Additional Reinforcement Needed For 1/2" Subfloor?

[jamesmiller]

Hello,

I will soon be installing 1-1/2" wide 3/4" thick solid oak strip flooring in my kitchen to match the rest of the main floor of my 1963 rambler here in Minnesota. Previously, the kitchen flooring was thin carpet over 3/4" plywood.

Like the rest of the flooring, these boards will be laid perpendicular to the solid wood joists. Another key detail is that the subfloor is 1/2" plywood (and not tongue-and-groove).

The original oak flooring elsewhere in the house was nailed primarily to the joists, so only about every 16". I will be using cleats (much flimsier than the current nails, but maybe with some additional holding power due to the 'ribbing') and could certainly do the same, but I've heard that people nowadays prefer to nail every 6-8" or so. The existing flooring is in real good shape, just some minor gaps here and there in the winter.

The subfloor has some deflection at seams between the joists, so I plan to at least install solid blocking between the joists to address this. I will also take the common measure of screwing down the subfloor to reduce squeaking.

However, what I'm wondering about is whether nailing between joists into 1/2" plywood, that being so thin, will help much, or if I should beef up the subfloor from below (between the joists, glued to the underside of the subfloor) with some additional plywood where I can. What do ya'll recommend here?

1. Should I thicken my subfloor by adding plywood from below?
   1. If so, what thickness would be good without getting excessive?
2. Should I still nail every 6-8"?

Any additional considerations are appreciated as well. Thank you to everyone in advance!

 

[Incognito]

If the 3/4" strip is working out since 1963 on the 1/2" ply subfloor nailed to the joists why would you worry about/consider changing this design for the kitchen transition?

 

[jamesmiller]

If the 3/4" strip is working out since 1963 on the 1/2" ply subfloor nailed to the joists why would you worry about/consider changing this design for the kitchen transition?

The only thing I'll be changing with the flooring itself is the fasteners. The old, beefy nails were pounded in by hand, and the new fasteners are what works with my pneumatic floor nailer. They're cleats, which are much thinner than the old nails. Similar width.

I do tend to overthink things like this, so maybe the cleats will be just fine if used every 16". I've just seen so many recommendations to nail more frequently than that, so I'm trying to reconcile those guidelines with the quality of the old floor considering the change in fastener type.

 

[JPfloor]

Thickening the subfloor from below? That’s a new one on me. I wouldn’t try that. I would still nail it every 6 to 8 inches. Just use the shorter cleats.

 

[Incognito]

The only thing I'll be changing with the flooring itself is the fasteners. The old, beefy nails were pounded in by hand, and the new fasteners are what works with my pneumatic floor nailer. They're cleats, which are much thinner than the old nails. Similar width.

I do tend to overthink things like this, so maybe the cleats will be just fine if used every 16". I've just seen so many recommendations to nail more frequently than that, so I'm trying to reconcile those guidelines with the quality of the old floor considering the change in fastener type.

I doubt I would want to change the fastener system given the success of the existing installation. That's just me------especially if it was MY house.

 

[jamesmiller]

Thickening the subfloor from below? That’s a new one on me. I wouldn’t try that. I would still nail it every 6 to 8 inches. Just use the shorter cleats.

Haha, I figured it wouldn't be something people would recommend—haven't seen or heard of anyone doing it, but thought I'd ask just in case it was deemed reasonable enough. 6-8 inch spacing does sound appealing as I have seen it being recommended all over the place.

I doubt I would want to change the fastener system given the success of the existing installation. That's just me------especially if it was MY house.

I tried to keep my description pretty brief while providing all the details, but I didn't mention that the existing floor installation is not perfect and I would like to do better. Some squeaking (subfloor nailed not screwed) and shifting (what sounds like tongue-and-groove movement) in addition to the occasional minor gapping I mentioned. I have also laced/patched some areas where I removed some closets to favorable results, at least for now and hopefully in the long term. Currently, walking on those areas is the most silent in the house, which I'd guess is due to both the holding power of the cleats as well as screwing down the subfloor. Installed them a couple months back.

But, I did those two areas more indiscriminately and used 1-3/4" cleats (what I had on-hand) every 6-8", thus blowing 1/2" past the subfloor (I measured)...

Going forwards, combining advice I've received, I'm thinking of going with the additional hassle of using two nailers loaded with 2 different cleat lengths. 2" for nailing into the joists and 1-1/4" for nailing between the joists. I've seen similar questions on different forums where people advise nailing into the joists AND in between, so I figure doing so as well as using the proper cleat length for each application shouldn't hurt. Maybe only a slight benefit, but oh well. It'll be a nice dancing lesson for me and my lovely helper.

Unless people have definitely seen long-term success just with the short cleats...

 

[jamesmiller]

Update in case anyone stumbles across this thread: we proceeded as described right after my last post here, and the floor is holding up great—holding together tight through changing seasons, no squeaks (likely mainly due to stabilizing the subfloor joints with some additional blocking underneath) etc.

Switching between two nailers slowed down the installation process quite a bit, but we were prepared for it not to be a quick process.

 

[highup]

That's great to hear. Taking the time to do it right does take a lot more time... and money, but when it all turns out nice its very rewarding. Give yourself a pat on the back of you haven't already.
Thanks for reporting back. That makes it rewarding to those here that gave advise..