From the 3.5e SRD.
Magic armor or a magic shield must have at least a +1 enhancement bonus to have any of the abilities listed on Table: Armor Special Abilities and Table: Shield Special Abilities.
All of the special abilities with a fixed cost (and all weapon, armour, and shield special abilities full stop) are found in those tables. This is reiterated in a few places (MiC, RC). There are no rules or rulebooks that contradict these rules for special weapon and armour abilities, and to my knowledge, there are no special weapon or armour abilities that have even an exception to this clause.
Due to the utter unambiguity, allowing special abilties to be added to weapons and armour without a +1 enchantment first would be a houserule (although not one i'd personally consider a bad thing).
Nb: If playing purely by RAW, a magical effect or ability (does one even exist?) that removed the +1 bonus from a magical weapon or armour would also remove any special abilities that armour or weapon had. Technically, I believe this would allow a suit of armour or a weapon that when given any spell or effect that gave it a magical enhancement bonus of +1 or greater, to activate special abilities that had been enchanted onto it while consistently under the effect of a +1 or better spell-enhancement, due to previous FAQ answers on the effects of removing (and then reinstating) a prerequisite for an ability.