I think of house-rules and home-brew as separate things.
To me, a house-rule is something like which of the default or optional rules a game presents in its own text you are using (example: my group uses the cleaving rules in the DMG), plus any changes that you have made that don't fall within the home-brew category (example: my group rules that material component needs are entirely covered by having a spell component pouch or spellcasting focus; no expensive or consumed components to track). And I don't stick with games if my list of house-rules for them gets longer than a page or two - I go looking for a game that fits my group's desires better before alterations.
And to me, home-brew is something that adds more options to the game without altering or invalidating any of the default or optional rules present in the game's text (Example: adding new classes, sub-classes, spells, feats, magic items, monsters, and races). I home-brew any time that my players or I want something in the game that isn't already covered, and I could probably fill at least a book if I were to put all those elements together (they usually exist as little notes in a character sheet's margin, or a post-it, or index card).