# Screw pattern and size for 3/4" plywood subfloor?



## amateurplumber (Mar 11, 2013)

Hey there, I'm getting read to screw and glue some subfloor in. I bought subfloor glue and will be putting it on the joists (should I just do a zigzag?) before I screw them in. To screw them in, I was planning on getting #8 2" fully threaded construction screws. 

Is that a good idea? Should I get partially threaded instead? Should I alternate between full and partially threaded? How many inches between the screws?

Thanks a ton guys!


----------



## joecaption (Nov 30, 2011)

Faster, easier, and far cheaper to use 8D ring shanked nails.
If your going to use screws then go with 2-1/2" ceramic coated decking screws.
Us an impact driver not a cordless drill.


----------



## joecaption (Nov 30, 2011)

joecaption said:


> Faster, easier, and far cheaper to use 8D ring shanked nails.
> If your going to use screws then go with 2-1/2" ceramic coated decking screws.
> Use an impact driver not a cordless drill.


Already bought the plywood?
Advantech is a far better subfloor then plywood.
If you have the plywood already it is T & G and 3/4" subfloor rated, right?


----------



## amateurplumber (Mar 11, 2013)

Whoaa, 2 1/2"! I've heard that before but some others told me that size is too large. I do have an impact driver so that's nice. 

I can't use t&g because I had to cut out a weird shaped section that was all rotted. I looked EVERYWHERE (everywhere!) for advantech but couldn't find it.


----------



## JazMan (Feb 17, 2007)

amateurplumber said:


> I can't use t&g because I had to cut out a weird shaped section that was all rotted.


Well then you'll need to block under all the unsupported ends before you install it. Either that, or apply a second sheet over it offset to the first of course.

Jaz


----------



## joecaption (Nov 30, 2011)

Got a picture of this patch?
Always better to cut out a larger area then to just try and make a small patch.
It needs to span at least 2 joist.


----------



## JazMan (Feb 17, 2007)

> It needs to span at least 2 joist.


Right, I forgot to mention that except...... the patch needs to rest on 3 joists. So 32" is the smallest it should be, otherwise you add an underlayment over the sub.

Jaz


----------



## amateurplumber (Mar 11, 2013)

Ok, so, please dont crucify me but this is what I ended up doing. I put a 2x8 under the left and right sides to make a nailing edge. I screwed it into the base of the walls frames and the plywood lips, and glued the crap out of it. Here's an image. It's a little outdated...I added all new insulation and added another tiny strip of nailing edge to the right side. I couldnt do a solid undisturbed length on the right side like I did the left side because there were so many pipes. I sistered the middle joist.

I can still open up the bottom ceiling to add some blocking, but it'll have to be horizontal if i can do it at all. There's a big drain that runs through most of the left side and a few different pipes that go through the right side.


----------



## joecaption (Nov 30, 2011)

Oh boy.
Little blocks of wood will do 0 good.
Subfloor should have been cut out with a toe kick saw even with the bottom plates or at least a sawsall.
Blocking should have been added between the joist.
Nailing plate needed to be added over that drain.
Sure looks like you tried to add to a 2 X 4 under the subflooring on the right, useless. Should have cut the subflooring back and added a 2 X 6 under the bottom plate.
That repair is not going to holdup to a tiled floor.


----------



## VinnieVega (Sep 9, 2012)

joecaption said:


> Oh boy.
> Little blocks of wood will do 0 good.
> Subfloor should have been cut out with a toe kick saw even with the bottom plates or at least a sawsall.
> Blocking should have been added between the joist.
> ...




If he adds blocking between the joists every 10" or so I think it would hold. He could easily add that around the plumbing, and then add nailers later to give more support.

I'd also plan on using a shower pan for this area rather than tile it.


----------

