The armor cap is about 567, if you have high alteration, you use a shield, and don't have smithing can you use a shield spell to hit the armor cap? (The reason behind this question, is due to attempting to make an experimental shield using heavily armored mage, and I'm curious if maxed out smithing is necessary for the potential of such a character, note that I'm not interested in powerful melee weapons for such a character). Please note, I don't want to spoil for myself what all the artifacts or unique armor is in Skyrim, I simply want to know if smithing is a requirement to make a heavily armored character hit the armor cap. Is smithing a must, or is there a work-a-round about this?

Has anyone tried to hit the armor cap without smithing by compensating with alteration shield spells mixed with armor? Does it work? (Posted this in spoilers cause it may be considered a tiny little spoiler).

I'm pretty sure that as long as you have perks in Juggernaut and the bossest armor around you should hit cap. Shield spells and Heavy Armor enchants wouldn't hurt either.

Definitely. You just won't be able to do it as early, and you'll need to spend a few more perks in Heavy Armor. No big deal.

*edit* You wouldn't be able to do it as early, because the best heavy armor won't drop naturally until you're into the higher levels. (in case that wasn't clear)

Also, you might consider using the Lord Stone.

The Alteration master spell "Dragonhide" caps your physical resistance (80%) for up to 2 minutes.

The Alteration expert spell "Ebonyflesh" increases your Armor by 300 for up to 4 minutes if (1) you're only wearing cloth; and (2) you've perked 3/3 Mage Armor. If you wear Armor or don't perk Mage Armor, it only grants 100 Armor.

Without Smithing, you won't be anywhere close to 567 Armor. You'll be better served by wearing cloth and using Mage Armor. Cloth + perked Ebonyflesh + Lord's Stone grants 350 Armor (displayed), which is 54% mitigation, and you can always cast Dragonhide before a boss fight for a short spurt of maximum physical mitigation.

Edit: A full set of Daedric Armor + Shield + 100 Heavy Armor Skill + Ebonyflesh might get your armor capped. I'll have to look into that. I still wouldn't recommend it, as being a one-handed Mage will prevent you from using some forms of magic effectively (namely dual casting Destruction and Illusion), but it's probably viable.

Actually I've found the key to be, to keep a shield out when not in combat just in case your character gets ambushed, and to begin combat with melee enemies either opening up with a two handed cast, or charging right into their faces, shield block stunning them, then finishing them off with multiple two handed casts. The key to the idea is always having a shield out when not casting, opening up with a shield bash depending on the situation or if ambushed/in a tight corner, then letting out the chain casts. Another part of this build idea, is specing for 5/5 in one handed, and stamina cost reduction for one handed abilities along with blocking, so the character can switch between a (decent but not great) dual wielder, or a decent sword-and-board type when out of magicka or depending on the situation. One handed spells in general seem just too weak to rely upon all the time, it's really just about switching between a shield, dual weilding, and two handed destruction attacks depending on the situation. Perhaps using a bow later on as well.

The idea is to have a caster that doesn't share the debilitating weakness most casters have of getting ambushed by melee, is hard to kill with physical damage in spite of not having particularly high hp, and who does decent but not great melee damage when out of magicka. The weakness of the build being fighting other casters, only being good with destruction magic, having relatively poor melee abilities, low mobility, and no ability to sneak. To my pleasant surprise though, I recently discovered that the player can get more maximum perk points than I thought, so getting rid of smithing doesn't seem so necessary anymore.

100 Heavy Armor + Full Daedric Armor (No shield) + 5/5 Juggernaut + Well Fitted + Matching Set + Ebonyflesh = 78% DR

Letra ought to sink two points into Smithing for Elven and 3 into Light Armor (1/5 Agile Defender, Custom Fit, Matching Set) to be armor capped (without a Shield) in a set that weighs 7 lbs total.