Yes, you are right: bulkheads of plywood (they started to crack first), lime as filling material with initial moisture approx 20-25% measured. Lime filling is set that the swelling goes in the width of the ship, not the length. See please photos below.   My cellar has: - about 8m² - in winter constantly below 30%, sometimes below 25% (yesterday measured 20% - this is dry like a gunpowder 🙂  ) - in summer constantly higher than 75%, even 80% or 85% humi