Not breaking the rules of the game, but rules on breaking things in the game!
Back in the old days, when I was a little DM, most often we would play Advanced Dungeons and Dragons (1st edition). One of the house rules we tinkered with was equipment damage. When one of the PCs was hit with a 20 (critical), their armor suffered severed damage and needed to be repaired. In the meantime, their damaged armor’s AC worsened by 1 point. It was a houserule that made treks into the dungeons a little more dangerous without major housekeeping of the inventory.
A lot of dice have been thrown under the fridge since then. I came across an excellent posting of item damage here.
Here’s my take on equiptment damage.
Note–this is geared towards White Box rules but should work for any system with little or no modifications. This is an easy switch to Pits and Perils. I will post the notes on this sometime.
Quality of Items
Weapons, armor, and tools all have some degree of quality. They can be categorized into four groups–fine, standard, poor, and broken.
Fine quality items will cost at least 20 times the normal price. They are exceptionally well made.
Fine weapons will give the wielder +1 to hit (non magical). Fine armor will increase movement rate by 10′ per round. Fine tools will give the user a +1 bonus when using them. (I usually roll a d6 to determine if a task is successful. Depending on the circumstances, I come up with an X-in-6 chance of success.)
Standard weapons, armor, and tools are just that. They provide no extra benefits. They are just serviceable items.
Poor weapons cause the wielder -1 to hit and are so bad that a roll of 1 or 2 will indicate it has broken. Poor armor -1 to AC. Poor tools will take twice as long to get the job done.
Broken weapons, armor, and tools does no one any good. They need to be repaired.
Shields can either be fine, standard, or broken. A fine shield can absorb two blows (Shields Shall be Splintered rule) before breaking. The first blow reduces it to a standard shield and the second blow will shatter it. A standard shield can only absorb one blow (Shields Shall be Splintered rule) before breaking.
Loss of Quality
Each time a weapon is damaged, it will lose a level of quality. For example, a fighter swings his fine sword but rolls a 1. A roll of 1 in my game indicates a critical miss and then I need to consult the critical miss table. If the critical miss table indicates the weapon is damaged, the fine sword becomes a standard sword (and loses the +1 to hit benefit that fine weapons are given.) If the sword is damaged again, it will become a poor sword. Any roll of 1 or 2 for a poor weapon indicates it has broken.
Repairing the item can be done if it is taken to someone with smithing skills. Magical spells of mending will also work. Repair of an item will be 10% of original cost for each level of quality that was lost. Example, if a fine sword was damaged twice and is now considered poor condition, it would cost 20% of the original price to restore it to fine quality. No item can be improved to a quality greater than its original quality.