Fun fact: If your house is under 5 ft of ash, it's not covered by volcano insurance. That only covers you if your home is destroyed by the actual eruption/explosion.
What you need is "pyroclastic event" insurance to cover you for ash and lahar.
/ It cost something like $15/year when I lived in Seattle.
// The macOS spell checker doesn't know "lahar."
This basically covers the financial model of the whole insurance industry;
Getting something like Volcano Insurance requires some specific foresight, I would be slapping myself on the back if my house was covered in volcanic ash right up to the point when I got on the phone to my insurance company to make a claim.