Sprinkler Requirements Plymouth, MA

[Connor Tilton]

Good Day Everyone, 

I own a 4 family property in Plymouth, MA.  I have three (2) bedroom apartments and 1 Commercial "store front" unit.  I have filed with the Zoning Board in Plymouth to change the use of the unit from commercial to residential.  The building is zoned transitional commercial currently, so the town requires a special permit to alter the structure...no big deal.  So now that I have the ball rolling, the town is trying to mandate that I install sprinklers in the ENTIRE building which will include a fire alarm system that will need to be monitored, in my terms $40,000 worth or work?!?! 

So I know there used to be something like "if your sprinkler install was more than %15 of the renovation, you were not required to install sprinklers"

Can anyone shed some light on this for me, and maybe cite some building codes articles or point me in the right direction.  

Thank you very much in advance.