Hello!
I am in the process of renovating an old log house and have now opened up the floors. There is a mix of spacing between the joists, ranging from 50 to 100 at the most. The previous floor didn't sway and felt stable. It was solid spruce flooring at 33 mm.
I will be installing a grooved chipboard for underfloor heating, and on top of that, 27 mm solid spruce flooring. That should be able to handle the joist spacing, right?
Best regards