The angle at which a board is cut determines how the finished product looks. Wood flooring is either plainsawn, quartersawn or riftsawn.
Quartersawn flooring is a most ideal choice for installations over radiant floor heating, as recommended by the National Wood Flooring Association.

Riftsawn

Riftsawn is similar to quartersawn, but the cut is made at a slightly different angle.

The hardest wood flooring on this Janka list is not necessarily the best one to purchase. One has to make a decision based on how forgiving a wood flooring is and whether or not it will perform well in the climate you live in.

Quartersawn

Quartersawing produces less board feet per log than plainsawing and is therefore is more expensive. The log is first cut into quarters and then sawn perpendicular to the growth rings. Quartersawn wood twists and cups less, wears more evenly and is more stable. When quartersawn flooring is introduced to changing climates and humidity, the wood expands and contracts vertically instead of horizontal.

The flooring will tend to expand and contract more across the width of the boards.

Plainsawn

Plainsawn is the most common and least expensive method of wood flooring cuts. Plainsawn contains more variation than the other two cuts because grain patterns resulting from the growth rings are more obvious. This is the most economical method because it creates the widest boards with the least amount of waste. Plainsawn is less dimensionally stable.

The Janka (or side) hardness test measures the force required to embed a .444 inch steel ball to half its diameter in wood. This is one of the best measures of the ability of wood species to withstand denting and wear. It is also a good indicator of how hard a species is to saw or nail.

The higher the number the harder the wood