Even firing the main armament for a couple of hours could loosen rivets, if what one reads about Rodney is true.
The famous 'badly shaken up' comments come from an American journalist who was onboard and shown the damage to lockers and to the decking. The former were aluminium to save weight, the latter was a less durable wood than on other ships for a similar reason. The lockers did rip of the walls and the deck did splinter under the guns, but whilst visually impressive there was no actual structural damage and Rodney's refit was as expected before the action. There is a piece that mentions this, but as I dont really like citing work I have produced or worked on you may wish to check it elsewhere;
These are the major changes to the gun mountings and were certainly the ones that caused most problems for the designers and for the crews once in service. There were many other changes in the finer details adopted for the "O3" design (Nelson) that have also led to the ships themselves being thought of as sub-standard or badly built. The most notable being the performance of HMS Rodney during the final stages of the Bismarck chase, and relate to the damage she caused to herself due to the blast effects from the main armament.
One of the two most notable defects was the adoption of aluminum alloys for most of the minor ships fittings, such as kit lockers, mess racks, store cupboards and indeed the fittings holding some items in place, especially with regards to the crews lockers and wash facilities. These were all shaken up badly by the main armament being fired, and indeed many became loose and some were even thrown around the cabins and mess decks. Nobody was injured by these unexpected happenings, though many were shocked by the level of destruction that resulted!
The other major fault was the adoption of Douglas fir for the upper deck, instead of the normal teak. This was deemed acceptable by the designers due to the weight saving, even though the resulting loss of appearance and durability were appreciated. However, the fir proved to be less acceptable in service, as it proved to be less resistant to the blast effects from the 16" guns. Indeed, it seems to have surprised many people quite how much the fir was ripped up when the guns were fired over it. This appears to have occurred on all bearings at low elevations, and from "A" and "B" when firing forwards, even at higher elevations. The resulting destruction of the decks was viewed with extreme distaste by some senior officers who wanted the ships to be "tight and tidy" at all times, very similar to the Victorian officers who disliked gunnery practice as it caused soot marks and chipped the paintwork!
Neither of these two faults, though very noticeable caused any loss of fighting efficiency whatsoever! With hindsight, as the ships turned out 1500 tons (Nelson) and 1100 tons (Rodney) under the Treaty restrictions, that some of the measures taken to save weight were adopted at all!
One of the other things noted about Rodney, is that she seemed to wear out quicker than Nelson. This was largely because Nelson was nearly always used to test modifications and new equipment. Rodney was fitted second, as and when/if money could be spared. When WWII broke out, she was already in need of an engine refit. She was destined to never receive this much needed refit throughout the war, despite her extensive service, as she was looked upon as too valuable a unit to spare from duties for any period of time, if she was still capable of service. By the time she could be spared, in 1944, there seemed to be little point in sending her for the refit, as the need for her type had largely passed.
After all, it must take many thousands of tons of water inside the hull to sink a battleship
From memory there was 7,000 tons or so on the Lutzow when she was lost. I will look the figure up and post it later.