Underlayment questions and clarifications

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  #1  
Old 11-02-16, 10:51 PM
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Question Underlayment questions and clarifications

Hi,
I've been doing some research trying to figure out how to secure a 11/32" plywood sheet to 1000sqft of sub-floor in order to glue down my engineered hickory. My flooring salesman suggested screws so I went and bought a box of 2" decking screws (I've seen recommendations for ring shank nails, and staples also but I liked the idea of screws). The sub-floor is really squeaky is some places so...

My questions are:
How far apart should the screws be?

Should I secure the underlayment to the joists, or screw down sub-floor first and avoid joists for underlayment?

Do I need to pre-drill holes, or counter sink screw heads? Or does it not matter as long as it's flush / slightly below panel surface.


Thanks!
 
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Old 11-03-16, 02:57 AM
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Welcome to the forums! We don't know what your subfloor consists of, so our information will be based on a substantially flat (at least 3/4") subfloor material. Definitely secure the subflooring to the joists with 2" decking screws to help eliminate squeaks. I would use the same screws for your underlayment (although I would recommend 1/2") and intentionally miss the joists with the 6" center application of the screws. No predrilling as the screws will countersink themselves. I would use an impact driver for this as it makes it much easier than a drill.
 
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Old 11-03-16, 08:55 AM
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Thanks for the advice!
I haven't pulled up any part of the sub-floor to see how thick it is. The house was built in 1965 and I honestly can't even tell if it's plywood or some other type of material (not OSB). There are definitely some high/low spots and flexing boards.
I get why you recommended 1/2" screws if I'm not securing the underlayment to the joists, is there any harm in using what I have for now and going to 1/2" later?
 
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Old 11-03-16, 04:50 PM
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1/2" Plywood, 1 1/2 to 2" screws. Sorry for the confusion. Hopefully you don't have particle board. It would all have to come out. Look in a floor register to see the thickness and type of wood and let us know.
 
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Old 11-03-16, 05:28 PM
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Thanks for the clarification. After sanding through the layers of paint and dust it looks like 1/2 to 3/4" plywood so good to go. Thanks again for the advice.
 
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