Non-Conforming Bedroom and Appraised Value

[Tyler Hardy]

Hey Team!

I've got a SFH with a garden-level basement. Currently there is a non-conforming bedroom along with a total of 1,000sqft of livable fully finished and well lit from natural light living space, including a bathroom and laundry — and a kitchenette area. The house is located in a highly sought after area one block North of Old Littleton, Colorado. The house is 1,000sqft above grade, 1,000sqft below grade. Upstairs has 2 bedroom, 1 bath.

My question — a recent appraisal of my home came in far lower than I expected at 455,000.  In doing some home improvements, a neighbor recommended to put  in an egress window for the bedroom in the basement, allowing me to list the house as a full 3 bedroom 2 bath.  

My open question — does anyone have a ballpark range of how much this would increase the value of the home by?

Thanks!