i have searched and can not find a definite answer to a question alot of newbies ask....i am installing 3/4" over 3/4" OSB. Do i use the 1.5" or the 2" staples? I have heard that i dont want to go all the way through the subfloor or i will lose holding power. So which is it? thank you so much guys,

2 "

NOFMA nailing schedule stipulates that 2" fasteners are to be used for 3/4" solid wood flooring. They also say 5/8" plywood OR 3/4" OSB is the MINIMUM subfloor thickness for solid 3/4" strip and plank flooring. With either of these subfloor thicknesses, the fasteners will protrude through the bottom of the subfloor, though less for the 3/4" OSB. Some say when a fastener "blows through" the bottom, it loses some of it's holding power. This maybe true. However, I will tell you, in 30 years of installing flooring, I have not a had a floor fail because I used 2" fasteners. So, IMO, you may use either. EXCEPTION: If you are installing a solid over plywood over a concrete slab, then you must use a fastener that will not protrude through the bottom of the plywood. Then it is typically a 1&1/2" fastener for a solid over 3/4" plywood over concrete.

The floor ain't going to fail, but as seasonal moisture content gain and loss happens, the fastener that has blown through the subfloor, will be more likely to squeak more then a floor fastened with a fastener that didn't blow through. Even more so when going over OSB.

When installing over plywood, blow-out is not a concern. When installing over OSB, we use a 1 3/4 fastener to avoid concerns about the bottom of the sub-floor and still have full holding power for the fastener. A passing comment, there are a number of reasons we never us staples, always cleats, but that is for another discussion.