Primary Residence Exclusion + 1031 Combo?

[Marcus Mathews]

I am selling my two unit property here in Portland, which is a small 2/1 house along with a detached 1/1 ADU on the back of the lot.

I have lived in the main house for well over two of the last five years, so that definitely qualifies for the primary residence capital gains tax exclusion. My CPA said that the ADU will not be covered though.

My question is: Can I do a 1031 exchange on just the portion of the gain that is apportioned to the ADU?