Armor Enhancement vs. Natural Armor Enhancement

[MerlinRedbead]

Does an armor enhancement bonus stack with a natural armor enhancement bonus? We all think it should, we just want the rules to back us up

Obviously, enhancement bonuses to armor don't stack with other armor enhancement bonuses.

FOR:
IF the enhancement bonuses are added to the bonus they modify BEFORE they are added into AC, then it will be treated as a single armor bonus and a single natural armor bonus.
-One train of logic is that these are each different types of bonuses.
-Core states that armor and shield enhancement bonuses stack, so precedence states that natural armor should as well

AGAINST:
IF the enhancement bonuses are added DURING/AFTER the values are added to AC, then there are technically multiple enhancement bonuses being added.
-Core also lists off other modifiers for AC as enhancement, deflection, natural, dodge, and size. It does not distinguish between armor enhancement and natural armor enhancement
-Core explicitly states that armor enhancement bonuses stack with shield enhancement bonuses (see equipment section). Because it is not explicitly stated that armor and natural armor enhancements stack, they do not

Can someone provide a rule that provides more clarity here?

[toastedamphibian]

An enhancement bonus to your armor improves the bonus provided by your armor. An enhancement bonus to your natural armor improves your natural armor.

They are enhancing different things, so the question of "do they stack" is not really the correct question. Find your armor bonus (Typically what is provided by your armor, including any enhancement bonuses.) Find your Shield Bonus. Find your Natural Armor bonus (Including any enhancement bonuses). etc. Then add them all together.

Enhancement bonuses to armor and natural armor affect your AC indirectly, not directly.

[Claxon]

Armor and natural armor are two different things that increase your AC. Each can be enhanced by an enhancement bonus.
They are different sources, and stack.

[SlimGauge]

Your armor class is the SUM of
10 + armor bonus + shield bonus + Dexterity modifier + other modifiers

Other modifiers include
Deflection, Natural Armor, Dodge, others

If your armor is magic, it has an enhancement bonus to its armor bonus (not directly to your overall armor class)
If you shield is magic, it has an enhancement bonus to its shield bonus (not directly to your overall armor class)
If (like most creatures) you do not have natural armor, you have a natural armor bonus of 0, but it could be something else. Lizardfolk, for example, have a natural armor of 1.
If you have an Amulet of Natural Armor, that amulet has an enhancement bonus to the wearers natural armor.

[manufactured] Armor <> Natural Armor.

So if a lizardfolk has a a +2 chainshirt, +3 light shield, and an amulet of natural armor +1 and no dexterity modifier

10 + (4 + 2) + (1 + 3) + 0 + (1 + 1) => 22
The chainshirts enhancement bonus has enhanced the chainshirts stock armor bonus of 4 to 6; the total armor bonus of 6 adds to ac
The shields enhancement bonus has enhanced the shields shield bonus from 1 to 4; the 4 total shield bonus adds to AC
The lizardfolks natural armor bonus of 1 is enhanced by an additional 1 by the amulet of natural armor; the total natural armor bonus of 2 adds to AC.

Stated another way, there is no enhancement bonus directly to AC, the various enhancement bonuses increase the existing bonus of something, usually [manufactured] armor, a shield, or natural armor.