  Smooth minimal surfaces of general type with $K^2=1$, $p_g=2$, and $q=0$
constitute a fundamental example in the geography of algebraic surfaces, and
the 28-dimensional moduli space $\mathbf{M}$ of their canonical models admits a
modular compactification $\overline{\mathbf{M}}$ via the minimal model program.
We describe eight new irreducible boundary divisors in such compactification
parametrizing reducible stable surfaces. Additionally, we study the relation
with the GIT compactification of $\mathbf{M}$ and the Hodge theory of the
degenerate surfaces that the eight divisors parametrize.
