Need some of advice on a remodel...

[John L]

Reposting from the Hardwood Floors section to see if I can get additional feedback... Hope that's ok.

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Hey everyone, thanks for taking the time to help. In short, want to make sure I have the sub-floor properly spec'd... I removed old flooring (4 layers - 1 carpet, 3 wood) down to joists in most areas where feasible... there is some remaining 1 x 10 plank sub floor. I need to run the new 3/4 white oak parallel to the joists (yeah, I know) partly for aesthetic, but mostly how it will tie-in to other rest of the original hardwood areas. Fortunately, the additional layer discovered at tear-off will provide some room to add an additional layer to help stiffen the floor for parallel hardwood/joist installation. Please see attached PDF for a rough sketch.
1 - Can I use appropriate screws w/ adhesive to attach 3/4 CDX to joists (#10 GRK, etc.) or do I need to use a ring shank nail? If nail only, can I use clip head nails (I only have a framing nailer that shoots clip head nails.)

2- Adhesive between ⅜” and ¾” layers? Staple or screw 3/8 to 3/4? (e.g. Patriot Timber's Sureply states no adhesive, staple schedule only with their underlayment.)

3 - Bridging good idea or bad? (see PDF)

4 - Sistering good idea or bad? (see PDF)

5 - Any general feedback on moisture meters? Will use primarily for wood projects. Although an occasional lath and plaster scan would be nice. Can you get anything decent for $200- $300?

6- Lastly what's your pref on adhesives for sub-floor? (Bostik, Titelbond, Liquid nails)

Any input is appreciated. Thanks.

 

[C.J.]

I would really like to see 2 layers of 3/4” plywood for subfloor and underlayment if you’re going to be installing hardwood parallel to the joists.

Subfloor adhesive should be used between the joists and the subfloor as well as in the T & G of the subfloor sheets. You are getting 3/4” T & G for your subfloor aren’t you. Screws are just fine for fastening the subfloor. I screwed my subfloor to the joists. Nails will work just as well. Clipped head nails or not I couldn’t tell ya. Are you getting this inspected? If not and clipped head is all you got then clipped head it is.

First layer of plywood is your subfloor, the second layer is an underlayment. No adhesive should be used between the subfloor and the underlayment. The fasteners for your underlayment to the subfloor should not penetrate through the back of the subfloor. 3/4” subfloor and 3/8”? underlayment is 1 1/8”. Good luck finding nails that short for a roofing or framing nailer without special ordering a case. You can easily find that length fastener in staples.

What’s going on with your joists? What is the span of the joists, the spacing between the joists and the dimensions of the joists. Is there currently blocking between the joists?

 

[John L]

I would really like to see 2 layers of 3/4” plywood for subfloor and underlayment if you’re going to be installing hardwood parallel to the joists.

Subfloor adhesive should be used between the joists and the subfloor as well as in the T & G of the subfloor sheets. You are getting 3/4” T & G for your subfloor aren’t you. Screws are just fine for fastening the subfloor. I screwed my subfloor to the joists. Nails will work just as well. Clipped head nails or not I couldn’t tell ya. Are you getting this inspected? If not and clipped head is all you got then clipped head it is.

First layer of plywood is your subfloor, the second layer is an underlayment. No adhesive should be used between the subfloor and the underlayment. The fasteners for your underlayment to the subfloor should not penetrate through the back of the subfloor. 3/4” subfloor and 3/8”? underlayment is 1 1/8”. Good luck finding nails that short for a roofing or framing nailer without special ordering a case. You can easily find that length fastener in staples.

What’s going on with your joists? What is the span of the joists, the spacing between the joists and the dimensions of the joists. Is there currently blocking between the joists?

C.J., Looks like the NWFA spec for parallel installation is a 2nd layer of 1/2" giving a total thickness of 1 1/4". I was just wondering if 3/8" with 2" x 4" bridging would be stiff enough or is this a potential problem (other than the underlayment fastner length)? Joists are 2" x 8", 16"o.c., 12' span bearing-to-bearing. I'm in the process of adding blocking (basically the plywood is supported 16 o.c. by the joists in one direction and supported by blocking 24" o.c. in the other direction. Please see attached PDF. (Ignore the question about adhesive between underlayment and subfloor, as it will not be used.)

 

[JPfloor]

You’re asking if it would be ok to cheat a little on the thickness of the plywood by adding some bridges and sistering up the joists…. Maybe…Probably…Sounds like it should work. I would roll those dice…

 

[C.J.]

3/4” ply would be a normal and adequate thickness for 16” OC joists. For 24” OC joists you really should have 1” of subfloor thickness. Now add to that the fact that you want to run parallel to the joists. That means your subfloor is the only thing keeping your floor from sagging between the joists. We’ve all cheated the odds a little here n there but this is the time and place to pay for an extra 1/8” or 1/4” of thickness.

 

[JPfloor]

3/4” ply would be a normal and adequate thickness for 16” OC joists. For 24” OC joists you really should have 1” of subfloor thickness. Now add to that the fact that you want to run parallel to the joists. That means your subfloor is the only thing keeping your floor from sagging between the joists. We’ve all cheated the odds a little here n there but this is the time and place to pay for an extra 1/8” or 1/4” of thickness.

I think you're mixing up your posts. This guy's joists are 16" OC and he plans on beefing that up and would have 1 1/8th total plywood with the two layers.... The other guy on a different post has 24" OC joists.

 

[C.J.]

Well at least I didn’t run a red light because I was responding to the wrong post.

 

[John L]

Thanks for your help guys... Drive safe!