Fastening double subfloor

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Old 12-09-19, 04:50 PM
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Fastening double subfloor

So i have replaced all the joists under my kitchen already.
The subfloor layers seem to be in reasonable condition, but the joists had problems.
Anyway, i now need to attach the subfloor to the joists (2x8s)
Currently the subfloor is made up of 1x8 planks running at 45 degrees across joists, with a layer of plywood above that, below the vinyl sheet flooring which im also replacing.

So my question is if I should, #1 screw down through both the planks and plywood to secure the subfloor to joists, or #2 remove plywood, screw planks down to joists, then screw new plywood to the planks.

From what ive read #2 is preferrable to #1, but #1 would be a lot simpler.

Also, im not sure exactly why #2 is better, but i imagine it has to do with expansion, contraction from temp and humidity.
Any help is appreciated.
 
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Old 12-09-19, 05:03 PM
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Might help to know the thickness of the plywood layer. You replaced all the joists one by one from underneath the subfloor?
 
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Old 12-09-19, 05:22 PM
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And, what were you thinking of adding?
 
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Old 12-09-19, 06:29 PM
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Yes need more info re: the questions above.

Also is the floor now level and smooth?
Was the plank flooring not nailed to the joists?
What are you putting on the new subfloor?
Also what problems did the old joists/floor have?
 
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Old 12-09-19, 07:03 PM
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Looking more closely, the base is probably 1x10s, with it being close to a full 1” thick, and looks to be a 3/8” plywood on top.
I would probably remove the plywood, and screw down the planks, then add 1/2 plywood on top.

There was a lot of rot in the original joists as well as the beam that ran down the middle of the house, so I ended up replacing most of that as well.

I’m not sure what I’m putting on top as finished flooring yet, although I was hoping to do some sort of hardwood.
 
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Old 12-09-19, 07:09 PM
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Yes, you need to remove the plywood in order to put 2 or 3 screws through each diagonal plank. If it's got squeeky nails, this will be your chance to pull them. For best results and to avoid splitting the old wood, you could predrill the holes or get yourself a countersink with a pilot bit.
 
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