Legal Bedroom Definition - Worcester, MA

[John Kubilis]

Hello Folks, 

I was wondering if anyone knows where to find the definition of a legal bedroom in Worcester, MA?

I've been searching with no real luck.

I have a half duplex townhouse style unit. Its 2 bed / 1.5 bath on the 2 main floors. There is a basement that I can finish. I'd like to add a legal bed and bath down there to get higher rents and bring the property value up, so that I can refi and get most/all of the money back that I use on the updgrade. 

Most of the basement is below grade. My unit is on the right (pics below). There is a small window.

My plan was to either add a bulkhead entrance or create an escape window. I'd prefer the bulkhead as it has more functionality, but not sure if that would satisfy code to make it a "legal" bedroom.

I am hoping to refinance the property after I make the improvements to get my money back out, but that would definitely require the additional bed and bath to meet code and be considered legal.

If anyone has the answers here, could point me in the right direction of where to find them, or just has any advice in general, I'd really appreciate the help! Thanks!