Need some of advice on a remodel...

[John L]

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.

 

[JPfloor]

Screwed and glued will work just fine.

I’d rather see two layers of 3/4” when going parallel. No need for AC grade when nailing down 3/4” hardwood… CDX will suffice.

Bridging and sistering can’t hurt but might be considered overkill if you go with the double layer 3/4”.

I’ve used liquid nails sub floor adhesive with no problems. Is it the best? I dunno but it worked for me.

As for a moisture meter I’m not sure which brand is best but for wood I’d go with a pin meter over the pinless. Make sure the batteries are in good shape to get an accurate reading.

 

[John L]

Thanks for your feedback, JP. I would go with a 2nd layer of 3/4" but the additional height would make it difficult to merge with the existing hardwood in the adjacent rooms without adding a transition. I was hoping that the bridging and sistering would allow for an underlayment of 3/8" on top of the 3/4"... but hoping won't change the laws of physics.

 

[JPfloor]

I was hoping that the bridging and sistering would allow for an underlayment of 3/8" on top of the 3/4"...

I’ve never tried that or seen it done but it sounds feasible. I’m not an engineer but if properly done narrowing the distance between the joists and adding bridges should certainly reduce the flex.

 

[Dan]

From NWFA Installation Guidelines:

For double-layer subfloors, the first layer should consist of nominal ¾” (23/32”, 18.3mm) CD Exposure
1 Plywood subfloor panels (CDX), 4’ x 8' sheets or nominal ¾” (23/32”, 18.3mm) OSB Exposure 1
subfloor panels, 4’ x 8’ sheets. The second layer should consist of nominal ½” (15/32”, 11.9mm) CD
Exposure 1 plywood subfloor panels, (Exposure 1) 4’ x 8’ sheets. The ½” plywood should be offset by
½” panels in each direction to the existing subflooring. The panels may also be laid on a diagonal or
perpendicular, with 1/8” spacing between sheets. Nail on a 12” minimum grid pattern, using ringshanked
nails or staples.

I really like my Delmhorst J2000. Self calibrating. Set your species in the meter, then when you take a reading it is what it shows, not to go to a graph to add or subtract.

 

[John L]

Thanks for the input, Dan. I am aware that the NWFA spec is a 2nd layer of 1/2". I was just wondering if 3/8" with 2" x 4" bridging would be stiff enough or is this a potential problem? Again, the 3/8" was to avoid transitions in adjacent room's floor. Any thoughts on clip head ringshanked nails?