Which of the following is an approved fastener for finish floor underlayment?

The choice of ring groove nails as an approved fastener for finish floor underlayment is based on their design and performance characteristics. Ring groove nails are specifically engineered to provide superior holding power compared to standard smooth-shank nails due to their ridged design, which grips the material securely as the nail is driven into place. This makes them particularly effective for fastening underlayment, as they help prevent movement and shifting that could lead to issues with the final flooring surface.

In contrast, divergent staples might not provide the same level of secure fastening required for underlayment, as they are often used for other purposes, such as securing insulation or in light-duty applications. Cement coated nails, while useful in certain situations, may not deliver the same robust performance as ring groove nails under the stress of foot traffic and load-bearing on finish floors. Therefore, selecting ring groove nails is ideal for ensuring the integrity and stability of the underlayment layer beneath the finished flooring.