Knowing what thickness of plywood to use for an attic floor is important if you’re planning to make active use of your attic. This goes double if you plan on doing a loft conversion in the near future. While you will probably upgrade your floor to match the requirements of the conversion project, it’s still important to start with a good base that you can build on easily.
In general, you should use 3/4-inch plywood for your attic floor. This provides a good balance between durability and load on the ceiling joists. Using thicker plywood will put extra strain on your house and might lead to structural problems, even though the plywood itself will be more durable.
You can also use 1/2-inch plywood if you want to lessen the load even further. Keep in mind that this is not suitable in some cases. For example, if your joists are spaced too far apart, the plywood will sag between them. Make sure to not store anything inside your unboarded loft to not damage the foundation and cause it to sag.
Plywood that thin might even be dangerous to walk over. Always make sure to do some load tests to verify that your current setup makes sense. Consult an expert who can guide you through the process before committing to a specific thickness.Loft