What this video covers
The clip connects blocked gutters to basement mold, which is a longer chain than most people assume.
Water that cannot leave through the downpipe overflows and pools against the foundation. From there it works through cracks into the basement, so the visible problem appears several floors below the actual fault.
The takeaway
A basement damp problem is often a roofline problem. Before tackling the basement, check that water is actually leaving the building where it is supposed to.
Read the full written guide: How Gutters Prevent Mold.