What diameter lag screws are often specified for attaching pull-down stairs to the ceiling framing?

The 1/4 inch diameter lag screws are commonly specified for attaching pull-down stairs to the ceiling framing because they provide a balance between strength and ease of installation. This size is sufficiently robust to securely hold the weight and maintain stability when the stairs are in use.

Using a lag screw of this diameter ensures that the pull-down mechanism can handle repeated use without the risk of loosening or pulling away from the framing, which could lead to safety hazards. Larger screws, like 1/2 inch, might be overkill and can make installation more challenging, as they require larger pre-drilled holes and may not be necessary for the loads involved with pull-down stairs. Similarly, smaller sizes, such as 1/8 inch or 1/4 inch, do not provide the necessary strength and could result in inadequate support. Therefore, the choice of 1/4 inch strikes a practical balance for this application.