I must admit I am kind of allergic to house rules. I don’t like them. I am always skeptical of rules my friends or random strangers have come up with to ‘fix’ an issue they have with a game. I assume that games have been thoroughly researched, tested, play-tested, and tweaked before they ever make it to publication. So the rules as written are written for a reason. That ability or +2 bonus is there because it’s balanced, and changing it even a little bit may have unforeseen consequences down the line. It is like computer coding. How many times has a ‘patch’ to fix one small problem caused a completely unrelated system to crash or fail? (in my line of work… every patch) So I don’t like to ‘patch’ the rules.
That said there are acceptable levels of ‘House Ruling’ I can handle. In RPGs, many people come up with new abilities, items, monsters, even classes. This is fine. RPGs aren’t competitive (or at least not the ones I play) so as long as your homebrewed class isn’t blatantly broken and overpowered that my character never gets a chance to shine then I am good. If the classes available didn’t meet the vision you had for the character you have been dying to play, then by all means house rule it.
Slightly less acceptable, but can be ok, are rules that add systems to games. You want to set the game on a ship, but the sailing combat rules are bare bones, ok I can see you punching them up a bit. However, they better be written out and explained to me beforehand. Also, I need the chance to take skills to improve my ‘rigging’ or ‘cannon aiming’ just like regular combat. Or maybe you want this game to be creepy and horror filled and you want to adapt an ‘insanity’ rule to the game. I can understand that.
The house rules that I take the greatest exception to are ones that change something about the game’s core mechanics. This usually involves bringing another game’s mechanic in a game it wasn’t designed for. How many of you have been in games where Nat 20s inflict double damage or cause you to roll on a crit table while playing a system not written for critical hits? (how well did that work when the enemies rolled a Nat 20 against you?) Another common thing house ruled are character death rules. Death saves, or bleeding out, or other things added to the game not meant to be there. Initiative is another aspect I see house ruled a lot. (I am actually quite guilty of this one because I am such a fan of how Fantasy Flight handles initiative in their Star Wars lines).
The problem I see with these types of house rules is like I said above; changing them has unintended consequences, whether it be game breaking or just changing the feel or play or even player buy-in. Take that initiative issue for example. In FFG’s Star Wars they turn initiative into ‘player slots’ you may make the best initiative roll, but any player can take that slot in the round it’s not just reserved for you. This is great for allowing player coordination but some games have Initiative as its own skill. Why would you spend a lot of advancement points making that initiative skill better, when it’s really not helping define your growth as a character but simply benefits the party as a whole?
So before you house-rule something in your game, you probably should look and see; am I adding something to the game via an ability or a new system, or am I changing a deliberate design decision of the games creator. If the latter, really spend a good hard look at it. Mock test your decision a bit, see if it may break something else. Also talk to your players see what they think. House rules, when implemented, work best as a willing collaboration rather than a dictated mandate.