Can someone please help? I spent a fortune 8 months ago on a solid oak floor laid in a living room and dining room. The floor is laid over weyroc, the sub floor is soil/ rubble. The floor has expanded with each board cupping up to 4mm over a 150mm width. I've also laid a loose offcut on top of the floor and this has gone the same way. The problem is likely due to high humidity, not sure if its coming from the sub floor and whether or not a damp proof membrane will help? The floor is discrete nailed not floating. I’m trying to sort the problem before sprog #2 arrives in a few weeks!