Subfloor

Mischman

An 8 x 16 foot area of my subfloor has to replaced. I have to build it up to 3" total. All the joists are fine and in great shape. To make the subfloor 3" i was going to lay a sheet of 3/4 inch plywood. Then 2x2's over that and then another sheet of 3/4" plywood to give me the 3". There is cross bracing/blocking on the joists at the very edge of where the subfloor has to be replaced. Im using screws for everything instead of nails.


My questions are:
Is this alright to do?
What direction should i lay the first sheet of plywood over the joists?
What direction should i lay the 2X2's over the first sheet of plywood?
What direction should i lay the 2nd sheet of plywood over the 2X2's?

send_it_all

If I was doing it, I would seriously consider using the 2X2s on top of the joists like furring strips, the laying one layer of plywood in one direction, then the 2nd layer of plywood the opposite direction. That would have a more solid feel than what you plan...

Mischman

Just cover the joists and cross bracing with a 2X2? is a 3" drywall every ~12" strong enough to hold them down and keep the plywood solid?

send_it_all

I would probably go with deck screws instead of drywall, but every 12" should be more than enough. Construction adhesive would add a little strength and possibly help eliminate squeaks, but if someone ever wanted to undo what you are doing, it would be tough.

Mischman

The first layed of plywood goes perpendicular to the joists? The top layed of plywood would be running parallel?

reveivl

What send-it-all said. Unless you're planning on removing it at some point, use the glue. What's going over it? You don't really need two layers of 3/4 ply unless you're putting down natural stone, and it would be cheaper to rip 2x6 into 2-1/4" strips and use one layer of ply.

Drywall screws are for drywall, not structure.

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Mischman

The subfloor around it is 3", dont want a big dip in my floor.

reveivl

What are you putting down on top of the sub, for finish? I understand that you want the floor to be level with existing, but there are easier, and cheaper, ways of doing it than 1-1/2" of plywood.

__________________
From where does knowledge come? If you need to know what is in a box, you could ask someone (not reliable), you could pray, (not useful), you can consult with the scripture (not helpful) or you could open the box (science)

dlcj

I agree with this. put the strips on 16" centers or 12" if your worried about it. And use 1 layer of 3/4" ply. Just wandering why the original subfloor is 3" thick anyway?

JustaFramer

why not use 3/8 plywood layed every 16" in 1.5"x3" pieces then lay 2x2 on top fasten them down and put 1 1/8th ply wood on top?

neolitic

JustaFramer

I don't know why you are giving me the shifty eyes. But you must of neve done a free floating floor?

They were the rave in the mid to late 90's in condos around here.

Mischman

Old house, was originally built with MDF(or some saw dust board, not OSB) and it got rotten so who every fixed it just kept throwing more ply wood over the whole house to make it *even* and *strong*. They did that instead of just pulling up the rotten MDF and replacing it. I pulled up the MDF and crap plywood and made it solid and level.


Its already finished, did it how send said. Ran into a few small complications of one of the joists being cracked and the joists being slightly off level(1/4"). Thanks for the help.

P.s. I used silver exterior grip tight screws.