subfloor attachments

[larrykwiat]

i have a 5/8th inch osb board and a 5/8 inch plywood subfloor in my upstairs bedroom. i am going to screw it in. what size screws are the best. i found some 2 3/4 inch screws at the hardware store that are exactly the same as some subfloor screws that were only 1 1/4 inch. wondering if the 2 3/4 inch screws are to long.

so the floor is 1 1/4 inch and the screws would be 1 1/2 longer.... is that to much?

thanks

[marson]

the rule of thumb I use is that a fastener should be at least twice as long as the material you are fastening is thick, and it should penetrate the wood framing by no less than 1 inch. by that logic 2

1/2" screws would be the minimum, and there is no harm in using some slightly longer.

[M]

I am not an expert but shouldn't you be using under layment flooring nails?