I am adding 500 ft of 3/4 over 1/2 in plywood. I know that I am pushing the subfloor thickness but the rest of the house has 3/4 oak over the same subfloor. If I change the subfloor I will have a height problem where new floor meets the old floor. Will I be ok if I use 2" staples and hit all the floor joists. My question is will hitting the floor joists give additional holding power?

Darryl

I am sure that I can hit the floor joists because the subfloor has chauk lines and I am installing across the joists. The subfoor seems to be in great shape as it was very hard getting the ring shank nails out when I removed the partical board under the carpet.

Thanks

No.. How can you always hit floor joists?

1/2" sub-floor, not 5/8" as required by NWFA/NOFMA? What is underneath that? The floor Joists? How far apart?
Are you sure?

In the old post WWI houses that were put up in the Northeast (like my house), 3/4th tongue and groove hardwoods would be put down directly on the joists (no subfloor what-so-ever). Mine are fine after 80 years...but i sure as heck would not reccomend it!

Nick

NOFMA says the minimum acceptable thickness of a plywood subfloor is 5/8" going over joists 16" OC. If your joists were closer, say 12" OC, then the 1/2" plywood would acceptable, IMO. Your 2" fasteners will penetrate through the 1/2" subfloor so marking out the joist locations on your felt paper and attempting to hit those AND in between ( fastener nailing schedule: every 8" )
will be your best bet. I think you shall be OK.

You need to keep in mind that most 1/2" subfloors are not T&G... that fact alone makes a considerable difference. I have looked at many repair jobs where particle board UL was removed and solid hardwood installed directly over the 1/2" CDX plywood sheathing subfloor. Gaps galore , squeaking... no fixing that, just band aiding.

Like Gary said, hitting the joist is highly recommended if you proceed. If a reader has a 3/4 " thick subfloor... trying to hit the joist when blind nailing is a futile effort... the fasteners will only kiss it.

Jerry, I agree. I would normally recommend adding more plywood but this person already has 3/4" hardwood installed elsewhere that he is trying to match up to. So in this scenario, we have to decide between the least of two "evils". If the 1/2" plywood subfloor/sheathing is not tongue and grooved together, it could be a good idea to go under the house and add blocking at every plywood seam to support those seams and prevent squeeking. About attempting to nail to the joists. This is the ONLY time it makes a difference. When the subfloor is this thin, 1/2", there's not much for the staple to grab to so the installer is better off nailing at the joist locations. And as you stated, over 3/4", it would NOT matter.

Since I have a couple of things working against me. Subfloor to thin and not T&G. Would it help if I glue the plywood seams? I could use either a construction glue or Gorillia glue. I do need to replace some subfloor that appears weak. I could block all the areas that I repalce and I could get to some of the floor from below but about half is over my workshop with a finished ceilingI am looking at buying a Bostitch MIIIFS 1-1/2-Inch to 2-Inch Pnuematic Flooring Stapler. Is there only one 2" staple availiavle for this model? Do I need to worry about getting the wrong staple.

Thank you for your help. I could not do it without you.

Darryl

Glue the plywood seams? No.
Glue the plywood to the Joists? Yes, and nail.

How far apart are the joists?

Over the workshop? What size are the joists and how far apart are they?
I would think this is the key to any help you could be given.

The floor joists are 2X10 on 16 inch centers. My purpose in glueing the seams would not be not to glue the seams together but to get enought glue in the plywood to joist connection to help firm up the subfloor. Anywhere I remove plywood I would install additional support but on seams that are ok now I would just add glue. Maybe just tilebond III. It is very runny and might seep into the contact area.

Thanks, Darryl

16" centers??
1/2" ply.??

does this floor have to meet with other floors and that is why you cannot add another 1/2" layer?

The old homes here, that have wood directly over the joists, is not 3/4", It is old 33/32 flooring.

I understand the situation you're in Darryl. What I would do is block everywhere i could get to. Then re-nail the subfloor again. Any soft spots in the 1/2" CDX plywood ought to be replaced with new plywood. Try to hit the joist when fastening the floor and probably no more than 6" OC, stay off the ends just a bit more if they are between joist.

Make sure the subfloor seams are sanded and its overall as flat as you can reasonably get it.

(stay off the ends just a bit more if they are between joist.) >>

I was thinking of nailing both sides where ends join if between joists and maybe even nailing the tounge on the end. Is the risk of splitting to high? How about using glue on end joints only? It seems the greatest risk of movement is at the ends when meeting halfway between joists.

Thanks, Darryl

Oh My...
You need to get a pro to do this job.
Stop trying to save money. You may end up costing yourself thousands of dollars.

I have learned alot with your help. I still need answers to some questions.

I am switching from nails to staples baised on infomation on this site.

Is there a risk of splitting if stapleing too close to ends? What is the recommend distance from ends? I seems like putting staples in the end tounge would be safe. Is there a reason not to do that.

Are there different 2" staples for Stanley-Bostitch M111 FS?

I have installed wood floors and have good woodworking skills, just never with these issues.

Thanks, Darryl