Armor as temporary hit points

[Sunseeker]

Armor as AC represents a reduction in the statistical probability of taking damage. A character with 4 HP could have high enough probability reduction to stay alive longer than someone with lots of HP and little probability reduction.

Armor as Temp HP just serves to create a larger buffer zone between a PC and death.

In short: Armor as AC increases the possibility that you will live. Armor as THP only increases the amount of time required to kill you.

It might be interesting in a system that does not require rolls to hit.

 

[LordEntrails]

Doesn't work for me conceptually. After you use all your armor HP in a fight the armor falls off of you? You're saying ti's still there, but just ineffective.... and you can repair in in 5 minutes or an hour?

A suit a plate goes from ineffective to perfect in one hour... yea, no.

You don't take any damage if you are wearing armor until that armor is completely useless? Nope, doesn't work for me.

What problem are you trying to solve? Or do you just want to create something new because you can?

 

[Jacob Lewis]

If it has hit points, we can kill it. How much gold and xp can we get for slaying chainmail?

 

[Kurotowa]

Before you start messing with one of the core most elements of the game engine, ask yourself if you've got a specific mechanical result you're seeking to achieve or if you're just tinkering for the sake of putting your own stamp on it. Because if it's the latter, better to start with something simple that won't bork the entire system if you break it.

What does Armor as THP do to all the other game elements that benefit attack roles? What does it do to the value of those feats that trade attack for damage? What does it do to the lethality of monsters built to innately have low accuracy and high damage? How does armor THP interact with healing from spells and HD? What incentives does it create for the PCs to cut the adventuring day short when they've used up their armor THP?

These are just the very first questions you have to have good answers for if you want to mess with something as central as armor AC. I'm not saying house rules are a bad thing, but I've seem a lot of hastily implemented house rules that were change solely for the sake of change and caused nothing but chaos and game imbalance. A game engine is properly named; you can't just swap out the sparkplugs for LED lights because they're bright and colorful and expect it to keep working.

 

[Ranthalan]

I like the direction you're going, but not the method. For me, the goal is to model armor damage and degradation of armor over time (if not repaired). With the idea that HP are not meat points, but represent the PC's ability to withstand damage and use their armor to best advantage, it makes sense to me that if a PC has reached 0 HP, they've used up the effectiveness of their armor and it is now effectively destroyed. But that's not slow degradation. To model that, I think the armor itself could have a sort of HP. The following is a 1st pass:

Armor will have a number of HP equal to its AC value (e.g. leather 11 HP, Plate 18 HP). Armor will lose 1 HP for every encounter in which the PC takes damage that isn't psychic, poison, or necrotic damage. The armor would also lost 1 HP for every critical hit received. when the armor is reduced to 0 HP, it loses 1 AC value of effectiveness. So plate armor would become AC 17, and reset to 17 HP. Once armor drops below AC 11, it is destroyed. As the DM, I'll be keeping track of these values, although the player can do so too, if they wish.

Armor that has not lost any points of effectiveness can be repaired by an appropriate artisan for 1/10th the original cost. This resets the Armor's HP. Armor that has suffered degradation can be repaired to its original state for a cost determined by the following formula: original price / (current AC value - 9). Yes, that's a bit cumbersome but yields the following table:

