Ok so we have a unit in a 6 unit block built around 1935. We pulled up the carpet and found original hardwood (actually softwood). We refinished it, but after 5 years there's gaps here and there which traps dirt and boards were starting to fail and wood filler failing where we just decided easiest thing to do was just put down some new laminate flooring (floating floors) over top (I know I hate replacing original, but dust allergies etc, it was the decision we came to. I've installed these plenty of times as builder with no issues and was the simplest option to just go right over the existing 19 mm tongue and groove wood flooring. Mid install I noticed a lot of noise, almost a crackling noise almost everywhere we stepped on the new floating laminate. I had cleaned everything properly and checked for unevenness in the floors as I'm sure that's what everyone will think of first.
I halted the install and started to pull up the existing floor to look at what was underneath. I found that the builders ran many joists on their sides rather than on edge. So I'm thinking there is minor flexing in the floors that we just never noticed. The joists are floating above the concrete slab, in some spots you wouldn't even get a 2 x 4 on edge without having to raise the level of the floor everywhere. I have never seen this before and just seems like building 101 to have joists on edge. Trying to think of my options and hoped someone might have come across this and have advice.
Thinking, extra blocking under the joists - means cutting randoms holes everywhere pulling 1 to 2 pieces up and putting in the blocking.
Pull everything up and raise the levels of the floors and do the framing properly. Issue with this is it means pulling up our newly renovated kitchen cabinets, which isn't really an option.
Do away with the floating floors and go with nailed hardwood in hopes it doesn't make noises when the floor flexes. - hoping this would work because we have no issues with the original floors. Would also save a huge amount of time and effort.
Open to hear any other suggestions... 