So I bought a house, then decided to install America cherry. After I pulled up the carpet there was particleboard, so I decided to pull up that. Now I have ½ plywood perpendicular to the joists and a layer of 15 pd felt.
I’m going to add some more plywood looking at ½ to ¾ “, that will be installed perpendicular to the first layer of plywood.

Should I nail 2nd layer of plywood on top of the 15 pd felt or remove the felt?
My house it at 65% RH due to basement issues, once I get it down and stabilized at <50% I will add a moisture barrier and nail down cherry. :-)~

Am I screwing anything up?

A 1/2" subfloor is useless.
Do it right, and remove it, spread constrution adhesive on the joist then go over it with 3/4" Advantec T & G subflooring, Just follow the nailing pattern on the panels. Now you with have a rock solid, water resistant none squecking subfloor.
You can then use tar paper or Kraft paper under the hardwood.
Almost no one does finish on site anymore. Use prefinished and you can walk on it the same day, no smell, it will have a harder finish on it then any finished on site finish.

This message has been edited. Last edited by: joecaption,

I agree 1/2" subfloor is useless,,It requires lots of remolding and modifications..

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I was going to add a comment and a helpful link to a great place to get your tires rotated, but I think Joe hit the high points.

Well this easy job of putting in some hardwood floors just got not so easy. So just adding another layer of plywood is not a good option even if I both glued and nailed?

TOM

By getting rid if the 1/2 the floor will be 1/2 lower making it easyer to have it be the same height as the other floors, all that 1/2 is doing is acting like a shim on top of the joist and is adding no strength to the total floor.
The second layer would be what's called underlayment, glue should never be used between the two layers because it can form gaps that will move which will make the floor squeck.
If you use a Tow Kick saw to cut up along the wall and cut between the joist it will come out faster then that partical board did.
It will also allow you to fix any cracked, sagging, undersized floor joist.

OTOH, if the extra height will not cause you any problems then you can add another layer on top of the existing 1/2" without it hurting anything and saving yourself all the removal work. As Joe says, no glue between, but do install a layer of 30# felt on top of the 1/2" before adding the second layer. While you could get by with a second 1/2" layer, I'd go with a 3/4" T&G Advantec on top of the 1/2" as your new subfloor.

I like the idea of keeping the 1/2" flooring and adding some 30pd felt and a 3/4" subfloor on top of it, then another moisture/sound barrier and then the prefinished American Cherry.

If I’m looking at the right stuff 3/4" Advantech is $40 a sheet
I plan on doing the entire ground level floor except the bathrooms and kitchen ~ 900 FT2 so thats another $1000.00 

What are the issues with this course of action?

Height?
Leveling?

Tom

Only tar paper or kraft paper goes under the flooring not between the layers of subflooring.

maybe shop around for your Advantec. Lowe's around here has it for under $30:

http://www.lowes.com/pd_85795-..._rating|1&facetInfo=

Still, you are looking at $800 to $900. Remodeling is expensive, especially if you do it right.

If you screw the Advantec to the existing with screws set about every 6" then you could skip any paper layer in-between. However, if you choose to nail it, I would still have a paper layer just to cut down on the inevitable squeaks.

As mentioned before, one disadvantage is that you will be raising your floor, first with the Advantec and then with the finished flooring. You'll be adding an extra 1-1/2" above the old subfloor.

If there are any low spots on your existing subfloor, then it's easy enough to fill any low spots and then overlay with the Advantec.

ok Do I need the screws to go into the joists or just the 1/4 plywood subfloor?

I'm thinking the joists so I need 2 - 2.5" screws, any recomendations on the type of screw and I want to get a screw gun for this job and use it for all the dry walling im going to need to do ,,, any reomendations???

I hope that was a typo, no such thing as 1/4 subfloor.
No you do not want to screw the new layers to the joist.
You do not want to have any seams lining up with the seams below.
It's going to need to be attached every 4" on the edges and from 6 to 8" in the field.
Go buy a Ryobi impact driver a charger and two batterys.
Not sure where you would "rent" the needed tool to do this job.
If that 1/2" was gone the job would be far faster.

quote:

Ryobi impact driver

yeah typo it is 1/2". ok i remember no seams lining up.

Do i need a spacer against the wall and do the seams on the 3/4 advantec touch or space those also?
what type,length screws should i use?
i was looking at buying the Senco DS300-S4
removing that 1/2 inch and then adding the 3/4 sounds longer then just laying the 3/4. but i do want to do it the right way.

Leave a little space against the wall but not much - 1/8" to 1/4" will do. The Advantec is T&G and is self spacing. Screws should penetrate at least 3/4" into surface below but 1" to 1-1/4" is better. This is one of the down sides to overlaying that 1/2". Normally, you would avoid screwing into the joists if installing a second layer of subfloor but 1/2" is not enough to really hold the additional 3/4" layer unless you screw it into the joists too.

quote:

Senco DS300-S4

That's a whole lot of money for a tool with limited uses.
An impact driver can drive screws, can be used as an impact gun to install or remove nuts and bolts, and can also drill holes.
I own one of those Senco and there nice but I sure would not go out and buy one for just one job.
That 1/2" is doing nothing but acting as a shim on top of the joist and not giving any real support between them.
That's been a pet peve to me for 30 years. I see it all the time, 1/2 then they lay 3/4 on top of it, why?
To me that's backwards.

After looking at some of the issues i might have i am reconsidering removing the 1/2 plywood. So i will need to buy a toe kick saw to cut along the wall, ensure joists are level then glue and screw 3/4 advantec down. Then i am ready for moister barrier and hardwood flooring right?

Northern tool and Harbor Freight sell a cheap one and Home Depot rents on.

I was looking at:
Roberts 17076 10-46 6-Inch Jamb Saw with Case any recomendations?

Wrong saw.
http://www.amazon.com/Blade-To...eywords=Toe+Kick+saw

Great!
Amazon $120
Sears $200
Harbor Freight $69

I'll pick it up today