[TABLE="width: 500, align: center"]
[TR]
[TD="align: center"][/TD]
[TD="colspan: 8, align: center"]Current AC Value[/TD]
[/TR]
[TR]
[TD][/TD]
[TD="align: center"]11[/TD]
[TD="align: center"]12[/TD]
[TD="align: center"]13[/TD]
[TD="align: center"]14[/TD]
[TD="align: center"]15[/TD]
[TD="align: center"]16[/TD]
[TD="align: center"]17[/TD]
[TD="align: center"]18[/TD]
[/TR]
[TR="bgcolor: #C6E0B4"]
[TD]Padded[/TD]
[TD="align: center"]5 sp[/TD]
[TD="align: center"]-[/TD]
[TD="align: center"]-[/TD]
[TD="align: center"]-[/TD]
[TD="align: center"]-[/TD]
[TD="align: center"]-[/TD]
[TD="align: center"]-[/TD]
[TD="align: center"]-[/TD]
[/TR]
[TR]
[TD]Leather[/TD]
[TD="align: center"]1[/TD]
[TD="align: center"]-[/TD]
[TD="align: center"]-[/TD]
[TD="align: center"]-[/TD]
[TD="align: center"]-[/TD]
[TD="align: center"]-[/TD]
[TD="align: center"]-[/TD]
[TD="align: center"]-[/TD]
[/TR]
[TR="bgcolor: #C6E0B4"]
[TD]Studded Leather[/TD]
[TD="align: center"]23[/TD]
[TD="align: center"]5[/TD]
[TD="align: center"]-[/TD]
[TD="align: center"]-[/TD]
[TD="align: center"]-[/TD]
[TD="align: center"]-[/TD]
[TD="align: center"]-[/TD]
[TD="align: center"]-[/TD]
[/TR]
[TR]
[TD]Hide[/TD]
[TD="align: center"]5[/TD]
[TD="align: center"]1[/TD]
[TD="align: center"]-[/TD]
[TD="align: center"]-[/TD]
[TD="align: center"]-[/TD]
[TD="align: center"]-[/TD]
[TD="align: center"]-[/TD]
[TD="align: center"]-[/TD]
[/TR]
[TR="bgcolor: #C6E0B4"]
[TD]Chain Shirt[/TD]
[TD="align: center"]25[/TD]
[TD="align: center"]17[/TD]
[TD="align: center"]5[/TD]
[TD="align: center"]-[/TD]
[TD="align: center"]-[/TD]
[TD="align: center"]-[/TD]
[TD="align: center"]-[/TD]
[TD="align: center"]-[/TD]
[/TR]
[TR]
[TD]Scale Mail[/TD]
[TD="align: center"]25[/TD]
[TD="align: center"]17[/TD]
[TD="align: center"]13[/TD]
[TD="align: center"]5[/TD]
[TD="align: center"]-[/TD]
[TD="align: center"]-[/TD]
[TD="align: center"]-[/TD]
[TD="align: center"]-[/TD]
[/TR]
[TR="bgcolor: #C6E0B4"]
[TD]Breastplate[/TD]
[TD="align: center"]200[/TD]
[TD="align: center"]134[/TD]
[TD="align: center"]100[/TD]
[TD="align: center"]40[/TD]
[TD="align: center"]-[/TD]
[TD="align: center"]-[/TD]
[TD="align: center"]-[/TD]
[TD="align: center"]-[/TD]
[/TR]
[TR]
[TD]Half Plate[/TD]
[TD="align: center"]375[/TD]
[TD="align: center"]250[/TD]
[TD="align: center"]188[/TD]
[TD="align: center"]150[/TD]
[TD="align: center"]75[/TD]
[TD="align: center"]-[/TD]
[TD="align: center"]-[/TD]
[TD="align: center"]-[/TD]
[/TR]
[TR="bgcolor: #C6E0B4"]
[TD]Ring Mail[/TD]
[TD="align: center"]15[/TD]
[TD="align: center"]10[/TD]
[TD="align: center"]8[/TD]
[TD="align: center"]3[/TD]
[TD="align: center"]-[/TD]
[TD="align: center"]-[/TD]
[TD="align: center"]-[/TD]
[TD="align: center"]-[/TD]
[/TR]
[TR]
[TD]Chain Mail[/TD]
[TD="align: center"]38[/TD]
[TD="align: center"]25[/TD]
[TD="align: center"]19[/TD]
[TD="align: center"]15[/TD]
[TD="align: center"]13[/TD]
[TD="align: center"]8[/TD]
[TD="align: center"]-[/TD]
[TD="align: center"]-[/TD]
[/TR]
[TR="bgcolor: #C6E0B4"]
[TD]Splint[/TD]
[TD="align: center"]100[/TD]
[TD="align: center"]67[/TD]
[TD="align: center"]50[/TD]
[TD="align: center"]40[/TD]
[TD="align: center"]34[/TD]
[TD="align: center"]29[/TD]
[TD="align: center"]20[/TD]
[TD="align: center"]-[/TD]
[/TR]
[TR]
[TD]Plate[/TD]
[TD="align: center"]750[/TD]
[TD="align: center"]500[/TD]
[TD="align: center"]375[/TD]
[TD="align: center"]300[/TD]
[TD="align: center"]250[/TD]
[TD="align: center"]215[/TD]
[TD="align: center"]188[/TD]
[TD="align: center"]150[/TD]
[/TR]
[TR="bgcolor: #C6E0B4"]
[TD]Shield[/TD]
[TD="align: center"]5[/TD]
[TD="align: center"]1[/TD]
[TD="align: center"]-[/TD]
[TD="align: center"]-[/TD]
[TD="align: center"]-[/TD]
[TD="align: center"]-[/TD]
[TD="align: center"]-[/TD]
[TD="align: center"]-[/TD]
[/TR]
[/TABLE]

