On 10 and 12 wide planks use 3 nails per row.
Face nailing needed for 12 inch wide plank floor.
When installing solid wide plank floors over a plywood subfloor the best method is to apply adhesive to the floorboards blind nail the length of the boards with a pneumatic nailer and face nail when you reach the end of a board.
Installation of wide plank flooring nail down installation of wide plank solid and wide plank engineered flooring requires additional bonding to the subfloor to prevent movement and squeaks.
Regardless if installing a 3 wide engineered hardwood or a 5 wide engineered hardwood plank you are not using any more fasteners despite the increased width.
This is done by introducing glue to the nailing process.
Regardless of how many nails you choose to use per row you are replicating the method of using hand forged nails hundreds of years ago.
Face nail only the last row if it will be.
A 4 wide plank is still begging to be face pegged as i mentioned also in the article.
When stapling nailing down you only have the fastener holding the edge of the board down.
As this prevents the hardwood floor from expanding.
It just depends on how narrow you indoor humidly range is.
Entails using adhesive in addition to nails even if you re installing a solid wide plank floor.
Extremely wide boards 8 to 12 inches wide require three nails instead and boards under 4 inches use one nail.
On 8 wide boards you may choose either 2 or 3 nails per row.
So if all this sounds like too much work just buy the standard 3 1 4 wide t g strip floor and blind nail it simply and easily with the flooring nailer.