How much superficial damage did combat do to the decks of WWII warships?

By which I mean, all the AA guns, life boats, aerials that sat on deck, how much of that would be wiped out and have to be replaced on a regular basis?

The books of warships that my grandfather gave me always gave the impression that ships had a busy structure outside of the guns and superstructure, most of which looked like it would get blasted away after a bit of a fight.

Or was it the case that ships would come back mostly unscathed or heavily damaged, with nothing in between?

That would all depend.
Type of ship. Who they were in battle with, how many of the emeny were there. How many times they got his and where.

Ship’s crew would do minor repairs, cut away some of the damage. Make temporay repairs. Then repair ships, go to the yards, or even dry dock.

The decks are cleared of personnel during combat except those with specific duties topside. The culminating battle of Guadalcanal involved destroyer-sized to battleship-sized combatants at close range. Short-range, sub-caliber weapons were used, including .50 caliber machine guns, all the way the Hei and Kirishima’s 14-inch guns.

Results? The cruiser Atlanta blew up after taking a 14-inch salvo from the Hei. The cruiser San Francisco lost its front main turrets when they were hit by the Kirishima’s 14 inchers. Then a Japanese destroyer raked it with 5-inch guns, cannon and machine guns. There was a picture of the San Francisco in one of those Ballantine picture books after the battle. It marked the places that received hits from various caliber weapons. The ship looks bent and battered but otherwise still afloat.

And then there was the battleship Hei. It had no American battleship or 8-inch gunned cruiser to worry about that night. But American destroyers were ganging up on it, coming to within 300 feet, raking it with 5-inch, 40mm, 20mm, and .50 calibers. A lot of Japanese sailors were killed, fires started with the potential of reaching the ship’s vitals, and there were some unconfirmed claims of torpedo hits. By morning, it was wallowing at greatly reduced speed, making it easy picking for American bombers.

So it takes all kinds. One salvo from a battleship could blow you out of the water. But some ships can survive hits from a battleship. A battleship’s armor is not proofed against “puny” 5-inch guns. Destroyers and cruisers can pound each other with 5", 6" and 8" guns and results will not be consistent.

Well, going back to the wooden-ship era, a standard order issued in preparation for battle is to secure all loose material on deck that might become projectiles in combat, and to stow all gear not immediately necessary for combat.

During the US Civil War, the ironclad CSS Tennessee was sufficiently armored to endure heavy shellfire, but for some reason her steering chains ran outside the armor and were shot away, along with her flagstaff and various other fixtures. her smokestack was also riddled, which reduced the draft in her engine room fires and lowered her speed.

the quicker-firing guns of WWII could do commensurately more damage. In some cases the damage could be quite extensive without being fatal to the ship’s flotation.

An interesting feature of american battleships was the “all or nothing” armor scheme. The main gun turrets were the raison d’etre of the ship and they plus their ammo supplies were HEAVILY armored. The rest of the ships superstructure was virtually unarmored. The idea is that a heavy armor piercing shell would go right through without detonating. When the South Dakota was dead in the water from an electrical failure and was raked by the battleship Kirishima and a cruiser, this is exactly what happened. She took lots of hits but almost all the big shells went in one side and out the other (through-and-through in naval parlance). This was bad news for the men hit directly by the shell or by shrapnel generated from its impact, but it was much better than if the shell had penetrated armor that was thick enough to detonate it. The result was no loss of seaworthiness and being listed overall as “moderate” damage.

To provide an example of the effect of not using the all or nothing scheme, while the Kirishima was busy pounding on the S. Dakota, the USS Washington snuck up behind her and devasted her with close-range 16" fire. The Kirishima eventually got away but had to be scuttled the next day.

Here’s an article on All or Nothing Armoring.

Here’s an article about a specific hit from the Kirishima on the S. Dakota.

I forgot to mention: the US navy used wooden decks for aircraft carriers in WWII while others used metal decks. This sounds inferior at first, since they’re easier to damage. But wooden decks could be repaired much quicker and easier than metal ones. No (or little) metal cutting needed to clear away the debris and no-to-little welding to put new stuff down.

Example of:

Bomb fragment damage, hangar bay, USS Yorktown:

Depends entirely on the round/shell being used.