This is a great topic that I have experience often.
Quite by accident, I discovered Clove Bud Essential Oil.
This natural product not only kills black mold, but also the spores!!! I did research, and it's true.
I sit on my porch often, and the porch side of the house faces North. Very little sun in summer, a few hours at most, and no sun beginning in the fall and winter. I also live in SE Pennsylvania and it is a high humidity zone.
Snow would accumulate on the ply wood which isn't graded correctly, so when it the snow melts, or rain happens, it just puddles on the edge. This also happens on the edge of the tin siding....it's a condo community, so if I mention black mold, they are going to tackle it with toxic goo.
I am sensitive to black mold, and hated the smell, so when the snow began to melt, and the black mold smell was intolerable, I grabbed a little bottle of Clove Bud Essential Oil and dripped several drops into the melting water (small porch) . The clove oil sure smells better than the mold! After about 10 minutes, I wanted to sweep off the snow to avoid pudding, low and behold! The black mold lifted right off! Easy as Pie!!! That's when I ran to my computer to research it more, as I am an Aromatherapist. Wow! It won't harm my out door plants, it is not toxic to humans.
I place it full strength on the plywood to let it seep in for 10 Minutes and sweep around to get all the effected areas, then rinse off.
I cleaned my whole porch with a small bucket of water, a solution of 2oz 7th Generation Laundry detergent, to 30-40 drops of Clove Bud Essential Oil (mix that together first before putting in water) omigawd! No mold, spores, or bad smells!!!
I put a few drop in my dish detergent for dishes, a drop or two in the washer for anything smelly, and it smells like the Holidays.
It is NOT expensive, and a little goes a long way.
Clove Bud is a strong smelling oil, and the scent will linger for a little while, but it doesn't bother me, and I have had no problems with it. Use sensibly.