I think this does a decent job of scaling the durability between light and heavy armors. I'm a little concerned it might be too tough on leather armor, which would average about 10 encounters. On the other hand, it might create incentive to act judiciously during combat.

 

[AmerginLiath]

What problem are you trying to solve? Do you think armor (especially heavy armor) should be made of tinfoil? Historically high quality plate armor could withstand many, many hits before needing significant repair. It's why people fought with heavy bludgeoning weapons or put spiky bits on their weapons to find the tiny gaps in the armor. But from everything I've read the best way to take out someone in heavy armor was to pull them to the ground and take bits of armor off or simply bludgeon them to death.

I understand the desire to have armor absorb some of the damage, but it seems like that would be better served by some level of DR that can never absorb all damage. So plate armor may absorb 80% of the damage, minimum of 1 point of damage. But to be realistic, bludgeoning damage should do slightly more.

Of course as others have pointed out that has all sorts of other impacts on the game, from how many HP should a PC have to effect on builds that don't rely on armor. In addition, what do you do for monsters or characters that have natural armor? Rely on dex or being incorporeal, etc?

AC (and HP) are probably the worst possible option except for all other systems. It works reasonably well with the rest of D&D design, I don't understand the need to "fix" something that isn't that broken. I can think of all sorts of alternatives, that doesn't make them "better".

I agree with the logic here. There’s also the simple consistency. AC is simply a difficulty class to hit (or to represent a hit that does damage); the d20 DC system indeed is built out of the AC system (once it was flipped from the original naval war game descending-AC track to the modern ascending-AC track). Introducing an entirely new system of tracking and qualifying hit difficulty after forty years just introduces a new unnecessary level of granularity (including a repair issue in a game that’s slowly done away with provision-tracking; a reason I dislike PF2’s new shield system).

One also needs to keep in mind that 5e has rebalanced HP and AC as part of its Bounded Accuracy. AC is already far lower and HP decently higher (especially over time) than in previous editions so that characters and monsters can hit each other over a wider range of levels but higher-level creatures will survive better vs. lower-level threats. Reducing out part of current AC and instead increasing HP with that number would result in even swingier battles, as even more hits are recorded across a greater gulf of proficiency variance but it would take even longer to take down either a character or monster (exacerbating one of the issues noted by many as a problematic side effect of Bounded Accuracy instead of solving anything).

If someone wanted to represent an ablative effect of armor, my suggestion instead would be change how magic armor works. Instead of adding further to AC, consider the pluses as DR (but keep the base armor as it’s current AC) and see how that plays out. But the white room debates over Armor as DR or Armor as HP (debates that have raged for decades; consider e.g. that armor providing SDC or MDC to add to HP in Palladium RPGs derives from how Palladium Fantasy in the early 1980s was Kevin Simbieda’s AD&D houserules adapted into his own game system) appear less operative in 5e than even in previous systems.