How do I glue and screw subfloor?

10178 Views 8 Replies 3 Participants Last post by joecaption, Dec 18, 2012

bluefoxicy

Discussion Starter · Dec 18, 2012 (Edited)

Two questions:

http://www.lowes.com/SearchCatalogD...&N=0&newSearch=true&Ntt=construction+adhesive

Which of these things do I need?

What is the appropriate screw spacing?

Screws should be Deckmate 1 1/4 inch #8 Torx drive screws? Or am I supposed to penetrate through the existing subfloor and screw to the joists as well?

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joecaption

· #2 · Dec 18, 2012

http://www.lowes.com/ProductDisplay...gId=10051&cmRelshp=req&rel=nofollow&cId=PDIO1
The liquid nails or the PL will work fine.
I'd strongly suggest you use Advantec 3/4 T X G subflooring not plywood.
It's stonger, 0 chance it's going to delaminite, far more water resistant.
There's also going to be a screwing pattern printed right on the panels. Should be about every 6 to 8".
Your going to need an impact driver, a cordless drill with just be way to slow and not have the torque needed.
I broke down and bought a stand up screw gun, it has to be 100 times faster and a whole lot easyer on my old knees.
When laying it make sure to off set the panels. (first row full lenght, second row first piece get cut in 1/2.)
You do not want to end up with any short pieces on the ends of a row! Each piece needs to be a minumum of 24". Do some measuring before begining, if you see the end will be short just cut something off the first full lenght sheet so the last one will then be longer.
Subflooring must be laid at right angles to the joist.
To speed things along you drop the subfloor on the joist and lay a 2X4 across the joist to use as a tapping block to set them together.
There will always still be a small gap when using T & G that shows, it's suppost to be that way, do not keep trying to close it up.

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bluefoxicy

Discussion Starter · #3 · Dec 18, 2012

http://www.lowes.com/pd_12244-99899...ywood&pl=1&currentURL=?Ntt=plywood&facetInfo=

This is the kind of thing I was looking at. Tongue-and-groove plywood sheathing. I'm unsure if the existing subfloor is thick enough for tile floor and granite counter (though the floor doesn't deflect when holding a pile of tile and 6 bags of thinset--2x8 sistered to 2x10 20 inch CTC for joists, beefy) and I'd like to build it up anyway.

How do I apply the glue? Zig-zag pattern or do I need to trow for complete coverage?

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shazapple

· #4 · Dec 18, 2012

Any tile guy will point you to the Deflectolator http://www.johnbridge.com/vbulletin/deflecto.pl It will tell you if you have a proper structure for tile.

When I did my kitchen I used 3/4" t&g plywood over the existing, along with ditra. I screwed it every 6", sometimes more where there would be a lot of traffic.

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joecaption

· #5 · Dec 18, 2012

No pattern needed, no need to spead it out. I also never use those small tubes, it's avalible in a much larger tube, just going to also have to buy the larger cauking gun. What your going to over pay for those small tubes and the extra time involved will be made up for in the saving from using the larger tube.

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bluefoxicy

Discussion Starter · #6 · Dec 18, 2012

shazapple said:
Any tile guy will point you to the Deflectolator http://www.johnbridge.com/vbulletin/deflecto.pl It will tell you if you have a proper structure for tile.

2x8 sistered to 2x10 so I just gave it as 4x8. It's pine, SYP. 20 CTC, 15 foot span, tells me ceramic is good but natural stone bad; porcelain is a ceramic so I'll take it.

No ideas on Ditra; I'm using cement board.

Thread is about how to put the subfloor layer down anyway, but thanks.

joecaption said:
No pattern needed, no need to spead it out. I also never use those small tubes, it's avalible in a much larger tube, just going to also have to buy the larger cauking gun. What your going to over pay for those small tubes and the extra time involved will be made up for in the saving from using the larger tube.

Yeah I figured for this I'd get the big size caulk gun and big size tube of glue. That's the 28oz normal bigger of the two sizes typically available at a Home Depot or Lowes, right? Not another, ginormous-sized tube?

What do you mean no pattern and no need to spread? I can't just lay a blob down in the middle of the floor... I haven't been able to find any videos or pictures demonstrating how to use construction adhesive to glue an additional subfloor layer (or sometimes people call it underlayment when they're clearly talking about a 5/8 inch thick sheet of wood...).

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joecaption

· #7 · Dec 18, 2012

The only glue that's used is only on the floor joist, never on top of the subflooring.
Underlaymant is never glued down!
The underlayment is attached every 4" on the edges, 6 to 8" in the field.
Make sure the underlaymant is subfloor rated.
Make sure the seams on the underlamnent do not line up with the seams in the subflooring.
DO not try and nail the underlayment to the floor joist, your trying to get 100% contact with the subflooring so there's no flexing.
There must be a layer of thin set layed under the tile board.

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bluefoxicy

Discussion Starter · #8 · Dec 18, 2012

joecaption said:
The only glue that's used is only on the floor joist, never on top of the subflooring.
Underlaymant is never glued down!
The underlayment is attached every 4" on the edges, 6 to 8" in the field.
Make sure the underlaymant is subfloor rated.
Make sure the seams on the underlamnent do not line up with the seams in the subflooring.
DO not try and nail the underlayment to the floor joist, your trying to get 100% contact with the subflooring so there's no flexing.

OKAY!

So, no gluing down additional subfloor layers. 4 inches at the perimeter, then start 6 x 6 in and provide a 6 x 6 field. I assume it is more prudent to begin in the center and work outward, but that's the general pattern. Don't screw into the joists.

Impact driver instead of that insane cordless drill I have. That's a no-brainer... don't want to put screws straight through the workpiece again (the drill/driver was sinking screws straight through cement board; the impact driver at least slows down and switches to impact so I can control it).

Well that simplifies the job. Let's do some quick math... 4 x 8 sheets, 4 inches around the perimeter we'll say starting 1 inch in and doubles on the corner (like on Hardiebacker), with a 6 inch field starting 6 x 6 in. 12 and 24 per side, 72 screws for the perimeter; 84 in the field; 156 total per sheet. For 6 sheets I'm going to need 936 screws. Just over 5lb of #8 star drive 1 1/4 inch screws, $30. (And if I would bother to memorize the division tables for the soroban I could have done the division in my head instantaneously too, instead of just the addition...)

It's going to cost me about $220 to place this underlayment.

Thanks guys!

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joecaption

· #9 · Dec 18, 2012

I use screws in the subfloor and a pneumatic narrow crown staple gun with 1-1/4 staples when laying the subflooring.

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