Armor Degradation
Armor protects you by absorbing the impact of your opponant's weapon. Over time, this damage will start to destroy the armor. The number the opponant rolls on her attack, and what kind of AC modifiers you have determine what piece of armor gets damaged.
If an attack roll scores lower than would be needed for a touch attack against you, it misses altogether. The higher the attack roll, the closer the attack came to damaging you. If an attacker rolled high enough to hit you with a touch attack, but failed to overcome your armor bonus, your armor was hit and may have taken damage. Shields are the easiest things to damage, followed by Armor and then Natural armor (if any).
Attacking a Fighter with a Large Shield (+2) and Full Plate (+8 AC) who's Touch AC is 10, a roll result of 1-9 will miss entirely. A result of 10 or 11 will strike ad damage his shield. A result between 12 and 19 will strike and damage his armor. A result of 20 or higher will strike and damage him as per standard combat rules.
Once you've determined the armor affected, it takes the attacks damage minus the armor's hardness in damage. Weapon and Shield Hardness and HP are listed on page 167 of the PHB. When armor is totally depleted of HP, it is broken and becomes useless. Note your armor hardness and HP, as well as the threshold which it protects you, on your character sheet. Why: This is actually a rule that's implied by the cover rules. How close your opponant came to hitting you does indeed determine WHAT your opponant DID hit instead in 3e. All I had to add was the order of priority, the rest of the rule was pretty much there already.Pro: Realism is always a plus. Also, this is much less number-heavy than other similar rules I've seen. It's also based directly off of other 3e rules!Con: Most people just don't care about armor/shield breakage. These people probably don't know how often it happens in real-life sword fighting; but to each their own.
By: Owen O'ConnellImported from a previous version of Planewalker.com You are likely asking the original author, but like you I don't treat Natural Armour in that way, since it is hardened skin, or whatever.
As for the degradation, the armour is still there (as far as I am concerned) just no longer offering any significant defence to blows. Thus you can repair it later (and it would be advisable - much cheaper than a new suit!).
This is a fine system but requires a lot of record keeping and roll checking that will slow down the game play.
Just some feedback
I use a similar house rule which I shall post shortly, it makes the bookkeeping quicker (though less exact) because I originally used an almost identical idea but found that keeping track of the hitpoints was tedious.
You mention natural armor, but there's no way for natural armor to be damaged. It is you.
When armor runs out of hit points and becomes "useless", is it burst into fragments and completely obliterated or is it just unusable until it gets repaired (like in Diablo)?