I have a framing business. Recently, a builder asked if I would screw down the floors when home buyers request that. I told him that I would consider it and get back to him. Since I have never screwed down a floor I have several questions to those that have. We normally frame with 2X10's or I-joist and 3/4" plywood subfloor. Houses range from about 2000 SF to 3000 SF. What screw size is best? Cordless screw gun or corded screw gun? Should we glue and nail as we always do and then screw down the floors later or just use screws? Is glue required when using screws? How much extra do you charge for screwed down floors? What screw spacing works? Is there anything else that I should know about this that I didn't know to ask? Thanks in advance for any and all help with this.