This has come up periodically before:
For example here: Do Wound Penalties Increase Damage?
Here: Do wound penalties apply to non-combat soak?
And here: Do wound penalties affect soak totals?
My own approach is to apply wound penalties to soak rolls to non-combat damage (including damage from spells), and not even think of it as a House Rule as such (maybe a "House interpretation", with the difference being whether I'm changing a clear Rule or interpreting an ambiguous one - it comes down a bit to exactly how you define an "action").