also, A Laundry Room, 2 Closets, Toilet, Double Vanity , Handycap Shower. Crown , 2 Piece Chairrail, 5 1/4 Base
Nice Wide Casing, The Inside Was Really Trimed Out Nice,
Need More Details For A Better Estimate For Your Bath

You might want to invest in a Architectural Design software program. I use Chief Architect, but they also sell some lower cost versions under the Better Homes & Gardens name brand. Just Google "Chief Architect" and you can check out all the info. What I like is the ability to cost-out the projects in a full spreadsheet manner after creating the final design for any project (whether my own spec-homes or a clients project).