levelling
Levelling peaks and valleys is required to prevent stress on the locking mechanism of flooring products. Joints are apt to fail if under constant up and down movement as they are not designed to withstand such force. Levelling is also a requirement for product warrantees.
Subfloor Fasteners
It may become necessary, over time, to re-screw sub floors. Older homes may have used common nails and as a result, these tend to allow the planks to move up and down. Modern techniques use screws to eliminate this problem. Ship lap floors in older structures are particularly problematic and do not hold nails very well resulting in squeaks. It is generally best to re-sheet with plywood.
Moisture Testing
It is very important to test moisture content as excessively wet or overly dry subfloors can both be a problem. Damp subfloors cause cupping and warping. An overly dry subfloor cause shrinkage and cracking. Maintaining a year round constant level 40-50{b6ea0089652ad4a58aca5b33b4dc3b9457ef7e7fb33de024b89024463cfe6b66} relative humidity ensures your floor will remain beautiful for years to come.