Red oak is generally harder than ash wood. This conclusion is based on the Janka hardness scale, which measures the resistance of wood to indentation. According to the Janka scale, red oak has a hardness rating of approximately 1290 lbf (pounds-force), while ash wood has a rating of around 1190 lbf. This slight difference in hardness makes red oak slightly more durable and suitable for applications requiring higher strength, such as furniture frames and flooring.

The Janka hardness test involves measuring the force required to embed a 0.444-inch steel ball halfway into a wood sample. The higher the force required, the harder the wood. The data from the Janka hardness scale indicates that red oak is slightly harder than ash, making it a preferred choice for applications where durability and strength are crucial. This difference in hardness is due to the wood's cellular structure and composition. Red oak has a denser grain and a higher proportion of hardwood fibers, contributing to its greater hardness. Additionally, the presence of silica in red oak can further enhance its hardness and resistance to wear and tear.