Increase height of subflooring

thiggins18

I have been remodeling our master bedroom for two months and have run into some unfamiliar territory. I pulled the carpet in the bedroom and the subflooring is 3/4" TG OSB. The master meets up with marble tile in the bathroom and the hallway. The tile is 1" 1/8" higher than the subflooring. After the wife told me, "It will look terrible to have a step in the threshold" I am left with the problem of, how do I raise the subflooring height 1/4-3/8"?

Initially I was going to glue 1/4" cork down and then install the 5" solid maple planks over the cork. I started investigating on the internet and many people have had problems with this type of installation. So what I am leaning towards now is installing 3/8" ply over the subfloor.

My questions are all about installation methods… What is the preferred method?

-Glue and Screw?
-Run parallel or perpendicular to existing subfloor?
-Butt snug or leave gaps on joints?
-Screw Length?
-Should I be trying to hit the floor joists (I already screwed down the OSB with 2" subflooring screws)?

HarryJ

3/8" ply is a good idea

-Glue and Screw? i prefer to staple anything less than 1/2"
-Run parallel or perpendicular to existing subfloor? it doesn't matter as long as you overlap joints at least 6"
-Butt snug or leave gaps on joints? butt is fine
-Screw Length? did i mention staples? 1-1/8" with 1/4" crown
-Should I be trying to hit the floor joists (I already screwed down the OSB with 2" subflooring screws)? not necessary

joecaption

Underlamnet is never glued to the subflooring.
Do not fasten the underlament to the floor joist. Your trying to pull the to together so there's no gap between the floor joist.

oh'mike

Harry and Joe have given you good advice---avoid hitting the floor joists--do not use glue---3/8 inch minimum thickness----screws are fine but slow and expensive---small crown staples (lots of them) are fast--easy and effective---

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oh'mike

DO NOT GLUE---follow directions given by the pros--

This is an open public forum and not all advice is sound and backed by proper education and years of experience---

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framer52

Personally I would not worry about the 1/4" difference in height between the two floors. You will need a transition piece anyway as the two should have 1/2" between the surfaces.

creeper

Where's Bud?

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thiggins18

Ok thanks. Just picked up the stuff to do it right now, 15/32 in. x 4 ft. x 8 ft. 3-Ply Rtd Sheathing is what I'm using... Thats ok right ?

joecaption

Nope, should have been underlament rated.
Sheathing will have unfilled knot holes in the plys, and not enough plys.
I also use a narrow 1-1/2 crown staple when attaching thinner plys. I can set it in automatic and nail a whole sheet in 1 min. and it leaves no dumples or big holes that would need filling it you were laying sheet goods.

thiggins18

So I need the 15/32 In. x 4 Ft. x 8 Ft. BC Sanded Pine Plywood ? When I looked at it it looked like the only diffrence is the sanded pine vs the sheating was the sheeting was sanded... so what your saying is its sanded and filled?

JazMan

Sheathing is not for floors, as Joe said. it might be good enough since you're covering with wood, but............ The willingness to spend less can be costly in the end.

Absolutely wrong answer. The new underlayment must run parallel, but offset to the subfloor. In other words, all subfloor & underlayments should run perpendicular to the joists....always.

And of course no gluing to the subfloor and do not try to "hit" the joists. Of course if you use the right fasteners they will not be long enough to hit the joists. It's usually a good idea to leave an 1/8" gap between sheets and at least 1/4" at perimeter.

Jaz

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thiggins18

Is the difference between the sanded ply and the sheeting ply the sanded is free of voids (and obviously sanded)?

HarryJ

sanded only guaratees free of voids on the surface.

For your specific needs a cheaper standard ply will be great.
The extra benefits from a sanded product is just money flushed down the toilet.

thiggins18

Arggggg Do I have to go to somewhere other than HD or Lowes? The only stuff they have around a 1/2 inch is 15/32 sheathing, 15/32 rated sheathing, and the sanded.

thiggins18

What do you mean by standard plywood?

I've called around to building suppliers and my options are.

CDX yellow pine (sheathing), BCX plywood, ACX plywood, CDX Fire retardent, baltic birch (expensive), and sandply (also expensive).

I guess BCX is certified for use as underlayment.