A wooden floor made of 40x180 planks laid on beams. The planks have poor geometry, which causes the floor to have large height differences between adjacent planks, irregularities and is generally crooked.
I want to level the whole thing with plywood (already bought – 10 mm) and am considering the following option: screw into the boards with a pitch of 20 cm, so that the heads protrude at the same height, and the heads to lay plywood. Fill the gap between the plywood and boards with a mixture of sawdust and PVA glue or mounting foam. It would be interesting to hear opinions about the practicality of this option.
Screw in self-tapping screws at a distance of 30 cm like lighthouses. Then cut the plywood into 50*50 or 60*60 pieces. A whole sheet will swell 100%.
Apply the plywood glue to the bottom with a padded spatula. Drill holes for the screws on the top of the plywood (25 cm apart) to hide the screw head in the plywood. Self-tapping screws should preferably be galvanized. After 2 days, when the plywood dries, take the sander for plywood and sand 2-3 times, sandpaper grit 40-60-80. The pallet is properly aligned. It is better to use 2 layers of plywood.
P. S. Plywood should be laid with a joint of 5 mm without glue.
If the differences are big, 10 mm foam or PVA will not help.
It is faster and smoother to pour the floor, use self-tapping screws as a lighthouse and use the plywood elsewhere. It is good if you have a level near your house, which is in order. Otherwise, a screed or thresholds are inevitable.