Building a second home on my primary home's lot, will it affect my mortgage?

[Kevin Hausfeld]

Hello BP friends, 

I purchased my primary residence a couple years ago and it is on a double lot. I looked into splitting the lot with my lender, but I dont have the right LTV for them to split it outright without paying down my mortgage with a significant sum I don't have handy. Would it negativly affect my mortgage, or do I need to notify my lender at all to build the second home on the lot and then figure out the lot split later if it's necessary for renting or selling the new or original home?

Thanks for any insight!